BURNDY LIBRARY
ChartenJ in 1^1
GIFT OF
Bern Dibner
The Dibner Library
of the History of Science and Technology
SMITHSONIAN INSTITUTION LIBRARIES
ELEMENTS
OF
CHEMICAL PHILOSOPHY.
\
BY
SIR HUMPHRY DAVY, LL. D.
Sec. R. S. Prof. Chem. R. I. and B. A. M. R. I. F. R; S. E. M.R. I. A. Member of the Royal Academy of Stockholm; of the Imperial Med. and Chir. Academy of St. Petersburgh ; of the American Philosophical Society ; and Honorary Member of the Societies of Dublin, Manchester, the Physical Society of Edinburgh, and the Medical Society of London.
BART I. VOL. L
LONDON:
PRINTED FOR J. JOHNSON AND CO. ST. PAUL's CHUKCH-YARD.
1812,
London: printed by W. Bulnaer and Co. Ciev eland-row.
TO
LADY DAVY.
There is no individual to whom I can with so much propriety or so much pleasure dedicate this Work as to you. The interest you have taken in the progress of it, has been a constant motive for my exertions; and it was begun and finished in a period of my hfe which, owing to you, has been the happiest. Regard it as a pledge that I shall continue to pursue Science with unabated ardour. Receive it as a proof of my ardent affection, which must be unalterable, for it is founded upon the admiration of your moral and intellectual qualities.
H. DAVY.
i
t
1
ADVERTISEMENT-
In this Work I have endeavoured as far as it was in my power, to employ the nomencla- ture most in use amongst the chemists of the present day in Britain. In consequence of the progress of discovery, some of the names adopted from the French School of Chemistry now imply erroneous ideas. In such cases I have recurred as often as was possible to the familiar names, or the old names.
In adopting new names, I have been guided by the necessity of the case ; and have applied them only to new substances, or to substances the nature of which had been misunderstood, and which were confounded with other bodies differing from them in their nature.
I may perhaps be censured for having pro- posed to signify the combinations of chlorine or oxymuriatic gas by simple terminations, con- nected with the name of the basis, such as ane and ana ; but these terminations will serve at
vi
ADVERTISEMENT.
least as symbols of the class, and in this way may assist the memory.
In the last Bakerian Lecture, published in the Philosophical Transactions, I have proposed to denominate the combinations of chlorine sup- posed to contain one proportion, by the termi- nation ane, those supposed to contain two by ana, and those containing three by anee. As, how- ever, amongst the metallic combinations of chlo- rine, there are never more than two distinct com- binations belonging to the same metal, I have given the termination ane to the first, and that of ana to the second, without reference to propor- tions ; or where there has been only one, I have used simply ane. If my original proposal should be adopted, it will however be easy to make the corrections, and the cases are very few that will require it. Common salt, which contains two proportions of chlorine, and which in this work is called sodane, will be called sodana ; ferrane will be called ferranea ferranea, ferranee ; and arsenicane must be chan2;ed to arsenicana.
Some persons may chuse rather to use the word chloride, following the analogy of oxide ; but as I have expressed in the Introduction, our nomenclature would have been more simple and
DSI
ADVERTISEMENT. m
useful without any attempt at tlieoretkal ex- pressions of the composition of bodies ; and as the fixed alkalies, earths, and oxides, are similar bodies, and the termination a has been applied to the two first, it might be properly extended to the last.
The word oxide is however now current, I have therefore used it, and have employed Dr. Thomson's method of distinguishing the dif- ferent oxides of the same metal, by prefixing to them syllables derived from the Greek nu- merals ; deutoxide, tritoxide, tetroxide^ signify that the bodies contain two, three, or four pro- portions of oxygene. When the word oxide alone is used, one proportion only of oxygene is supposed to exist in it.
Whatever pains be taken, it will not be pos- sible to make the existina; nomenclature con- forrjaable to the idiom of our language ; and till some general principles for its improvement are agreed to by the enlightened in different parts of Europe, it cannot be expected to be even a philosophical language ; and till a more simple system is adopted, innovation will be censured sometimes perhaps even when it is necessary, and Neology generally brought for- ward as a reproach.
ADVERTISEMENT.
I have in a few instances only, given an ac- count of the experiments, from the results of which the numbers representing the undecom- posed bodies were calculated.
To have given accurate histories of those experiments, would have been incompatible with the object of an elementary book devoted to the 2;eneral truths and methods of the science ; I shall however shortly present them to the publick, in a work containing the details of labours that I have carried on durina. the last twelve years in analytical chemistry.
I have usually given whole numbers, taking away or adding fractional parts, that they may be more easily retained in the memory. When the number was gained from experiments in which a loss might be supposed, I have added fractional parts, so as to make a whole number. Thus the number representing barium,, is nearer 129 than 130; but it is given as 130, because it was deduced from an indirect ex- periment in which a loss of weight was more probable than an increase from any foreign source.
In a future edition of this work, should my imperfect labours be favourably received, I may hope to be able to complete the
ADVERTISEMENT. ix
series of numbers, and to fix some that are doubtful.
I cannot conclude without acknowledging my obligations to my brother Mr. John Davy, for the able assistance he afforded me in the progress of the researches which form the foundation of this treatise.
I have likewise received much useful expe- rimental aid from Mr. E. Davy, and Mr. W. Moore.
The greater number of the experiments were made in the laboratory of the Royal Institution ; and all that were fitted for demons- tration have been exhibited in the Theatre of that useful publick establishment in my annual courses of lectures ; and have been received by the members in a manner which I shall always remember with gratitude.
BerTceley Square^ June 1, 1812.
CONTENTS
Introduction . . . page 1
Historical View of the Progress of Chemistry.
PART I.
ON THE LAWS OF CHEMICAL CHANGES: ON UNDECOMPOUNDED BODIES AND THEIR PRI- MARY COMBINATIONS . . 6l
DIVISION I.
ON THE POWERS AND PROPERTIES OF MAT- TER, AND THE GENERAL LAWS OF CHEMICAL
CHANGES.
Preliminary Observations , , 63
Of the Forms of Matter . . 65
Gravitation . . • 67
Cohesion . . .63
Of Heat, or calorific Repulsion . 6Q
On chemical Attraction, and the Laws of Combination
and Decomposition . ; 98
Of Electrical Attraction and Kepulsion, and their
Relations to Chemical Changes . . 125
On Analysis and Synthesis: on the Circumstances to be attended to in these Operations, and on the Arrangement of undecompounded Bodies 180
CONTENTS,
DIVISION II.
OF RADIANT OR ETHEREAL MATTER.
Of the Effects of radiant Matter, in producing the
Phaenomena of Vision . page 195
Of the Operation of radiant Matter in producing
Heat ..... 201 Of the Effects of radiant Matter in producing chemical
Changes . ; . . 210
Of the Nature of the Motions or Affections of radiant
Matter . . . . 213
DIVISION III.
OFEMPYREALUNDECOMPOUNDED SUBSTANCES, OR UNDECOMPOUNDED SUBSTANCES THAT SUPPORT COMBUSTION, AND THEIR COMBIN-
ATION WITH EACH OTHER.
General Observations . . , 225
OfoxygeneGas . . . 227
Chlorine, or oxy muriatic Gas . . 235
DIVISION IV.
OF UNDECOMPOUNDED INFLAMMABLE OR ACIDIFEROUS SUBSTANCES NOT METALLIC, AND THEIR BINARY COMBINATIONS WITH OXYGENE AND CHLORINE, OR WITH EACH
OTHER.
Preliminary Observations . . 245
Hydrogene Gas, or inflammable Air . 246
Of Azote, or nitrogene Gas . . 255
Of Sulphur . . .271
Of Phosphorus . . . 285
Of Carbon or Charcoal, and the Diamond 299
Of Boron, or the boracic Basis , , 314
CONTENTS.
DIVISION V.
OF METALS; THEIR PRIMARY COMBINATIONS WITH OTHER UNDECOMPOSED BODIES, AND' WITH EACH OTHER.
|
vrPnpral Ohsprvation<5 |
. page 319 |
|
Of Potassium |
321 |
|
Sodium |
S31 |
|
TJarium . . . -L^uX J I.XX ( #9 |
338 |
|
Strontinm |
. 343 |
|
Calcium |
345 |
|
Maenesium |
350 |
|
Aluminum . |
354 |
|
\iliiriniirn |
358 |
|
X^'s 1 V^vJ if U U.J « • |
S60 |
|
Sill Oil in |
362 |
|
T t Iriii m X Lift lU ill « 4 |
364 |
|
fvl n ca npQn m xvj CLii a Li^oU ill • |
366 |
|
i^inc or Zinouni |
373 |
|
Tin^ or Stannum . |
370 |
|
Iron, or Ferrum . . |
. . 384 |
|
TiPari nr T*lnmV>nm |
3Q4. |
|
Antimonv. or Antimonium |
400 |
|
jjibinuiij^ or jjisnjuiiiiuiu |
|
|
Tellurium |
408 |
|
Cobalt, or Cobaltum |
411 |
|
Copper J Cuprum |
415 |
|
l^ickel, or Nickolum |
420 |
|
Uranium . . |
424 |
|
Osmium |
. 426 |
|
Tungsten, or Tungstenum |
427 |
|
Titanium |
430 |
|
Columbium . . |
431 |
|
Cerium . - . |
. . 433 |
|
Palladium • . |
434 |
xiv
CONTENTS^
Iridium . . . page 436
Rhodium . , 437
Mercury, or Mercurium • - 438
Silver, or Argentum . , . 443
Gold, or Aurum . . . 446
Platinum . . . 448
Arsenic, or Arsenicum . , 453
Molybdenum , . . 459
Chromium . . . 462
DIVISION VI.
OF SOME SUBSTANCES, THE NATURE OF WHICH IS NOT YET CERTAINLY KNOWN.
Preliminary Observations . 465 Of the Fluoric Principle . . ih. Of the Amalgam procured from ammoniacal Com- pounds . . . . 473
DIVISION VII.
ON THE ANALOGIES BETWEEN THE UNDECOM- POUNDED SUBSTANCES; SPECULATIONS RE- SPECTING THEIR NATURE; ON THE MODES OF SEPARATING THEM, AND ON THE RELATIONS OF THEIR COMPOUNDS.
Of the Analogies between the undecom pounded Sub- stances; Ideas respecting their nature . 478
Of the Analogies between the primary Compounds, and on their chemical Relations . . 490
On the relative Attractions of the undecomposed Substances for each other . . . 497
On the Methods of separating the undecomposed Bodies from each other . . 499
General Observations; and Conclusion of Part First 502
ERRATA.
49, line 6, add lead.
71, line 3, /or silver tin, read silver and tin. 98, /or IV. read VI.
Ill, last Hne,/or phosphoranee reaflf phosphorana.
11-2, line 24,/or 15 to 1, read 1 to 15.
197, line 23 and 24,/or ordinary rea«f extraordinary, and
for extraordinary read ordinary. 292, first line of the note,/or 13.2 read 13. S.
319, line 7, /or 39 read 38.
320, line 19, erase palladium. 451, line 9,/or 18,5 read 24.
INTRODUCTION.
M GST of the substances belonging: to our globe are constantly undergoing alterations in sensible qualities, and one variety of matter becomes as it were transmuted into another.
Such changes, whether natural or artificial, whether slowly or rapidly performed, are called chemical ; thus the gradual and almost imper- ceptible decay of the leaves and branches of a fallen tree exposed to the atmosphere, and the rapid combustion of wood in our fires, are both chemical operations.
The object of Chemical Philosophy is to as- certain the causes of ail phaenomena of this kind, and to discover the laws by which they are governed.
The ends of this branch of knowledge are the applications of natural substances to new uses, for increasing the coDiforts and enjoy- ments of man, and the demonslration of the
VOL. I. B
2
INTRODUCTION.
order, harmony, and intelligent design of the system of the earth.
The foundations of chemical philosophy, are observation, experiment, and analogy. By observation, facts are distinctly and minutely impressed on the mind. By analogy, similar facts are connected. By experiment, new facts are discovered; and, in the progression of know- ledge, observation, guided by analogy, leads to experiment, and analogy confirmed by expe- riment, becomes scientific truth.
To give an instance. — Whoever will consider with attention the slender green vegetable fila- ments ( Conferva rivularis ) which in the sum- mer exist in almost all streams, lakes, or pools, under the different circumstances of shade and sunshine, will discover globules of air upon the filaments exposed under water to the sun, but no air on the filaments that are shaded. He will find that the effect is owing to the pre- sence of light. This is an observation ; but it gives no information respecting the nature of the air. Let a wine glass filled with water be inverted over the Conferva, the air will collect in the upper part of the glass, and when the glass is filled with air, it may be closed by the hand, placed in its usual position, and an
INTRODUCTION. 3
inflamed taper introduced into it; the taper wiil burn with more brilliancy than in the atmos- phere. This is an experiment. If the pheno- mena are reasoned upon, and the question is put, whether all vegetables of this kind, in fresh or in salt water, do not produce such air under like circumstances, the enquirer is guided hy analogy : and when this is determined to be the case by new trials, a general scientific truth is established — That all Confervae in the sun- shine produce a species of air that supports flame in a superior degree ; which has been shewn to be the case by various minute inves- tigations.
These principles of research, and combina- tions of methods, have been little applied, ex- cept in late times. A transient view of the progress of chemical philosophy will prove that the most brilliant discoveriesj and the happiest theoretical arrangements belonging to it are of very recent origin ; and a few histo- rical details and general observations upon the progress and effects of the science will form, perhaps, no improper introduction to the ele- ments of this branch of knowledge.
The only processes which can be called
chemical, known to the civilized nations of
B 2
4
introduction;
antiquity, belonged to certain arts, such as me- tallurgy, dyeing, and the manufacture of glass or porcelain ; but these processes appear to have been independent of each other, pursued in the workshop alone, and unconnected with general knowledge.
In the early mythological systems of the Egyptian priests, and the Braminsof Hindostan, some views respecting the chemical changes of the elements seem to have been developed, which passed, under new modifications} iato the theories of the Greeks ; but as the most refined doctrines of this enlightened people, concerning natural causes, in their best times, were little more than a collection of vague spe- culations, rather poetical than philosophical, it cannot well be supposed that in earlier ages, and amongst nations less advanced in cul- tivation, there were any traces of genuine science.
The inhabitants of Lower Egypt, where the overflowing of the Nile covered a sandy desert with vegetation and life, might easily adopt the notion, that water, in different modifica- tions, produced all the varieties of inanimate and organized matter ; and this dogma charac" tenzed the earliest school of Greece.
INTHODUeTION.
5
To generalize upon the great forms or powers of nature, as elements, requires only very super- ficial observation; and hence the theories seem to have originated, which have been attributed to Anaximander, and others of the early Greek philosophers, concerning air, earth, water, and fire.
As geometry and the mathematical sciences became improved, mechanical solutions of the changes of bodies were natural consequences, such as the atomic philosophy of the Ionian sect, and the five regular solids assumed by the Pythagoreans as the materials ©f the universe.
In the beginning of the Macedonian dynasty, the school of Aristotle gave a transient atten- tion to the objects of natural science, but the great founder attempted too many subjects to be able to offer correct views of any one series. — And his erroneous practice, that of advancing general principles, and applying them to par- ticular instances, so fatal to truth in all sciences, more particularly opposed itself to the pro- gress of one founded upon a minute examination of obscure and hidden properties of natural bodies.
Theophrastus, the successor of Aristotle, did not, it appears, adopt the sublime, though purely
6
INTRODUCTION.
specujative doctrine of his master, the identity of matter, and its diversity of form;* — for he says, ill the beginning of his book concerning fossils, ' stones are produced from earth, metals from water. 'i — How such a notion as the last could have been formed, it is difficult to dis- cover ; yet, Theophrastus is perhaps the best observer amongst the ancients, whose works are in our possession, and the theories of this distinguished teacher, who is said to have had 9. class of 2000 pupils, cannot be considered as an unfavourable specimen of the theoretical physics of the age.
In all pursuits which required only the na- tive powers of the intellect, or the refinements of taste, the Greeks were pre-eminent ; — their literature, their works of art, offer models which have never been excelled. They possessed, as if instinctively, the perception of every thing beautiful, grand, and decorous. As philoso- phers, they failed not from a want of genius, or even of application, but merely because they pursued a false path, — because they reasoned
* 'E'TTH^h i'B tj (pt/o-K, ^»%aJs-, TO T8 sTJ'o; no.) ri vXrj. Aristotelis Natural. Auscult. Lib. ii. 495, fol. Par. l654.
yh<i AtSof Tt %aX oa-a, hi^m cri^iTToTEjja, Theophrasti de Lapi- dibus. Lug. Br. l6l3.
introduction;
more upon an imaginary system of nature, than upon the visible and tangible universe.
It will be in vain to look in the annals of Rome for science, that did not exist in Greece. The conquerors became the pupils of the con- quered ; and the Romans did little more than clothe the systems of their masters in a new dress, and adapt them to a new people.
The grand, but unequal poem of Lucretius, contains the abstract of the opinions of Epi- curus, compared with those of other celebrated teachers. The Natural History of Pliny, is a collection from all sources, but principally from Theophrastus and Aristotle. The details from his own observation are more interesting when they relate to artificial, than when they refer to natural operations ; the speculative no- tions are of the rudest kind. The earlier phi- losophical work of the Romans, as if indicative of the youth of the people, is marked by power and genius, by boldness and incorrectness ; the later, as if it belonged to their old age, by gar- rulity, copious and amusing anecdote, superr stitious notions, and vulgar prejudices.
Some of the historians of this science,* in
* Many of the alchemical writers derive alchemy from Tubal Cain ; others from Hermes Trismegistus, the Mercury
8
INTRODUCTION.
their zeal for the honour of its antiquity, hare indeed endeavoured to find instances of an ac- quaintance with some doctrines of practical chemistry, atleast, amongst theancients. — Thus Democritus is quoted by Laertius as having employed himself in processes for imitating gems, and for softening and working ivory. Caligula is said to have made experiments with the view of extracting gold from orpiment. — Dioscorides, who is supposed to have been physician to the celebrated Cleopatra, has described the process of subliming mercury from its ores. — Even Cleopatra herself, on the evidence of such circumstances, might be considered as an experimenter, because, in the madness of profusion, she dissolved a pearl in vinegar, and made a nauseous draught of a
of the Greeks. The first writing specifically on a chemical subject, is a manuscript supposed to be of the fifth century, by Zosimus, on the art of making gold and silver; which was in the king's library at Paris. Suidas, who wrote in the ninth or tenth century, mentions Diocletian as having burnt the books of the Egyptians concerning the chemistry of silver and gold : « TTEpt •xy^i'io.ti ufyvpa xot) x^van." Lexicon, Tom. i. pag. 595.
For a minute investigation of the claims of the ancients to chemical knowledge, the reader may consult Borrichius de Ortu et Progress. Choem. Bergman. Opuscula, vol. IV. de pri- iRordiis Chasm, and Lenglet Dufrenoy, Histoire de la Philoso-^ phie hermetique.
INTRODUCTION. 9
costly and^ beautiful substance; but it is idle to relate such circumstances as indications of science. If chemical operations had been known to any extent, beyond their mere relations to the arts, some mention of them might have been expected in the medical writings of those times ; but not even distillation is noticed in the M^orks of Hippocrates or Galen; and the same Dioscorides who has been just alluded to, and who probably possessed vv^hatever know- ledge was at that time extant in Egypt^ recom- mends the use of a fleece of wool or a sponge, for collecting the products from boiling or burning substances.*
The origin of chemistry, as a science of experiment, cannot be dated farther back than the seventh or eighth century of the Christian era, and it seems to have been coeval with the short period in which cultivation and improve- Kient were promoted by the Arabians.
The early Mahometans endeavoured to de- stroy all the records of the former progress of the human mind ; and, as if to make com- pensation for this barbarian spirit, the same people were destined, in a more adranced period, to rekindle the light of letters, and to
* Dioscordis liber i. de picino oleo, pag 52.
10
INTRODUCTION.
become the inventors and cultivators of a new science.
The early nomenclature of chemistry de- monstrates how much it owes to the Arabians. — The words alcohol, alkahest, aludel, alembic, alkali, require no comment.
The first Arabian systematic works on chemistry are said to have been composed by Geber in the reigns of the caliphs Almainon and Almanzor. The preparation of medicines seems to have been the primary object in this study ; and Rhases, Avicenna, and Avenzoar, who have described various chemical opera- tions in their works, were the celebrated phy- sicians of the age.
Amongst a people of conquerors, disposed to sensuality and luxury even from the spirit of their religion, and romantic and magnificent in their views of power, it was not to be ex- pected that any new knowledge should be followed in a rational and philosophical man- ner ; and the early chemical discoveries led to the pursuit of alchemy, the objects of which were to produce a substance capable of con- verting all ©tlier metals into gold ; and an uni- versal remedy calculated indefinitely to prolong the period of human life
INTRODUCTION.
11
Reasonings upon the nature of the metals, and the composition of the philosopher's stone, form a principal part of the treatises ascribed to Geber ;* and the disciples of the School of Bagdat seem to have been the first professed alchemists.
It required strong motives to induce men to pursue the tedious and disgusting processes of the furnace ; but labourers could hardly be wanting, when prospects so brilliant and mag- nificent were oflfered to them ; the means of procuring unbounded wealth ; of forming a paradise on earth ; and of enjoying an immor- tality depending on their own powers.
The processes supposed to relate to the transmutation of metals, and the elixir of life,
* The library of the British Museum contains several works bearing the name of Geber: amongst them are, De Alchemia argentea, Speculum Alchemiae, et de Inventione perfectionis : but they appear to be compilations formed by alchemists of the loth and l6th centuries. Arsenic, mer- cury, and sulphur, are considered in them as elements of the metals ; distillation is distinctly described. Alcohol, cor- rosive sublimate, and different saline combinations of iron, tin, copper, and lead, are mentioned in them; but they abound in obscure descriptions of mysterious processes, and contain an account of some impracticable experiments. — The Liber Fornacum is the most intelligible pari of the works ascribed to Geber ; it contains a description of several metalur- ^ical operations, and of the common apparatus of the assaycr.
12
INTRODUCTION.
* were probably jErst made known to the Europe cans during the time of the crusades— and many of the warriors who, animated with visionary plans of conquest, fought the battles of their religion in the plains of Palestine, seemed to have returned to their native coun- tries under the influence of a new delusion.
The public spirit in the West, was calculated to assist the progress of all pursuits that carried with them an air of mysticism. Warm with the ardor of an extending and exalted religion, men were much more disposed to believe than to reason ; — the love of knowledge and power is instinctive in the human mind ; in darkness it desires light, and follows it with enthusiasm even when appearing merely in delusive glimmerings.
The records of the middle ages contain a great variety of anecdotes relating to the trans- mutation of metals, and the views or pretensions of persons considered as adepts in alchemy: these early periods constitute what may be re- garded as the heroic or fabulous ages of che- mistry. Some of the alchemists were low impostors, whose object was to delude the cre- dulous and the ignorant ; others seemed to have deceived themselves with vain hopes ; but all followed the pursuit as a secret and myste-
INTRODUCTION. 13
Tious study. T,h« processes were communicated only to chosen disciples, and being veiled in the most enigmatic and obscure language, their im- portance was enhanced by the concealment. In all times men are governed more by what they desire or fear, than by what they know ; and in this age it was peculiarly easy to deceive, but difficult to enlighten, the public mind ; truths were discovered, but they were blended with the false and the marvellous; and another era was required to separate them from absurdities, and to demonstrate their importance and uses
Arnald of Villa Nova, who is said to have died in 1250, was one of the earliest European Enquirers who attended to chemical opera tions. In the edition of the works ascribed to him, published at Leyden in I509,* there are several treatises on alchemical subjects, which shew that he firmly believed in the transmu- tation of metals ; the same opinions are attri- buted to him and to Geber ; and he seems to have followed the study with no ©thcr views than those of preparing medicines, and attempt^ ing the composition of the philosopher's stone.
Raymund Lully of Majorca is said to have been a disciple of Arnald, and applied himself
* Opera Arnaldi de Villa Nova, fol, 1509,
14
INTRODUCTION.
much more than his instructor to philosophy ; but the works on general science, ascribed to him, are more abundant in abstract metaphy- sical propositions, than in facts; he followed, in his physical views, the plan of Aristotle, and our opinion of his chemical talents cannot be very exalted, if the alchemical treatises bearing his name be regarded as genuine documents.
Arnald and LuUy are both celebrated by the vindicators of alchemy, as having been certainly possessed of the secret of transmutation. Arnald is said to have converted iron into gold at Rome ; and it is pretended that Lully performed a si- milar operation before Edward I. in London, of which gold nobles were said to have been made.*
That the delusions of alchemy were ardently pursued at this time may be learnt from a reference to the public acts of these periods. Pope John the S2d, who was raised to the pon- tificate in the year 13 16, openly condemned the alchemists as impostors, and the bull begins by stating, that *' they promise what they do not perform and in England an act of Par- liament was passed in the fifth year of the reign of Henry IV. prohibiting the attempts at transmutation, and making them fclonious.f
* Bergman. Opuscula, Tom. IV. pag. 126.
t Lord Coke calls this act the shortest he ever met with.
INTRODUCTION.
15
Even in these times, however, there were some few efforts to form scientific views. In the beginning of the thirteenth century, Roger Bacon of Oxford applied himself to experi- ment, and his works offer proofs of talents, industry, and sagacity. He tv^as a man of a truly philosophical turn, desirous of investigating nature, and of extending the resources of art, and his enquiries offered some very extraordinary combinations ; but neither his labours, nor those of Albert of Cologne, his contemporary, who appears to have been a genius of a kindred character, had any con- siderable influence on the improvement of their age. The wonders performed by the ex- perimental art were attributed by the vulgar to magic ; and at a time when knowledge be- longed only to the cloister, any new philosophy was of course regarded even by the learned with a jealous eye.
It would be a labour of little profit to dwell upon the works of the professed alchemists of the fourteenth and fifteenth centuries, of
5 H. IV. Statutes at large, Vol. I. page 457. " None from henceforth shall use to multiply gold or silver, or use the craft of multiplication, and if any the same do, he shall incur the pain of felony."
16
INTRODUeilON.
Richard and Ripley in England, Isac in Hol- land, Pico of Mirandula and Koffsky, in Poland. The works attributed to these persons are of a similar stamp,* and contain nothin*; which can either instruct or amuse an intelligent reader. Basil Valentine of Erfurt deserves to be sepa- rated from the rest of the enquirers of this age, on account of the novelty and variety of his experiments on metallic preparations, par- ticularly antimony: in his Currus triumphalis Antimonii he has described a number of the combinations of this metal. He used the mineral acids for solutions, and seems to have been one of the first persons who observed the production of ether from alcohol. He flourished about the year 14 i 3.
Cornelius Agrippa, who was born at Cologne in 14865 openly professed magic, and endea- voured to connect together judicial astrology, the hermetic art, and metaphysical philosophy ; and he was followed by Paracelsus, in Switzer- land, and Digby, Kelly, and Dee, in England.
The first Arabian Alchemists seem to have adopted the idea, that the elements were under
* Amongst them areRicardi AngU Libellus, wspt Opus Saturni Johan. Isac, Compounde of Alchemy bj George Ripley.
INTRODUCTION, 17
the dominion of spiritual beings, who might he submitted to human power ; and the notions of fairies and of genii, which have been depicted with so much vividness of fancy and liveliness of description in the Thousand and One Nights, seem to have been connected with the pursuit of the science of transmutation, and the production of the elixir of life. The specu- lative ideas of the Arabians were more or less adopted by their European disciples. The Rosi- crucian philosophy, in which gnomes, sylphs, salamanders, and nymphs were the spiritual agents, supposed capable of being governed or enslaved by man, seems to have originated with the Alchemists of this period ; and Agrippa, Paracelsus, and their followers, above men- tioned, all professed to believe in supernatural powers, in an art above experiment, in a system of knowledge not derived from the senses. It would be a tedious and useless task, to describe all the absurdities in the opinions and practices of this school. Paracelsus alone deserves par- ticular notice, from the circumstance of his being the first public lecturer on chemistry in Europe, and from the more important cir- cumstance of his application of mercurial pre- parations to the cure of diseases. The Magis-
VOL. I. C
is iNTROiilJdtlbN.
trates of Basle established a professor's chair for their countryman, but he soon quitted an oc- cupation in which regularity was necessary, and spent his days in wandering from place to place, searching for, and revealing secrets. He pretended to confer immortality^ by his inedicines, and yet died at the age of 49, at Saltsburg, in the year I54I.*
The enthusiasm of this man almost supplied his want of scenius. He formed a number of new preparations of the metals, which were Studied and applied by his disciples ; his exag- gerated censure of the methods of the ancients, and of the systems of his day, had an effect in diminishing their popularity ; one error was expelled by another ; and it is a great step to- wards improvement, that men should knew they have been in delusion.
Van Helmont, of Brussels, born in I58'§,t was formed in the school of Alchemy, and his mind was tinctured with its prejudices ; but his views concerning nature and the elements were distinguished by nmch more philosophi- 'cal aeutetiess, and more sagacity, than those of any former writer. He is the first person who
^ Dictionnaire Historique, par Moreri, Tomeviii. pag»6^4. 1 1-bid Tom. v. pag, 570.
INTRODUCTION. 19
seems to have had any idea respecting elastic- fluids, different from the air of the atmosphere and he has distinctly mentioned three of these substances, to which he applied the term gases ; namely, aqueous gas or steam, unctuous or in- flammable gas, and gas from wood or carbonic acid gas. Van Helmont developed some accu- rate views respecting the permanent elasticity of air, and the operation of heat upon it ; and a sketch of a curious instrument very similar to the differential thermometer, is to be found in his works.*
Van Helmont has used a term not so appli- cable or intelligible as gas, namely, Bias ; which, he supposed to be an influence derived from the heavenly bodies, of a most subtile and etherial nature ; and on the idea of its opera- tions in our terrestial system, he has endea- voured to found the vindication of astrology.-f-
At this period there was no taste in the pub- lic mind to restrain vague imaginations. There were no severe critics to correct the wander- ings of genius. The systems of logic, adopted in the schools were founded rather upon the
* Johan Baptist. Van Helmont, Opera Omnia, 4to. pag. 6l. article Aer. •j" Ibid. pag. 114.
C S
20
INTRODUCTION.
analogies of words, than upon the relations of things ; and they were more calculated to con- ceal error, than to discover truth. — Till the revival of literature in Europe, there was no at- tempt at philosophical discussion in any of the sciences ; the diffusion of letters gradually brought the opinions of men to the standard of nature and truth ; failures in the experi- mental arts produced caution, and the detection of imposture created rational scepticism.
The delusions of Alchemy were exposed by Guibert, Gassendi, and Kepler. Libavius an- swered Guibert in a tone which demonstrated the weakness of his cause. This person, who died in 1616, was the last active experimentalist who believed that transmutation had actually been performed ; and in the beginning of the 1 7 th century the processes of rational chemistry were pursued by a number of enlightened persons in different parts of Europe.
A metallurgical School had before this time been founded in Germany. George Agricola published, in 1542, his twelve books, de Re Metallica, or, on the methods of extracting and purifying the useTul metals ,- and he was followed by Lazarus Erckern. Assay Master General of the Empire of Germany, whose
INTRODUCTION. 51
ivorts, brought forward in 15745 contain a number of useful practices detailed in a simple and perspicuous manner.
Lord Bacon happily described the Alche- mists as similar to those husbandmen who in searching for a treasure supposed to be hidden in their land, by turning up and pulverising the soil, rendered it fertile; in seeking for brilliant impossibilities, they sometimes dis- covered useful realities ; and in speaking of the chemistry of his time, he says, a new philoso- phy has arisen from the furnaces, which has confounded all the reasonings of the ancients. This illustrious man himself pointed out many important objects of chemical enquiry ; but he was a still greater benefactor to the science, by his developement of the general system for improving natural knowledge. Till his time there had been no distinct views concernincr the art of experiment and observation. Lord Bacon demonstrated how little could be effected by the unassisted human powers, and the weakness of the strongest intellect even without artificial resources. He directed the attention of inqui- rers to instruments for assisting the senses, and for examinins; bodies under new relations. He taught that Man was but the servant and
t
INTRODUCTION.
interpreter of Nature ; capable of discovering truth in no other way but by observing and imitating her operations : that facts were to be collected and not speculations formed : and that the materials for the foundations of true ystems of knowledge were to be discovered, not in the books of the ancients, not in meta- physical theories, not in the fancies of men, but in the visible and tangible external world.
Though Van Helmonthad formed some just ' notions respecting the properties of air, yet his views were blended with obscure and vas;ue speculations, and it is to the disciples of Gal- liljeoj that the true knowledge of the mecha- nical qualities and agencies of elastic fluids is owing. After Torricelli and Pascal had shewn the pressure and weight of the atmosphere, the investigation of its effects in chemical opera- tions became an obvious problem.
John Rey is generally quoted as the first person who shewed by experiments that air is fixed in bodies during calcination : but it ap- pears from the work of this acute and learned man that he reasoned upon the processes of others, rather than upon his own observations.
He quotes Fachsius, Libavius, Cesa]pin,and Cardan, as having ascertained the increase of
INTRODUCTION. St$
weight of lead during its conversion into a calx,* and he mentions an experiment of Hammerus Poppius, who found that antimony calcined by a burning-glass, notwithstanding th^ loss of vapours, yet was heavier after the process,
Rey ridicules the various notions of the Al« chemists on the cause of this phsenomenon ; an4 ascribes it to the union of air with the metal ; he supposes that air is miscible with other bodies besides metals, and states distinctly that it may be expelled from water.
The observations of John Rey seem to have excited no attention amongst his cotemporaries. The philosophical spirit was only beginning to animate chemistry, and the labourers in this science, occupied by their own peculiar pro- cesses, were little disposed to listen to the rea- sonings of an enquirer in general science ; yet, though the most active of the forms of matter were neglected in the processes of tlie operative chemists of this day, and consequently no just views formed by them, still they discovered a number of important facts respecting the com- binations and agencies of solid and fluid bodies.
* Sur la Recherche de la cause par kquelle Estain et le Plomb au^pagntent de poids quaiid on les calcine. A Baiis 1630.
54 INTRODUCTION!.
Glauber at Amsterdam, about !640, mad» known several neutral salts, and several conr- pounds of metallic and vegetable substances, Kunckel in Saxony and Sweden, pursued tech- nical chemistry with very great success, and was the first person who made any philosophical experiments upon phosphorus, which was ac- cidentally discovered by Brandt in 16^9.* Barner in Poland, and Glaser in France, pub- lished elementary books on the. science, and Borichius in Denmark, Bohn at Leipzic, and Hoffman at Halle pursued speciSc scientific in- vestigations with much zeal and success ; and Hoffm an was the first person who attempted the philosophical analysis of mineral waters.
About the middle of this century likewise mathematical and physical Investigations were pursued in every part of the civilized world with an enthusiasm before unknown. The new mode of improving knowledge by collecting facts, associated together a number of labourers in the same pursuit. It was felt that the whole of nature was yet to be investigated, that there were distinct subjects connected with utility and glory, sufficient to employ all enquirers, yet tending to the common end of promoting the * Horaberg, Mem. Acad. Paris, Tom. x. pag. 58.
INTRODUCTION
progress of the human mind. Learned bodies were formed in Italy, England, and France, for the purpose of the interchange of opinions, the combination of labour and division of expense in performing new experiments, and the ac- cumulation and diffusion of knowledge.
The Academy del Cimento was established in 1651 under the patronage of the Duke of Tuscany ; the Royal Society of London, in 1660 ; the Royal Academy of Sciences of Paris, in 1666. And a number of celebrated men, who have been the sireat luminaries of the different departments of science, were brought together or formed in these noble establishments. The ardour of scientific investigation was excited and kept alive by sympathy: taste was improved by discussion, and by a comparison of opinions. The conviction that useful discoveries would be appreciated and rewarded, was a constant stimulus to industry, and every field of enquiry was open for the free and unbiassed exercise of the powers of genius.
Boyle, Hooke, and Slare, were the principal early chemical investigators attached to the Royal Society of London. Homberg, Geoffroy, and the two Lemerys, a few years later, dis" tinguished themselves in France*
S6 INTRODUCTION.
Otto de Guericke of Magdeburgh invented the air pump ; and this instrument, improved by Boyle and Hooke, was made an important apparatus for investigating the properties of air. Boyle* and HQoke,+ from their experi- ments, concluded that air was absolutely ne- cessary to combustion and respiration, and that one part of it only was employed in these pro- cesses. And Hooke formed the sagacious con- clusion, that this principle is the same as the substance fixed in nitre, and that combustioi; is a chemical process, the solution of the burning body in elastic fluid, or its union with this matter.
Mayow of Oxford, in 1674, published his treatises on the nitro-atrial spirit, in which he advanced opinions similar to those of Boyle and Hooke, and supported them by a number of original and curious experiments ;:|: but his work, though marked by strong ingenuity, abounds in vague hypotheses. He attempted to apply the imperfect chemistry of his day to
* Boyle's Works, Vo. iv. page 90.
f Hooke's Micrographia, page 45, 104, 105.
X Tract, p. 28. He has particularly assigned the cause of the calcination of metals, " Quippe vix concipi potest unde augmentum illud antimonii nisi a particulis nitro Mreis i§- »eisque inter calcinajajlum fixis procedat."
IJTTRODUGTION. 27
physiology ; his failure was complete, but it was the failure of a man of genius.
Boyle was one of the most active experi** menters, and certainly the greatest chemist of his age. He introduced the use of tests or reagents, active substances for detecting the presence of other bodies : he overturned the ideas which at that time were prevalent, that the results of operations by fire were the real elements of things, and he ascertained a num- ber of important facts respecting inflammable bodies, acids, alkalies, and the phcenomena of combination ; but neither he nor any of his contemporaries endeavoured to account for the changes of bodies by any fixed principles'.' The solutions of the phasnomena were at- tempted either on rude mechanical notions, or by occult qualities, or peculiar subtile spiritjS or ethers supposed to exist in the different bo- dies.— And it is to the same great genius who developed the laws that regulate the motions of the heavenly bodies, that chemistry owes the first distinct philosophical elucidations of the powers which produce the changes and appa^ rent transmutations of the substances belon<r- ing to the earth.
Sugar dissolves in water, alkalies unite with acids, metals dissolve in acids. Is mi 'ikk^ says
I
2$ INTRODUCTION.
Newton, on account of an attraction between their particles ? Copper dissolved in aquafortis is thrown down by iron. Is not this because the particles of the iron have a stronger at- traction for the particles of the acid, than those of copper ; and do not different bodies attract each other with dijBTerent degrees of force ? *
A few years after Newton had brought for- wards these sagacious views, the elder Geoffroy endeavoured to ascertain the relative attractive powers of bodies for each other, and to arrange them in an order in which these forces, which he named, affinities, were expresed.+
Chemistry had scarcely begun to assume the form of a science, when the attention of the most powerful minds were directed to other objects of research the same great man who bestowed on it its first accurate principles, in some measure impeded its immediate progress, by his more important discoveries in optics, mechanics, and astronomy
These objects of the Newtonian philosophy were calculated by their grandeur, their simpli- city, and their importance, to become the study of the men of most distinguished talents ; the
* Newton's Works, quarto, Tom. iv. page 242. t Mfemoires del' Academic, 17I8, page 256.
INTRODUCTION. S9
effect that they occasioned on the scientific mind may be compared to that which the new sensations of vision produce on the blind re- ceiving sight; — they. awakened the highest in- terest, the most enthusiastic admiration, and for nearly half a century, absorbed the attention of the most eminent philosophers of Britain and France.
Germany still continued the great school of practical chemistry, and at this period it gained an ascendancy of no mean character over the rest of Europe in the philosophy of the science. Beccher, who was born at Spires in I645, after having studied with minute attention, the ope- rations of metallurgy, and the phaenomena of the mineral kingdom, formed the bold idea of explaining the whole system of the earth by the mutual agency and changes of a few ele- ments. And by supposing the existence of a vitrifiable, a metallic, and an inflammable earth, he attempted to account for the various produc- tions of rocks, crystalline bodies, and metallic veins, assuming a continued interchange of principles between the atmosphere, the ocean, and the solid surface of the globe, and consi- dering the operations of nature as all capable ©f being imitated by art.
so NTRODUCTION.
The Phfsica suhterranea, and the Oedipus chemicus of this author, are very extraordinary productions." They display the efforts of a vi- gorous mind, the conceptions of a most fertile imagination, but the conclusions are too rapid- ly formed ; there is a want of logical precision in his reasonings ; the objects he attempted v^ere grand, but his means of execution compa- ratively feeble. He endeavoured to raise a per- fect and lasting edifice upon foundations too Weak, from materials too scanty and not suf- ficiently solid ; and the work, though magni- ficent in design, was rude unfinished and feeble, and rapidly fell into decay.
Beccher added very little to the collection of chemical experiments, but he improved the instruments of research, simplified the mani- pulations, and by the novelty and boldness of 'his speculations, excited enquiry amongst his disciples.
His most distinguished follower was George Ernest Stahl, born in 1660, who soon attained a reputation superior to that of his master, and developed doctrines which for nearly a century constituted, the theory of chemistry of the whole of Europe.
Albertus Magnus had advanced the idea thact
INTRODUCTION. 3^
the mfetals were earthy substances impregnated with a certain inflammable principle. Becchet supported the idea of this principle, not only as the cause of metallization, but likewise of combustibility : and Stahl endeavoured, by a number of ingenious and elaborate experiments, to prove the existence of phlogiston, as it was called, and to explain its agencies in the phaenomena of nature and art.
'Glauber, about fifty years before Stahl begafi liis labours, had discovered the combination of fossil alkali and sulphuric acid, which still bears his name. And Stahl, in operating upon this body, thought he had discovered the proof, tliat the inflammability not only of metals, but likewise of all other substances, was owing to the same principle. Charcoal is entirely dis- sipated or consumed in combustion, therefore, says this philosopher, it must be phlogiston nearly 'pure ; by heating charcoal with metallic earths, they become metals ; therefore they are compounds of metallic earths and phlogis- ton : by heating Glauber's salt, which consists of sulphuric acid and fossil alkali, with charcoal, a compound of sulphur and alkali is obtained ; therefore sulphur is an acid combined with phlogiston. Stahl entirely neglected the che-
3S INTRODUCTION.
mical influence of air on these phenomena ; and though Boyle had proved that phosphorus and sulphur would not burn without air, and had stated that sulphur was contained in sul- phuric acid, and not the acid in sulphur, yet the ideas of the Prussian school were received without controversy. Similar opinions were adopted in France by Homberg and Geoffroy, who assumed them without reference to the views of the Prussian philosopher, and opposed them to the more correct and sagacious views of the English school of chemistry.
Though misled in his general notions, few men have done more than Stahl for the pro- gress of chemical science.— His processes were, many of them, of the most beautiful and satis- factory kind : he discovered a number of properties of the caustic alkalies and metallic calces, and the nature of sulphureous acid ; he reasoned upon all the operations of che- mistry in which gaseous bodies were not con- cerned, with admirable precision. He gave an axiomatic form to the science, banishing from it vague details, circumlocutions and enigmatic descriptions, in which even Beccher had too much indulged ; he laboured in the spirit of the Baconian school, multiplying in*
INTRODUCTION. 33
Stances, and cautiously making inductions, and appealing in all cases to experiments which, though not of the most refined kind, wer« more perfect than any which preceded them.
Dr. Hales, about 17 24, resumed the investi- gations commenced with so much success by Boyle, Hooke, and Mayow; and endeavoured to ascertain the chemical relations of air to other substances, and to ascertain by statical expe- riments the cases in nature, in which it is absorbed or emitted. He obtained a number of important and curious results ; but, misled by the notion of one elementary principle con- stituting elastic matter, and modified in its properties by the effluvia of solid or fluid bodies, he formed few inferences connected with the refined philosophy of the subject: he disengaged, however, elastic fluids from a number of substances, and drew the con- clusion that air was a chemical element in many compound bodies, and that flame resulted from the action and re-action of serial and sulphurous particles.*
In 1756 Dr. Black publisiied his admirable researches on calcareous, magnesian, and al- kaline substances, by which he proved the
• Hales' Statical Essays, 2d ed. 8vo. Vol. i, pag. 315. VOL. I. D
34 INTRODUCTION.
existence of a gaseous body, perfectly distinct from the air of the atmosphere. He shewed that quicklime differed from marble and chalk by containing this substance, and that it was a weak acid, capable of being expelled from alkaline and earthy substances by strong acids.*
Ideas so new and important as those of the British philosopher, were not received without opposition ; several German enquirers endea- voured to controvert them. . Meyer attempted to shew that limestones became caustic, not by the emission of elastic matter, but by com- bining with a peculiar substance in the fire ; but the loss of weight was perfectly inconsistent with this view: and Bergman atUpsal, Macbride in Ireland, Keir at Birmingham, and Cavendish in London, demonstrated the correctness of the opinions of Black; and a few years were suffi- cient to establish his theory upon immutable foundations.
The knowledge of one elastic fluid different from air, immediately led to the enquiry whether there might not be others. The pro- cesses of fermentation which had been observed
* Essays and Observations Physical and Literary, vol. ii. page 1 59,
INTRODUCTION. 35
by the ancient chemists, and those by which Hales had disengaged and collected elastic substances, were now regarded under a novel point of view ; and the consequence was, that a number of new bodies, possessed of very ex- traordinary properties, were discovered.
Mr. Cavendish, about 1765, invented an ap- paratus for examining elastic fluids confined by water, which has been since called the hydro-pneumatic apparatus. He discovered inflammable lair, and described its properties ; he ascertained the relative weights of fixed air, inflammable air, and common air, and made a number of beautiful and accurate experiments on the properties of these elastic substances.
Dr. Priestley, in I771j entered the same in- teresting path of enquiry ; and principally by repeating the processes of Hales, added a number of most important facts to this depart- ment of chemical philosophy. He discovered nitrous air, nitrous oxide, and dephlogisticated air; and by substituting mercury for water in the pneumatic apparatus, ascertained the existence of several aeriform substances, which are rapidly absorbable by water, muriatic acid air, sul- phurous acid air, and ammonia.
Whilst a new branch of the science was
$6
INTRODUCTION.
making this rapid progress in Britain, the che» mistry of solid and fluid substances was pursued with considerable zeal and success in France and Germany ; and Macquer, Rouelle, Mar- graff, and Pott, added considerably to the knowledge of fosslle bodies, and the proper- ties of the metals. Bergman, in Sweden, de- veloped refined ideas on the powers of chemi- cal attraction, and reasoned in a happy spirit of generalization on many of the new phaeno- mena of the science ; and in the same country Scheele, independently of Priestley, discovered several of the same aeriform substances : he ascertained the composition of the atmosphere; he brought to light fluoric acid, prussic acid, and the substance which has been improperly called oxymuriatic gas.
Black, Cavendish, Priestley, and Scheele, were undoubtedly the greatest chemical dis- coverers of the eighteenth century ; and their merits are distinct, peculiar, and of the most exalted kind. Black made a smaller number of original experiments than either of the other philosophers ; but being the first labourer in this new department of the science, he had greater dilEcukies to overcome. His me* ihods are distinguished for their simplicity,
INTRODUCTION.
37
his reasonings are admirable for their pre- cision; and his modest, clear, and unaffected manner, is well calculated to ~ impress upon the mind a conviction of the accuracy of his processes, and the truth and candour of his narrations.
Cavendish was possessed of a minute know- ledge of most of the departments of Natu- ral Philosophy ; he carried into his chemical
researches a delicacy and precision, which have never been exceeded: possessing depth
and extent of mathematical knowledge, he reasoned with the caution of a geometer upon the results of his experiments : and it may be said of him, what, perhaps, can scarcely be said of any other person, that whatever he accomplished, was perfect at the moment of its production. His processes were all of a finished nature ; executed by the hand of a master, they required no correction ; the accu- racy and beauty of his earliest labours even, have remained unimpaired amidst the progress of discovery, and their merits have been illus- trated by discussion, and exalted by time.
Dr. Priestley began his career of discovery without any general knowledge of chemistry, and with a very imperfect apparatus. His
3^
INTRODUCTION.
characteristics were ardent zeal and the most unwearied industry. He exposed all the sub- stances he could procure to chemical agencies, and brought forward his results as they oc- curred, without attempting logical method or scientific arrangement. His hypotheses were usually founded upon a few loose analogies ; but he changed them with facility ; and being framed without much effort, they were relin- quished with little regret. He possessed in the highest degree ingenuousness and the love of truth. His manipulations, though never very refined, were always simple, and often inge- nious. Chemistry owes to him some of her most important instruments of research, and many of her most useful combinations; and no single person ever discovered so many new and cu- rious substances.
Scheele possessed in the highest degree the faculty of invention ; all his labours were in- stituted with an object in view, and after happy or bold analogies. He owed little to fortune or to accidental circumstances : born in an ob- scure situation, occupied in the duties of an irksome employment, nothing could damp the ardour of his mind or chill the fire of his ge- nius : with rery small means he accomplished
INTRODUCTION. S9
very great things. No difficulties deterred him from submitting his ideas to the test of experiment. Occasionally misled in his views, in consequence of the imperfection of his ap- paratus, or the infant state of the inquiry, he never hesitated to give up his opinions the moment they were contradicted by facts. He was eminently endowed with that candour which is characteristic of great minds, and which induces them to rejoice as well in the detection of their own errors, as in the dis- covery of truth- His papers are admirable models of the manner in which experimental research ought to be pursued ; and they con- tain details on some of the most important and brilliant phasnomena of chemical philosophy.
The discovery of the gasses, of a new class of bodies, more active than any others in most of the phaenomena of nature and art, could not fail to modify the whole theory of che- mistry. The ancient doctrines were revised; new modifications of them were formed by some philosophers ; whilst others discarded entirely all the former hypotheses, and endea- voured to establish new generalizations.
The idea of a peculiar principle of mflam- mability was so firmly established in the
40 INTRODUCTION.
chemical schools, that even the knowledge of the composition of the atmosphere for a long while was not supposed to interfere with it ; and the part of the atmosphere which is absorbed by- bodies in burning, was conceived to owe its powers to its attraction for phlogiston.
All the modern chemists who made experi- ments upon combustion, found that bodies in- creased in weight by burning, and that there was no loss of ponderable matter. It was ne- cessary therefore to suppose, contrary to the ideas of Stahl, that phlogiston was not emitted in combustion, but that it remained in the in- flammable body after absorbing gaseous mat- ter from the air. But what is phlogiston was a question constantly agitated. Inflammable air had been obtained during; the dissolution of cer- tain metals, and during the distillation of a num- ber of combustible bodies. This light and sub- tile matter, therefore, was fixed upon as the prin- ciple of inflammability ; and Cavendish, Kirwan, Priestley, and Fontana, were the illustrious advocates of this very ingenious hypothesis.
In 1774, Bayen* shewed that mercury con- veirted into a calx or earth, by the absorption of air, could be revived without the addition of * Journal de Physique, 1774, page 28S,
INTRODUCTION. 4I
any inflammable substance ; and hence he con- cluded, that there was no necessity for sup- posing the existence of any peculiar principle of inflammability, in accounting for the calcin- ation of metals. The subject, nearly about the same time, was taken up by Lavoisier, who had been for some time engaged in repeating the ex- periments of the British philosophers. Bayen formed no opinion respecting the nature of the air produced from the calx of mercury. Lavoi- sier, in 1775, shewed that it was an air which supported flame and respiration better than com- mon air, which he afterwards named oxygene ; the same substance that Priestley and Scheele had procured from other metallic substances the year before, and had particularly described.*
Lavoisier discovered that the same air is pro- duced during the revivification of metallic calces by charcoal, as that which is emitted during the calcination of limestone; hence he concluded, that this clastic fluid is composed of oxygene and charcoal; and from his expe- riments on nitrous acid and oil of vitriol, he
* In the Journal de Physique for l/^P, Preliminary Dis- course, De la Meiherie has given an adrnir<ible \ieworihe progress of the investigations concerning the gases. See p. 24, &c.
42 INTRODUCTION.
concluded that this gas entered into the compo- sition of these substances.
Dr. Black had demonstrated by a series of beautiful experiments, that when gases are con- densed, or when fluids are converted into solids, heat is produced. In combustion gaseous mat- ter usually assumes the solid or the fluid form. Oxygene gas, said Lavoisier, seems to be compound of the matter of heat, and a basis. In the act of burning, this basis is united to the combustible body, and the heat is evolved. There is no necessity, said this acute philoso- pher, to suppose any phlogiston, any pecu- liar principle of inflammability ; for all the phaenomena may be accounted for without this imaginary existence.
Lavoisier must be regarded as one of the most sagacious of the chemical philosophers of the last century ; indeed, except Cavendish, there is no other inquirer who can be compared to him for precision of logic, extent of view, and sagacity of induction. His discoveries were few, but he reasoned with extraordinary correctness upon the labours of others. He introduced weight and measure, and strict accuracy of manipulation into all chemical processes. His mind was unbiassed by pre-
INTRODUCTION* 43
judice ; his combinations were of the most phi- losophical nature : and in his investigations upon ponderable substances, he has entered the true path of experiment with cautious steps, following just analogies, and measuring hypo- theses by their simple relations to facts.
The doctrine of Lavoisier, soon after it was framed, received some important confirmations from the two grand discoveries of Mr. Caven- dish, respecting the composition of water, and nitric acid ; and the elaborate and beautiful in- vestigations of Berthollet respecting the nature of ammonia; in which phacnomena, before ano- malous, were shewn to depend upon combina- tions of aeriform matter.
The notion of phlogiston, was however de- fended for nearly 20 years, by some philoso- phers in Germany, Sweden, Britain, and Ire- land. Mr. Cavendish, in 17 84, drew a parallel between the hypothesis, that all inflammable bo- dies contain inflammable air, and the doctrine in which they are considered as simple substances, in a paper equally remarkable for the precision of the views displayed in it, and for the accu- racy and minuteness of the experiments it con- tains. To this great man, the assumption of M. Lavoisier, of the matter of heat, appeared
44
INTRODUCTION,
more hypothetical than that of a principle of inflammability. He states, that the phaenomena may be explained on either doctrine ; but he prefers the earlier view, as accounting, in a happier manner, for some of the operations of nature.
De Morveau, Berlhollet, and Fourcroy, in France, and William Higgins and Dr.Hope,in Britain, were the first advocates for the anti- phlogistic chemistry. Sooner or later, that doc- trine which is an expression of facts,must prevail over that which is an expression of opinion. The most important part of the theory of Lavoisier was merely an arrangement of the facts relating to the combinations of oxygene: the principle of reasoning which the French school professed to adopt was, that every body which was not yet decompounded, should be considered as simple ; and though mistakes were made with respect to the results of experiments on the nature of bodies, yet this logical and truly phi- losophical principle was not violated ; and the systematic manner in which it was en- forced, was of the greatest use in promoting the progress of the science.
Till 17 86, there had been no attempt to reform the nomenclature of chemistry ; the
INTRODUCTION.
45
names applied by discoverers to the substances which they made known, were still employed. Some of these names, which originated amongst the alchymists, were of the most barbarous kind ; few of them were sufficiently definite or precise, and most of them were founded upon loose analogies, or upon false theoretical views.
It was felt by many philosophers, particu- larly by the illustrious Bergman, that an im- provement in chemical nomenclature was ne- cessary, and in 1787, Messrs. Lavoisier, Mor- veau, Berthollet, and Fourcroy, presented to the world a plan for an almost entire change in the denomination of chemical substances, founded upon the idea of calling simple bodies by some names characteristic of their most striking qualities, and of naming compound bodies from the elements which composed them.
The new nomenclature was speedily adopted in France ; under some modifications it was received in Germany ; and after much discus- sion and opposition, it became the language of a new and rising generation of chemists in England. It materially assisted the diffusion of the antiphlogistic doctrine, and even facilitated
46
INTRODUCTION.
the general acquisition of the science ; and many of its details were contrived with much address, and were worthy oF its celebrated au- thors: but a very slight reference to the phi- losophical principles of language will evince that its foundations were imperfect, and that the plan adopted was not calculated for a pro- gressive branch of knowledge.
Simplicity and precision ought to be the characteristics of a scientific nomenclature : words should signify things, or the analogies of things, and not opinions. If all the elements were certainly known, the principle adopted by Lavoisier would have possessed an admirable application ; but a substance in one age sup- posed to be simple, in another is proved to be compound ; and vice versa. A theoretical nomenclature is liable to continued alterations; oxygenated muriatic acid is as improper a name as dephlogisticated marine acid. Every school believes itself in the right ; and if every school assumes to itself the liberty of altering the names of chemical substances, in conse- quence of new ideas of their composition, or decomposition, there can be no permanency in the language of the science, it must always be confused and uncertain. Bodies which are
INTRODUCTION. 47
similar to each other should always be classed together ; and there is a presumption that their composition is analogous. Metals, earths, al- kalies, are appropriate names for the bodies they represent, and independant of all specu- lative views ; whereas oxides, suiphurets, and muriates, are terms founded upon opinions of the composition of bodies, some of which have been already found erroneous. The least dan- gerous mode of giving a systematic form to a language, seems to be, to signify the analogies of substances by some common sign affixed to the beginning or the termination of the word. Thus, as the metals have been distinguished by a termination in um, as aurum, so their calci- form or oxidated state, might have been denot- ed by a termination in a, as aura ; and no pro- gress, however great, in the science, could ren- der it necessary that such a mode of appellation should be changed. Moreover, the principle of a composite nomenclature must always be very limited. It is scarcely possible to repre- sent bodies consisting of five or six elements in this way, and yet it is in such difficult cases that a name implying a chemical truth would be most useful.
The new doctrines of chemistry, before 1795,
4t
INTRODUCTION.
were embraced by almost all the active expe- rimental enquirers in Europe ; and the adoption of a precise mode of reasoning, and more re- fined forms of experiment, led not only to the discovery of new substances, but likewise to a more accurate acquaintance with the properties
and composition of bodies that had long been known.
New investigations were instituted with re- spect to all the productions of nature, and the immense variety of substances in the mineral, vegetable, and animal kingdom, submitted to chemical experiments.
The analysis of mineral bodies first at- tempted by Pott in experiments principally on their igneous fusion, and afterwards refined by the application of acid and alkaline menstrua, by Margraaf, Bergman, Bayen, and Achard, received still greater improvements from the labours of Klaproth, Vauquelin, and Hatchett. Hoffman, in the beginning of the 1 8th century, pointed out magnesia as a peculiar substance.* Margraaf, about fifty years later,f distinguished accurately betweea the silicious, calcareous, and
* Hoffman, Opera, Tom. iv. pag. 47.9. t Opuscules, Tom. ii. pag. 137.
INTRODUCTION. 49
aluminous earths, Scheele, in 1774, discovered barytes. Klaproth,* in 1 788, made known zir- cone. Dr. Hope,f strontites in 791» Qadolin, ittriajin 1794; and Vauquelin, glucine in I798.
Seven metals only had been accurately known to the ancieats, gold, silver, mercury, copper, tin, and iron. Zinc, bismuth, arsenic, and anti- mony, though mentioned by the Greek and Roman authors, yet were employed only in certain combinations, and the production of them in the form of reguli or pure metals, was owing to the Alchemists.
Cobalt had been used to tinge glass ia Saxony in the sixteenth century ; but the me- tal was unknown till the time of Brandt, and this celebrated Swedish chemist discovered it in 17 33' Nickel j| was procured by Cronstedt in 1751. The properties of manganese, which was announced as a peculiar metal by Kaim ^ in 1 7 70, were minutely investigated by Scheele and Bergman a few years after. Molybdic acid was discovered by Scheele in 177 8, and a metal procured from it by Hielm in 1782, the same
* Annales de Chiraie, Tom. i. pag. 183. + Edinburgh Trans. Vol. iv. p. 44. X Crell's Annals, 1796. H Bergman Opuscula, Tpin. ii. page 22c I De Metallis dubiis, p. 48. VOL. I. ^
so
INTRODUCTION.
year that tellurium was made known by Muller. Scheele discovered tungstic acid in 17 Si; and soon after a metal was extracted from it by Messrs. D' Elhuyars. Klaproth discovered uranium in 1 7 89,* The first description of the properties of the oxide of titanium was given by Gregor in 1791-+ Vauquelin made known chromium in 1797 ;$ Hatchett columbium in 1801;§ and skortly after, the same substance was noticed by Ekeberg, and named by him tantalium. Cerium was discovered in I804, by Hissinger and Berzelius. Platina had been brought into Europe and examined by Lewis in 1749* and in I803, Descotils, Fourcroy, and Vauquelin announced a new metallic substance in it ; but the complete investigation of the pro- perties of this extraordinary body was reserved for Messrs. Tennant and WoUaston, who in 1 803 and 1804 discovered in it no less than four new metallic substances, besides the body which exists in it in the largest proportion, namely, iridium, osmium, palladium, and rhodium.
The attempts made to analyse vegetable lubstances previous to 17^0, merely produced
* Jntirnal de Physique, 17S9. pag. 39. t Aniiales de ('himie, xii. pag. 147. I Ibid, xxv. 21. Phil. Trans. i8u2.
I
INTRODUCTION. 51
their resolution into the supposed elements of the chemists of those days, namely, salts, Earths, phlegm, and sulphur. Boerhaave and Newmann attempted an examination by fluid menstrua, which was pursued with some success by Rou- elle, Macquer and Lewis. Scheele, between 17 70 and 17.80, pointed out several new vegetable acids. Fourcroy, Vauquelin, Deyeux, Seguin, Proust, Jacquin, and Hermbstadt, between 17 80 and 1790, in various interesting series of expe- riments, distinguished between different secon- dary elements of vegetable matter, particu- larly extract, tannin, gums, and resinous sub- stances ; and investigations of this kind have been pursued with great success by Hatchett, Pearson, Shraeder, Chenevix,Gehlen,Thomson, Thenard, Chevreul, Kind, Brande, Bostock^ and Duncan. The chemistry of animal sub- stances has received great elucidations from several of the same enquirers ; and Berzelius has examined most of their results, and has added several new ones, in a comprehensive work expressly devoted to the subject, pub- lished in 1S08.
That solid masses fell from above, connected with the appearance of meteors, had been advanced as early as 500 years before the
Eg
52 INTRODUCTION.
Christian aera, by Anaxagoras ; and the same idea had been brought forward in a vague manner by other enquirers amongst the Greeks and Romans, and was revived in modern times ; but till 1802 it was regarded by the greater number of philosophers as a mere vulgar error, when Mr. Howard, by an accurate examina- tion of the testimonies connected with events of this kind, and by a minute analysis of the substances said to have fallen in different parts of the globe, proved the authenticity of the circumstance, and shewed that these meteoric productions differed from any substances be- longing to our earth ; and since that period a number of these phscnomena have occurred, and have been minutely recorded.
The philosophy of heat, the foundations of which were laid between 1757 and 11 $5, by Black, Wilcke, Crawford, Irvine, and Lavoisier, since that period has received some new and very important additions, from the inquiries of Pictet, Rumford, Herschel, Leslie, Dalton, and Gay Lussac. The circurosfances under which bodies absorb and communicate heat, have been minutely investigated ; and the important discoveries of the different physical and chemical powers of the difterent solar
INTRODUCTION. 5S
rays; and of a property analogous to polarity in light, bear immediate relation to the most refined doctrines of corpuscular science, and promise to connect^ by close analogies, the chemical and mechanical laws of matter.
A general view of the philosophy of che- mistry was published under the name of Chemi- cal Statics, in 1 803, by the celebrated Berthollet. It is a work remarkable for the new views that it contains on the doctrines of attraction ; views which are still objects of discussion, and which bear an immediate relation to some of the con- clusions depending upon very recent disco- veries.
At the time when the antiphlogistic theory was established, electricity had little or no re- lation to chemistry. The grand results of Franklin, respecting the cause of lightning, had led many philosophers to conjecture, that certain chemical changes in the atmosphere, might be connected with electrical phseno- mena; — and electrical discharges had been employed by Cavendish, Priestley, and Van- marum, for decomposing and igniting bodies ; but it was not till the era of the wonderful discovery of Volta, in i860, of a new electrical apparatus, that any great progress was made in
54
INTRODUCTION.
chemical investigation by means of electrical coHibinations.
Nothing tends so much to the advancement of knowledge as the application of a new in- strument. The native intellectual powers of men in different times, are not so much the causes of the different success of their labours, as the peculiar nature of the means and artificial resources in their possession. Independent of vessels of glass, there could have been no accu- rate manipulations in common chemistry : the air pump, was necessary for the investigation of the properties of gaseous matter ; and without the Voltaic apparatus, there was no possibility of examining the relations of electrical pola- rities to chemical attractions.
By researches, the commencement of which is owing to Messrs. Nicholson and Carlisle, in 1800, which were continued by Cruickshank, Henry, Wollaston, Children, Pepys, Pfaff, Desormes, Biot, Thenard, Hissinger, and Berzelius, it appeared that various compound bodies were capable of decomposition by electricity; and ex- periments, which it was my good fortune to in- stitute, proved that several substances which had never been separated into any other forms of matter in the common processes of experiment,
INTRODUCTION. 53
were susceptible of analysis by electrical power'4 ; in consequence of these circumstances, the fixed alkalies and several of the earths have been shewn to be metals combined with oxy- gene ; various new agents have been furnished to chemistry, and many novel results obtained by their application, which at the same time that they have strengthened some of the doctrines of the school of Lavoisier, have overturned others, and have proved that the generalizations of the Antiphlogistic philosophers were far from hav- ing anticipated the whole progress of discovery.
Certain bodies which attract each other che- mically, and combine when their particles have freedom of motion, when brought into con- tact, still preserving their aggregation, exhibit what may be called electrical polarities ; and by certain combinations these polarities may be highly exalted ; and in this case they become subservient to chemical decompositions ; and by means of electrical arrangements the con- stituent parts of bodies are separated in an uni- form order, and in definite proportions.
Bodies combine with a force, which in many cases is correspondent to their power of exhibit- ing electrical polarity by contact ; and heat, or heat and light, are produced in proportion to the
56
iNTftODUGTlON.
energy of their combination. Vivid inflam- mation occurs in a number of cases in which gaseous matier is not fixed; and this phseno- menon happens in various instances without the interierence of. free or combined oxygene.
Experiments made by Richter and Morveau had shewn that, when there is an interchange of elements between two neutral salts, there is never an excess of acid or basis ; and tlie same law seems to apply generally lo double de- compositions. When one body combines with another in more than one proportion, the se- cond proportion appears to be some multiple or divisor of the first ; and this circumstance, ob- served and ingeniously illustrated by Mr. Dal- ton, led him to adopt the atomic hypothesis of chemical changes, which had been ably defended by Mr. Higgins in 1789, namely, that the che- mical elements consist of certain indestructible particles which unite one and one, or one and two, or in some definite numbers.
Whether matter consists of indivisible cor- puscles, or physical points endowed with attraction and repulsion, still the same conclu- sions may be formed concerning the powers by which they act, and the quantities in which they combine ; and the powers seem capable of
INTRODUCTION. 57
being measured by their electrical relations, and the quantities on which they act of being ex- pressed by numbers.
In combination certain bodies form regular solids; and all the varieties of crystalline ag- gregrates have been resolved by the genius of Haiiy into a few primary forms. The laws of crystallization, of definite proportions, and of the electrical polarities of bodies, seem to be intimately related; and the complete illustra- tion of their connection, probably will constitute the mature age of chemistry.
To dwell more minutely upon the particular merits of the chemical philosophers of the pre- sent age, will be a grateful labour for some future historian of chemistry ; but for a contemporary writer, it would be indelicate to assume the right of arbitrator, even where praise only can be bestowed. The just fame of those who have enlightened the science by new and accurate experiments, cannot fail to be universally ac- knowledged; and concerning the publication of novel facts there can be but one judgment ; for facts are independent of fashion, taste, and caprice, and are subject to no code of cri- ticism ; they are more useful perhaps even when they contradict, than when they support
58
INTRODUCTION.
received doctrines, for our theories are only im- perfect approximations to the real knowledge of things ; and in physical research, doubt is usually of excellent elFect, for it is a principal motive for new labours, and tends continually to the developement of truth.
The slight sketch that has been given of the progress of chemistry, has necessarily been limited to the philosophical details of discovery. To point out in historical order the manner in which the truths of the science have been applied to the arts of life, or the benefits derived by society from them, would occupy many volumes. From the first discovery of the production of metals from rude ores, to the knowledge of the bleaching liquor, chemistry has been continually subservient to cultivation and improvement. In the manufacture of porce- lain and glass, in the arts of dying and tanning, it has added to the elegancies, refinement, and comforts of life ; in its application to medicine it has removed the most formidable of diseases ; and in leading to the discovery of gunpowder, it has changed the institutions of society, and rendered war more independent of brutal strength, less personal, and less barbarous.
It is indeed a double source of interest in
INTRODUCTION.
59
this science, that whilst it is connected with the grand operations of nature, it is likewise subservient to the common processes as well as the most refined arts of life. New laws cannot be discovered in it, without increasing our ad- miration of the beauty and order of the sys- tem of the universe; and no new substances can be made known which are not sooner or later subservient to some purpose of utility.
When the great progress made in chemistry within the last few years is considered, and the number of able labourers who are at present actively employed in cultivating the science, it is impossible not to augur well concerning its rapid advancement and future applications. The most important truths belonging to it are capable of extremely simple numerical ex- pressions, which may be acquired with facility by students ; and the apparatus for pursuing original researches is daily improved, the use of it i^endered more easy, and the acquisition less expensive.
Complexity almost always belongs to the early epochs of every science; and the grandest results are usually obtained by the most simple means, A great part of the phaenomena of chemistry may be already submitted to calcu-
60
INTRODUCTION.
lation ; and there is great reason to believe, that at no very distant period the whole science will be capable of elucidation by mathematical principles. The relations of the common me- tals to the bases of the alkalies and earths, and the gradations of resemblance between the bases of the earths and acids, point out as pro- bable a similarity in the constitution of all in- flammable bodies : and there are not wantin<r experiments, which render their possible de- composition far from a chimerical idea. It is contrary to the usual order of things, that events so harmonious as those of the system of the earth, should depend on such diversiied agents, as are supposed to exist in our artificial arrangements; and there is reason to antici- pate a great reduction in the number of the undecompounded bodies, and to expect that the analogies of nature will be found con- formable to the refined operations of art. The more the phaenomena of the universe are stu- died, the more distinct their connection appears, the more simple their causes, the more magni- ficent their design, and the more wonderful the wisdom and power of their Author.
ELEMENTS
OF
CHEMICAL PHILOSOPHY.
PART I.
ON THE LAWS OF CHEMICAL CHANGES
ON
UNDECOMPOUNDED BODIES
AND
THEIR PRIMARY COMBINATIONS.
ELEMENTS, 8fc.
DIVISION I.
ON THE POWERS AND PROPERTIES OF MAT- TER, AND THE GENERAL LAWS OF CHEMICAL CHANGES.
I. Preliminary Observations.
1. 1. H E forms and appearances of the beings and substances of the external world are almost infinitely various, and they are in a state of continued alteration : the whole surface of the earth even undergoes modifications : acted on by 'moisture and air, it affords the food of plants ; an immense number of vegetable pro- ductions arise from apparently the same mate- rials ; these become the substance of animals ; one species of animal matter is converted into another ; the most perfect and beautiful of the forms of organised life ultimately decay, and are resolved into inorganic aggregates; and the same elementary substances, differently
[ 64 ]
arranged, are contained in the inert soil, or bloom and emit fragrance in the flower, or be- come in animals the active organs of mind and intelligence. In artificial operations changes of the same order occur; substances having the cha- racters of earths are converted into metals ; clays and sands are united so as to become porcelain ; earths and alkalies are combined into glass ; acrid and corrosive matters are formed from tasteless substances ; — colours are fixed upon stuffs, or changed, or made to disappear; and the productions of the mineral, vegetable, and animal kingdoms are converted into new forms, and made subservient to the purposes of civil- ized life.
2. To trace in detail these diversified and complicated phsenomena, to arrange them and deduce general laws from their analogies, would be a labour to which even the longest life of the most industrious and sagacious individual might be devoted in vain. The student who has the advantage of referring to the knowledge accu- mulated by many individuals in different times, may adopt much more simple methods of acquir- ing the science. Those of recurring to its general principles, so as to ascertain the powers and properties of matter, which are the causes of the phaenomena of Chemistry; and of apply- ing these principles to the actions taking place
[ 65 ]
be<^ween tbe various substances existing in nature, or produced by art ; proceeding gradu- ally referring to ob<;ervations, experiments, and distinct analogies, from the more simple to the more complicated changes, so as to understand the laws by which they are governed.
11. Of the Forms of Matter,
1. In the general views that may be taken of the properties of natural substances, certain relations appear, which afford the means of arranging them in four distinct classes, each of which is distinguished by certain sensible and obvious qualities,
2. The first class consists of solids ^ which compose the great known part of the globe. Solid bodies, when in small masses, retain what- ever mechanical form is given to them : their parts are separated with difficulty, and cannot readily be made to unite after separation ; some solid bodies yield to pressure, and do not reco- ver their former figure, when the compressing force is removed, and they are called non-elas- tic solids ; others that regain this form, are called elastic bodies. Solids differ in degrees of hard- ness, in colour, in degrees of opacity or trans- parency, in density or in the weight afforded by equal volumes ; and when their forms are regu- lar or crystallized, in the nature of these forms.
VOL. I. F
[66]
3. The second class consists o£ fluids, of whicK there are much fewer varieties. Fluids when in small mrsses assume the spherical form ; theix parts possess freedom of motion ; they differ in degrees of density and tenacity, in colour and degrees of opacity or transparency. They are usually regarded as incompressible, at least a very great mechanical force is required to make them occupy a space perceptibly smaller.
4- Elastic fluids or gasses the third class exist free in the atmosphere ; but they may be confined by solids, or by solids and fluids, and their properties examined. Their parts are highly move;able ; they are compressible and expansible, and their volumes are inversely as the weights compressing them. All known elastic fluids are transparent, and present only two or three varieties of colour ; they differ materially in density.
5. Besides these forms of matter which are easily submitted to experiment, and the parts of which may be considered as in a state of ap- parent rest, there are other forms of matter which are known to us only in their states of motion when acting upon our organs of sense, or upon other matter, and which are not suscep- tible of being confined. They have been some- times called etherial substances^ which appears a, more unexceptionable name than imponderable
[67l
substances. It cannot be doubted that there is matter in motion in space, between the sun and th^ stars and our globe, though it is a subject of discussion whether successions of particles be emitted from these heavenly bodies, or motions communicated by them, to particles in their vi- cinity, and transmitted by successive, impulses to other particles. Etherial matter differs either in its nature or in its affections by motion ; for it produces different effects; for instance, as radiant heat, and as different kinds of light.
6. The various forms of matter, and the changes of these forms, depend upon active powers, such as gravitation, cohesion, calorific repulsion or heat, chemical attraction, and elec- trical attraction, the laws of which it is neces- sary to study with attention.
III. Kjrravitation.
1. When a stone is thrown into the atmo- sphere it rapidly descends towards the surface of the earth. This is owing io gravitation. All the great bodies in the universe are urged to» wards each other by a similar force. A cannon ball sent from a piece of artillery describes a curve, and at last falls to the ground ; were the impulse given to it by the gunpowder, increased to a certain extent, and exerted in free space, it would continuously revolve round the earth, in
[ 68 1
consequence of the equilibrium between the two forces. The moon and the planets as Newton has demonstrated, are retained in their orbits by simiiar laws, and their harmonious and con- stant revolutions produced.
2. Bodies mutually gravitate towards each other; but the smaller body proportionally more than the larger one : hence the power of gravity is said to be directly as the mass; it is in fact the measure of the mass or quantity of matter.
3- Gravitation acts inversely, as the square of the distance.
IV. Cohesion.
1. When two particles of quicksilver are brought into apparent contact they may be made to unite and form one globule : when a glass tube, having a very JSne bore, is intro- duced into a vessel containing water, the water rises in the tube to a higher level than it occu- pied in the vessel : both these effects are said to be owing to cohesion or cohesive attraction. It is the same force which preserves the forms of solids, and gives globularity to fluids, and is thus a prime cause of the permanency of the arrangements which compose the surface of the globe. It is usually said to act only at the sur- faces of bodies, or by their immediate contact ; but this does not seem to be the case. It
[ 69 ]
certainly acts with much greater energy at small distances ; but the spherical form of minute portions of fluid matter can only be produced by the attractions of all the parts of which they are composed, for each other ; and most of these attractions must be exerted at sensible distances, so that for any thing we know to the contrary, gravitation and cohesion may be mere modifi- cations of the same general power of attraction, in the one case acting at distances that can be easily measured, and in the other case operat- ing at distances which it is difficult to estimate.
2. Some philosophers have attempted to ac- count for attraction in general by supposing that there is a certain unknown matter always mov- ing through the universe in right lines, by which bodies are impelled towards each other ; but though the phasnomena may be explained by such a supposition, it is without proof; and there is no ground for supposing that matter cannot act at a distance, and it is absolutely necessary for the explanation of the planetary motions, to suppose space in the universe yoid of matter.
V. Of Heat, or calorific Repulsion.
1. When a body which occasions the sen- sation of heat on our oro;ans, is brou2:ht into contact with another body which has no suck
[ 70 ]
effect, the result of their mutual action is that the hot body contracts, and loses to a certain extent its power of communicating heat, and the other body expands, and in a degree ac- quires this power.
This law may be exemplified with respect to every form of ponderable matter. If a polished cylinder of tin, which accurately fits a ring, be heated so as to make water boil, it will no lonser pass through the ring, and will be found en- larged in all its dimensions. If spirits of wine be heated in a glass vessel having a narrow tubulated neck, as it becomes capable of com- municating the sensation of heat, it will be found to expand and to rise in the narrow neck ; and if the body of the same vessel be filled with air, and it be inverted in water, its neck containing water, the air will rapidly ex- pand, on the application of a heated body, and will cause the water to descend in the neck of the vessel.*
2. Different solids and fluids expand very differently when heated by the same means.
Glass is less expansible than any of the metals ; 100,000 parts raised from the degree of freezing to that of boiling water, expand so as to become 100,083 parts ; 100,000 of plati- nurai under similar circumstances expand so as * Plate I. fig. 1.
t 71 ]
to become 100,087 ; and equal parts oF gold, antimony, cast-iron, steel, iron, bismutli, cop- per, cast-brass, silver, tin, lead-zinc, and ham- inered zinc expand in the following order : 100094, 100108, 1001 tl, 100112, 100126, 100139, 100170, 100189, 100238, 100287, 100296, 100308. The expansive power of liquids in general is greater than that of solids ; alcohol appears to be more expansible than oils, and oils in general more expansible than water. 100,000 parts of mercury of the same degree of heat as ice become at the degree of heat at which water boils 101,835. All the elastic fluids, or the different species of air that have been examined, as has been demonstrated by Messrs. Dalton and Gay Lussac, expand alike when heated to the same degree; 100 parts of each at the freezing point of water be- coming about 137j5 at the boiling point.
It is evident that the density of bodies must be diminished by expansion ; and in the case of fluids and gasses, the parts of which are mobile, many important phenomena depend upon this circumstance. If heat be applied to fluids or to gasses, the heated parts change their places and rise ; and the colder parts descend and occupy their places. Currents are constantly produced in the ocean and in great bodies of water, in consequence of this ellect.
[72]
The heated water rises to the surface in the tropical climates, and flows towards coldt r ones, thus the warmth of the Gulf stream is felt a thousand miles from its source ; and de^p cur- rents pass from the colder to the warmer parts of the sea: and the general tendency of these changes is to equalize the tetuperature of the globe.
In the atmosphere, heated air is constantly- rising, and colder air rushes in to supply its place ; and this event is the principal cause of winds : the air that flows from the poles towards tlie equator, in consequence of the rotation of the earth, has less motion than the atmos- phere into which it passes, and occasions an easterly current ; the air passing from the equator towards the poles having more motion, occasions a westerly current ; and by these changes, the different parts of the atmosphere are mixed together : cold is subdued by heat, moist air from the sea is mixed with dry air from the land, and the great mass of elastic fluid surrounding the globe, preserved in a state fitted for the purposes of vegetable and animal life.
S. There are very few exceptions to the law of the expansion of bodies, at the time they become capable of communicating the sensation of heat ; and these excepiions seem entirely to depend
[ 73 ]
upon some chemical change in the constitution of bodies, or on their crystalline arrangements. Thus clay contracts considerably in dimensions by a very intense heat, and on the measure of its contractions the pyrometer of Wedgwood is founded : but in this case the clay first gives ofF water, which was united to its parts, and afterwards these parts cohere together with more force, and from being in a state of loose aggregation become strongly united. Water expands a little before it congeals, and expands considerably during its conversion into ice ; but in this case it assumes the crystalline form ; and its parts whilst they are arranging them- selves to form regular solids, probably leave greater interstices than they occupied when at uniform distances in the fluid. Thus the same weight of matter will occupy much more space when arranged in a certain number of octahe- drons, than when arranged in a similar number of cubes, or hexagonal prisms. Certain saline solutions likewise that shoot into prismatic crystals, expand at the moment they become solid ; and the case is the same with cast-iron, bismuth, and antimony.
The expansion of water during its conversion into ice, is shewn by the circumstance of ice swimming upon water ; and if water in a deep vessel be examined at the time ice is forming, it
[ u 3
ivill he found a little warmer at the bottom than at the top ; and these circumstances are of great importance in the ioeconomy of nature. Water congeals only at the surface, where it is liable to be acted upon hy the sun, and by warm currents of air which tend to restore ittd the fluid state; and when water approaches near the point of freezing it begins to descend^ so that no ice can form till the whole of the water has been cooled to the point where it possesses the greatest density ; and in the deep parts of the sea and lakes, even in some of the northern latitudes, the duration of the long winter is insufficient to cool the water to the degree at which ice forms.
4. When equal quantities of the same matter differently heated are mixed together, as much as the one contracts, so much the other seems to expand. It is easy to prove this by shaking together 100 parts of mercury so hot as not to be touched without pain, and 100 parts in its common state, having previously measured the space they occupy ; if the mixture is made in the tube that contained the hot mercury, there will be no sensible change of volume.
It is on the idea, that when heat or the power of repulsion is communicated from body to body, as much is gained by one body as is lost by the other, that thermometers have
been framed, and the doctrines of temperature^ and Capacity for heat founded,
5. The most common thermometer is a glass bulb, containing mercury, terminated by a glass tube, having a very narrow bore. The mer- cury is boiled to expel any air or moisture that might be attached to it ; and at the moment it is in ebullition, the extremity of the tube being drawn to a fine point, is hermetically sealed by a spirit lamp. For the purpose o£ acquiring a scale, the bulb is first plunged into melting ice, and the place where the mercury stands is marked ; the bulb is afterwards plunged into boiling water and the same ope- ration repeated. On Fahrenheit's scale this space is divided into 180 equal parts, and simi- lar parts are taken above and below for extend- ing the scale, and the freezing point of water is placed at S2**, and the boiling point at 212°. 1.8 degrees of Fahrenheit are equal to one de- gree of the centigrade thermometer, and 2.25 to one degree of Reaumur.
Other fluids besides mercury, such as alcohol, are sometimes used in thermometers, particu- larly for measuring low degrees when mercury freezes.
Air is employed in the differential thermo- meter, which consists of two bulbs filled with air, and connected by a capillary tube contain-
[ 76 ]
ing oil of vitriol ; the heated body is brought in contact with one bulb, the air of which expands and drives the fluid towards the other bulb.*
6. Temperature is the power bodies possess of communicating or receiving heat, or the energy of repulsion ; and the temperature of a body is said to be high or low with respect to another, in proportion as it occasions an expansion or contraction of its parts ; and the therraometer is the common measure of temperature.
7. When equal volumes of different bodies of different temperatures are suffered to remain in contact till they are possessed of the same tem- perature, it is found that this temperature is not a mean one, as it would be in the case of equal volumes of the same body. Thus, if a pint of quicksilver at 100°, be mixed with a pint of water at 50°, the resulting temperature is not 75°, but about 70° : the mercury has lost 30**, whereas the water has gained only 20°. In the common language of chemical philoso* phers this difference is said to depend upon the different capacities of bodies for heat, and the capacity of a body is said to be greater or
• Plate 1. fig. 2, represents Mr. Leslie's differential thermo- meter. Fig. 3 is copied from Van Helmont. This instrument appears to have been the first in which the expansive power of heated air, was exhibited by its action upon cold air.
[ 11 1
less, in proportion as its temperature is less or more raised by the addition, or diminished by the subtraction of equal quantities of the power of repulsion, or heat. Thus mercury is said to have a much less capacity for heat than water ; and taking the facts above stated as data, and comparing the weights of the two bodies, which are as I3.3 to 1, their capacities will be to each other as about I9 to 1.
Tables of the relative capacities of bodies are given in the works of different authors. In re- ferring to the various bodies which are the subjects of chemistry, this property will be de- scribed amongst other properties. ' In general it appears that the substances most expansible by heat are those which have the greatest capa- cities ; thus gasses in general have greater capacities than fluids, and fluids than solids; but the exact ratio has not been yet deter- mined.
8. Different bodies, it appears, have their temperatures differently raised by the addition, or diminished by the subtraction of equal quantities of heat, or the power of repulsion, and they are likewise affected by heat, or ex- panded with very different degrees of celerity. If slender cyhnders of silver, of glass, and of charcoal, of equal length and size, be held in the central part of the flame of a candle, tLe
[ 78 }
silver rapidly becomes heated throughout, and cannot be held in the hand; the heat is more slowly communicated through the glass, but the charcoal becomes red-hot at the one extre- mity long before any heat is felt at the other extremity. These differences are said to de- pend upon the different pov*^ers of these bodies for conducting heat; thus the silver is said to be a better conductor than the glass, and the glass than the charcoal. In general those bodies that are the densest, and that have the least capacity for heat, are the best conductors ; thus the metals conduct better than any other solids ; gasses are worse conductors than fluids, and fluids than solids: but there are exceptions with respect to this correspondence between conducting power and density, and a remarka- ble one, in the densest known body in nature, platlna, which is perhaps the worst conductor amongst the metals.
Animal and vegetable substances in general, are very bad conductors ; thus the hair and wool of animals, and the feathers of birds, are admirably fitted to protect them from the cold, and they inclose and retain air, which being a still worse conductor, enhances the effect. It was supposed by Count Rumford, that fluids and gasses are perfect nonconductors of heat, and that their particles can be heated in no other
[ 79 ]
way, except by coming in succession to the source of heat ; but some very conchisive ex- periments seem to render this opinion untena- ble. In general, however, fluids and gasses alter their places, from a change of specific gravity much more rapidly than they communi- cate or receive heat. This is iUostrated by a very simple experiment; let an air thermometer be inverted in a vessel of wAter, so that the ex- tremity of the bulb is barely beneath the surface, let a little ether be poured upon the water so as to form a stratum about -f- of an inch above the thermometer, and let the ether be in- flamed ;* however delicate the thermometer, the ^ir in it will not soon expand ; the ether boils violently, but a very long process of this kind is required to communicate any sensible heat to the water. Unless the particles of gasses and fluids had been capable of communicating heat to a certain extent, the upper strata of liquids would be almost the only permanently heated parts ; and heat would be constantly accumu- lating on the surface of extensive seas. Our lower atmosphere likewise would be intensely cold during the absence of the sun ; but by the relations between the conducting power and the mobility of fluids and gasses ; the changes offem- perature of air and water are made progressive « See Plate I. fig. 4.
[ 80 ]
and equable, and adapted to a habitable globe. As heat is propagated very slowly through gaseous bodies, so they communicate it very slowly to other bodies, a circumstance that might be expected from the small quantity of matter they contain, when compared to other substances. The heat of metals at the tempera- ture of 120° is scarcely supportable; water scalds at 150°; but air may be heated to 240° without being painful to our organs of sen- sation, and a temperature near this was expe- rienced for some minutes, by Sir Joseph Banks, Sir Charles Blagden, and Dr. Fordyce, in a room artificially heated.
The power of abstracting heat in air is like- wise comparatively very small ; in the high northern latitudes a cold has been experienced without injury, in which mercury froze ; and if in this state of the atmosphere, metallic sub- stances, of the same temperature, were touched, a sensation like that of burning was experienced, and the part blistered.
9. Heat, or the power of repulsion, may be considered as the antagonist power to the attrac- tion of cohesion, the one tending to separate, the other to unite the parts of bodies ; and the forms of bodies depend upon their respective agencies. In solids the attractive force pre- dominates over the repulsive ; in fluids, and in
[ «1 1
elastic fluids they may be regarded as in dif- ferent states of equilibrium ; and in ethereal substances the repulsive must be considered as predominating over, and destroying the attrac- tive force.
All the different substances in nature, under certain circumstances, are probably capable of assuming all these forms ; thus solids, by a cer- tain increase of temperature, become fluids, and fluids gasses; and rice versa, by a diminution of temperature gasses become fluids, and fluids solids;
Instances of the fusion of solids by heat are too familiar to require any particular notice ; when water becomes steam by boiling, it is merely the conversion of a fluid into an elastic fluid ; and a simple instance of this circumstance may be given in the ebullition of ether. Let a little ether be introduced into a small glass retort filled with water, and inverted in water ; the ether will swim above the water, in the upper part of the retort; let a heated bar of metal* be held near the part of the retort containing the ether, as the heat is communicated, globules will be seen to rise, and in a very short time elastic fluid will be formed, in such quantities, as to expel the water from the vessel; on suf-
Plate I. fig. 5.
VOL. I. G
[ 82 1
ferirsg the glass to cool, the elastic matter will be condensed, and will become again Huid.
If a globule of mercury be held in a spoon oF platina, over the flame of a lamp, it wiil be vividly agitated, and will rapidly diniinish. This is owing to its becoming elastic, and flying off in gas; and by a very low temperature, which may be artificially produced by mixing together very cold snow and a salt called muri- ate of lime, mercury may be congealed into the solid form.
JDifFerent bodies change their states at very diETerent temperatures. Thus mercury, which is a solid at about 40 below Fahrenheit, boils at about 66O ; sulphur, which becomes fluid at 218% boils at 570°; ether boils at 9'S°. The temperatures at which the common metals be- come gaseous, are generally very high, and most of them incapable of being produced by common means. Iron, manganese, platina, and some other metals, which can scarcely be fused in the best furnaces, are readily melted by electricity; and by the Voltaic apparatus a degree of heat is attained, in which platina not only fuses with readiness, but seems even to evaporate:
With respect to the conversion of solids, fiiiids, or gasses, into ethereal substances, the;
[ 83 ]
proofs are hot of the same distinct nature as those belonging to their conversion into each other. When the temperature of a body is raised to a certain extent, it becomes lumin- ous ; and heated bodies not only affect other bodies by direct contact, but likewise exert an influence on them at a distance, which is as- cribed to what is usually called radiant heat. One solution of this phenomenon is, that par- ticles are thrown off from heated bodies with great velocity, which by acting on our organs produce the sensations of heat or light, and that their motion, communicated to the particles of other bodies, has the power of expanding them ; thus if heat, or the force of repulsion, be so increased in an elastic fluid, as to over- come the force of cohesion and gravitation, these particles would move in right lines through free space ; and we know of no other effects they could produce, than those of heat and light. It is perhaps in favour of this opinion, that all the different elastic fluids expand equally, when their temperatures are equally raised; and from observations made on the eclipses of Jupiter's satellites, and from other phenomena presented by the heavenly bodies, it appears that the motions of light are equable. It may, however, be said, that the radiant
mafters emitted by bodies in ignition, are spe- cific substances, and that common matter is not susceptible of assuming; this form; or ii may- be contended, that the phenomena of racli.iiion do, in fact, depend upon motions communicated to subtile matter every where existing in space.
9. The temperatures at which boflies change their states from fluids to solids, though in general definite, are influenced by a few cir- cumstances, such as mrtion and psessure. Water, kept perfectly at rest, may sometimes be cooled to 22° without cone;e!aii!>n : hut if at a temperatute below 52°, it be agitated, ice in- stantly forms, A saturated solution of Gl .uber's salt, introduced whilst warm into a boltle. frc m which the pressure of tlse atmosphere is ex- cluded, remains liquid after cooling, but if the atmc sphere be suffered to act upon it, it in- stantly crystallizes. The boiling point of fluids is still less fixed, than-the point of fusion of solids, and is immediately dependent upon pressure. Thus ether will boil readily at the freezing point of water, in the exhausted re- ceiver of an air pump ; and it appears from the researches of Professor Robison, that in a vacuum, all liquids boil about bwer, than, in the open air. Under pressure, liquids may- be heated to.a high degree ; water in a Papin's
C 85 3
digester, may have its temperature raised to S'OO', but at the moment the pressure is removed, elastic matter is disengap^ed with great violence.
10. A peculiar distinction has been made by some autliors between permanent eiaslic Ouids, and elastic fluids which are conderisi- ble by pressure or cold ; but these substances differ only in the degree of the point of va:;or-» ization ; and steam at 5Qu decrees of Faiiren- heit, there is every reason to beh'eve, would be equaliy incondensibie with air at a range of temperature such as we can commimd btlow our common temperatures; and some gassts that are permanent under all common circum- stances, as ammonia, are condensible by intense cold aided by pressure.
Ali bodies that boil at moderate temperatures, seem to evaporate, so as to produce a certain quantity of elastic matter in the common state of the atmosphere ; and this quantity is greater in proportion as the temperature is high. Ac- cording to Mr. Dalton, the force of vapour in- creases in geometrical progression to the tem- perature, but thiE ratio differs in different fluids. It is certain that as the temperature approaches near the point of ebullition, in liquids, the strength of the vapour, i. e. the quantity that would rise in free space, rapidly increases.
In h©t, dry weather, it is obvious that tliere
[ 86 3
must be much more vapour in the atmosphere, than in cold wet weather; and the largest quantity exists in summer and in the tropical climates, when moisture is most needed for the purposes of life ; and it appears to be the aqueous vapour in the atmosphere, which, when condensed by the mixture of cold with hot air, or by other agencies occasioning a change of its temperature, is the cause of dew, mists, rain, and ultimately of springs, and rivers.
11. When solids are converted into fluids, or fluids into gasses, there is always a loss of heat, of temperature, and vice versa, when gasses are converted into fluids, or fluids into solids, there is an increase of heat of temperature, and in this case it is said that latent heat is ab- sorbed or given out. Thus if equal weights of snow at and of water at 172° be mixed to- gether, the whole of the snow is melted, but the temperature of the mixture is found to be 32°} so that 140" degrees of heat are lost. Again, if water be heated in a Papin's digester to 300 degrees, and the valve be raised, a quantity of steam instantly rises, which has the temperature of 212°, and the temperature of the water in the digester is found to be the same, so that a great quantity of heat of temperature is lost in eonvertino; the water into steam.
[S7J
% when the'air is at 20", a quantity of water Wexposed to it in a tall glass, the water gra- dually cooh down to 22°, without freezina;, but if it be shaken, So as to be converted into ice, the temperatuie of the ice is found to be at 32° so that the degree of heat is raised during the act offreezlns.
If one part of steam or aqueous gas, at 212°, be mixed with 6 parts by \veig;ht of water at 62°, the whole of the steam will be condensed, and the temperature of the fluid will be about 512°, so that there is an immense increase of the heat of temperature, and 900° degrees may be considered as taken from the steam, and as added to the water.
All the phenomena of these changes may be referred to a simple general law, of which Dr, Black was the discoverer, and which has been most ably illustrated by the researches of Wilke, Watt, Irvine, and Crawford, namely, " that whenever a body changes its form, its relations to temperature are likewise changed, either increased or diminished;" and many im- portant operations, both artificial and naturalj depend upon this law. The knowledge of it, for instance, led Mr. Watt to make his great improvement ot* the steam engine, by which the steam is condensed out of the cylinder in which
[ 8g
its forceis efficient, and fresh gaseous matter intro- duced vvithoutany chance of a loss of its elasticity.
One of the most perfect modes of heating large rooms, and of procuring a uniform tempe- rature for the purposes of manufacture, is by the condensation of steam. By the cold pro- duced in consequence of the evaporation of water in hot climates, congelation is effected ; and in the nights in Bengal, when the tempe- rature is not below fifty, by the exposure of water in earthenware pans upon moistened bamboos, thin calces of ice are formed, which are heaped together and preserved under ground by being kept in contact with bad conductors of heat. The cold produced by evaporation, is likewise the cause of the formation of ice in Mr. Leslie's elegant experiment, in which sul- phuric acid is placed in a vessel upon the plate of an air-pump, and water in another vessel raised above it ; the surfaces both of the acid and the water being considerable. When an exhaustion is made, the sulphuric acid rapidly absorbs the vapour rising from the water; fresh vapour is immediately formed, and in a few minutes, if the circumstances are favour- able, spicule of ice are seen to form on the surface of the water.
When aqueous vapour is condensed into
[ 89 ]
fluid in tTie atmosphere, heat is produced ; and the for mat ion of rain, hail, and snow, tends to miti^^ate the severity of the winter. In the sum- mer, evaporation is constantly tending to cool the surface. The melting of the polar ice moder- ates the heat that would arise in the northern regions from the constant presence of the sun during the polar summer. And the evolution of heat during the congelation of water, prevents too great a degree of cold, and renders the transitions of temperature more slow and gradual.
- 12. When the forms of bodies are changed by mechanical means, or when mechanical forces are made to act upon them, there is usually a change of temperature. A piece of caotchouc extended and suffered to contract rapidly by mechanical means, becomes hot ; a nail is easily made red hot by a few wdl di- rected blows of the hammer ; and by the friction of solids, considerable increase of temperature is produced ; thus the axle trees of carriages sometimes inflame.
By strong pressure, fluids even are made lu- minouSj as has been lately shewn by M. Des- saignes.
When an elastic fluid is compressed by me- chanical means, its temperature is raised, and when the compressing forces are great and
t 9^ J
I'apidiy applied the effect is such as to cause the ignition of bodies. A machine for setting fire to tinder of the agaric, by the compression of air, has been for some time in use.
When air is made to expand by removing compressing forces, a diminution of tempera- ture is occasioned. Thus the mercury in the thermometer sinks at the time of the rarefac- tion of air, by exhausting the receiver of an air pump.
In the common language of chemistry, it may be said that the capacity of elastic fluids for heat is diminished by compression, and en- creased by rarefaction ; and it is probable that when the volumes of elastic fluids are changed by change of temperature, there is likewise a change of capacity, and on these ideas, it is easy to account for the correspondence between the diminution of the temperature of the atmos- phere and its height ; for if it be conceived that the capacity of air rarefied by heat, in- creases as it ascends, the heat of temperature which was the cause of its ascent, must, at a certain elevation, become heat of capacity : and the higher and more rarefied the air, the more it is removed from the source of heat, and the greater its power of diminishing tempera- ture.
A very curious phenomenon is produced
t 91 1
during the action of the fountain of Hiero at Schemnitz in Hungary ; the air in the machine is compressed by a cohnnn oF water, 260 feet high, and when a stop-cock is opened so as to suffer air to escape, its sudden rarefaction produces a degree of cold which not only precipitates aqueous vapour, but causes it to congeal in a shower of snow, and the pipe from which the air issues, becomes covered with icicles. Dr. Darwin has ingeniously explained the production of snow on the tops of the high- est mountains by the precipitation of vapour from the rarefied air which ascends from plains and valiies The Andes, placed almost under the line, rises in the midst of burning sands ; about the middle height is a pleasant and mild cli- mate; the summits are covered with unchang- ing snows .* and these ranges of temperature are always distinct ; the hot winds from be- low, if they ascend, become cooled in con- sequence of expansion, and the cold air, if by any force of the blast, it is driven down- wards, is condensed, and rendered warmer as it descends.
It seems probable that the capacity of solids and fluids is increased by expansion, and di» minished by condensation, and if this is the case, the additions of equal quantities of heat will give smaller increments of temperature at
I 92 ]
h'lgh than at low degrees, which must to a cer* tain extent render the thermometer inaccurate in the higher degrees, though prohably only to a very small extent, of little importance as to all practical purposes ; and this cause of inac- curacy appears to be counteracted by another^ that fluids seem to be more expansible by heat in proportion as their temperature is higher.
13. In all chemical changes there is an alter- ation of temperature; and inmost instances when gasses become fluids, or fluids solids, there is an increase of temperature ; and vice versa, there is usually a diminution of tem- perature when solids become fluids, or fluids, solids. For instance, when the highly inflam- mable substance called phosphorus, the pro- perties of which will be hereafter described, is burnt in the air, it is found to condense a parti- cular part of the air, and a high temperature is produced during the process. When a solid amalgam of bismuth, and a solid amalgam of lead, substances which will be noticed in that part of this work relating to the metallic com- pounds, are mixed together, they become fluid, and the thermometer sinks during the time of their action.
There are, however, a number of cases in which, though gaseous bodies or fluids are formed from solids, an increase of temperature
[93],
occurs : thus, in the explosion of gunpowder a large quantity of aeriform matter is disengaged, yet a violent heat is produced.
And there is an instance in which at the time of the separation of two species of gaseous matter from each other, which is connected with expansion, there is an increase of temper- ature; thus, when a little of the gas whicli I have named Euchlorine, and which consists of the substance called by the French chemists oxyrauriatic gas, and oxygene gas, is gently heated in a small glass tube over mercury, an explosion takes place, fire appears, and yet the two gasses occupy a greater volume than before the explosion.
14. As attempts have been made to account for attraction, by the supposition of the exist- ence of a peculiar matter, so calorific repulsion has been accounted for by supposing a subiile fluid, capable of combining v/ith bodies, and of separating their parts from each other, which has been named the mailer of heat, or caloric.
Many of the phenomena admit of a happy explanation on this idea, such as the cold pro* duced during the conversion of solids into fluids or gassesj and the increase of temperature connected with the condensation of gasses and fluids ,• but there are other facts which are not so easily reconciled to the opinion .- such are the
[ 94 ]
production of heat by friction and percussion ;- and some of the chemical changes which have been just referred to. When the temperature of bodies are raised by friction, there seems to be no diminution of their capacities, using the word in its common sense ; and in many che- mical changes connected with an increase of temperature, there appears to be likewise an increase of capacity. A piece of iron made red hot by hammering cannot be strongly heated a second time by the same means, unless it. has been previously introduced into a fire. This fact has been explained by supposing that the fluid of heat has been pressed out of it, by the percussion, which is recovered in the fire ; but this is a very rude mechanical idea : the ar- rangements of its parts are altered by hammer- ing in this way, and it is rendered brittle. By a moderate degree of friction, as it would appear from Rumford's experiments, the same piece of metal may be kept hot for any length of time ; so that if heat be pressed out, the quantity must be inexhaustible. When any body is cooled it occupies a smaller volume than before: it is. evident, therefore, that its parts must have ap- proached towards each other : when the body is expanded by heat, it is equally evident that its parts must have separated from each oihen The immediate cause of the phsenomena of heat
I 95 1
then is motion, and the laws of its communica- tion are precisely the same as the laws of the communication of motion.
Since all matter may be made to fill a smaller volume by cooling, it is evident that the parti- cles of matter must have space between them ; and since every body can communicate the power of expansion to a body of a lower tem- perature, that is, can give an expansive motion to its particles, it is a probable inference that its own particles are possessed of motion ; bat as there is no change in the position of its parts as long as its temperature is uniform, the mo- tion, if it exist, must be a vibratory or undulatory motion, or a motion of the particles round their axes, or a motion of particles round each other.
It seems possible to account for all the phas- nomena of heat, if it be supposed that in solids the particles are in a constant state of vibra- tory motion, the particles of the hottest bodies moving with the greatest velocity and through the greatest space ; that in fluids and elastic fluids, besides the vibratory motion, which must be conceived greatest in the last, the particles have a motion round their own axes, with diffe- rent velocities, the particles of elastic fluids mov- ing with the greatest quickness; and that in etherial substances the particles move round their own axes, and separate from each other^
[ 96 ]
penetrating in right lines through space. Tem- perature maybe conceived to depend upon the Velocities of the vibrations ; increase of capacity on the motion being performed in greater space ; and the diminution of temperature daring the conversion of solids into fluids or o;asses, may be explained on the idea of the loss of vibra- tory motion, in consequence of the revolution of particles round their axes, at the moment when the body becomes fluid or triform, or from the loss of rapidity of vibration in conse- quence of the motion of the particles through greater space
If a specific fluid of heat be admitted, it must be supposed liable to most of the affections which the particles of common matter are as- sumed to possess, to account for the phaeno- inena; such as losing its motion when combining with bodies, producing motion when trans- mitted from one body to another, andgaining projectile motion, when passing into free space: so that many hypotheses must be adopted to account for its mode of agency, which renders this view of the subject less simple than the other. Very delicate experiments have been made which shew that bodies when heated do not increase in weight. This, as far as it goes, is an evidence against a specific subtile elastic fluid producing the calorific expansion ; but it
4
[9?]
cannot be considered as decisive, on account of the imperfection of our instruments ; a cubical inch of inflammable air requires a good balance to ascertain that it has any sensible weight, and a substance bearing the same relation to this, that this bears to platinum, could not perhaps be weighed by any methods in our possession.
Some arguments have been raised in favour of the existence of a specific fluid of heat, from the circumstances of the communication of heat to bodies in exhausted receivers, and from the manner in which they are affected by this heat; but there are no means known in experimental science of producing a perfect vacuum ; even the best Torricellian vacuum must contain elas- tic matter. The great capacity of such highly rarefied matter is an obstacle to the indication of temperature ; but supposing a communication of heat, the laws must be analogous to those of heat communicated to common air. If a long cylinder of metal, placed perpendicularly, be heated in the middle, the warmest part will be above, from the ascent of heated particles of the elastic medium ; but if a sphere be heated in the middle, the hottest portion will be below, as the heated elastic matter must remain lono-er in contact with the inferior than with the supe- rior portion.
The laws of the communication of heat, and VOL. I. H,
[ 98 ]
the philosophy of its effects, are independent of this speculative question, which will again be considered, under new relations, in the part of this work relating to the properties ethereal or radiant matter.
IV. On chemical Attraction^ and the Laws of Combination and Decomposition.
i. When olive oil and water are adtated to- gether they refuse to act upon each other, and separate according to the order of their densi- ties, the oil swimming above the water. Oil and water will not mix intimately ; they will noi combine; and they are said to have no che- mical attraction or ajfLnitf for each other. But if oil and soap lees, or solution of potassa in water, be mixed, the oil and the solution blend together, and a species of soap will be formed, which maybe procured as a soft solid substance by evaporating a part of the water. This is an instance of combination ; and solution of potassa and oil are said to attract each other chemically, or to have an affinity for each other.
2 Oil is almost insipid, but the solution of potassa is a caustic substance, which corrodes the skin, and has a strong taste. — The body resulting from their union differs both from the oil and the alkali in taste, smell, colour, and in all its sensible qualities ; and it is a general
C 99 ]
GhsxRcter oi" chemical combination, that it chano-es the sensible qualities of bodies.
Corrosive and pungent substances often be- come mild and tasteless by their union, as is the case with sulphuric acid and quicklime, which form gypsum, or sulphate of lime.
Bodies possessed of little taste or smell often gain these qualities in a high degree by combi- nation. Thus sulphur, when inflamed ia oxy- gene or in common air, dissolves and forms an elastic fluid of a most penetrating and disagree- able odour and peculiar flavour. The forms of bodies, or their densities, likewise usually alter ; solids become fluids, and solids and fluids gasses, and gasses are often converted into fluids or solids. Thus sugar, or salt, or isinglass, dis solves in water. The consumption of charcoal in our fires depends upon its uniting with a part of the air, with which it forms an invisible elastic fluid : mercury is rendered solid by being heated with half its weight of tin, and a substance of this kind is used for silvering mirrors. The gas produced by the combustion of charcoal is con- densed by another gas procured from quicklime and sal ammoniac, when they are mixed over mercury ; and the two invisible elastic fluids form a white saline solid,
3. Many substances may be made to unite by chemical affinity or attraction : thus common , H2
f ]
salt, sugar, and pearl-ashes, will all dissolve together in water. And the fosilalkali, sand and the glass of lead, when melted toge- ther, unite to form flint glass And in like manner, porcelain is formed by heating together mixtures of different earths. In a number of the productions of nature likewise many sub- Stances are combined into one mass or com- pound. Thus many stones and gems are capable of being resolved into several elements ; and in the vegetable and animal kingdom there are scarcely any compounds which do not contain more than two principles, and complexity of constitution seems uniformly connected with organization.
4. That chemical attraction may be exerted between bodies, it is necessary that they should be brought into apparent contact. Thus no body will act chemically upon another at any sensible distance.
5. A freedom of motion in the parts of bodies, or a want of cohesion, greatly assists combina- tion ; and this circumstance is so marked, that it was formerly considered as a chemical axiom, which is still retained in some elementary books, that bodies cannot act chemically on each other unless one of tiiem be fluid or seriform. Such an extensive general zation is, however, incqr- regt ; thus crystalline munate of lime and snow.
0
C 101 ]
both cooled to 0° Fahrenheit act upon each other ijnd liquify; and crystals ofoxalic acid and dry lime treated in the same manner readily com-* bine. The hardest arid the densest bodies, however, vmdergo chemical chanties Avith the greatest difficulty. Thus the sapphire in its crystallized state, is not affected by boiling sul- phuric acid ; but when in a fine pov/der, as alu* mine, it is easily dissolved Minute division, or solution, or fusion is necessary in almost all chemical processes. In the chemical arts these circumstances are always attended to ; and in the phcenomena of external nature, the com- mencement of chemical operations may in almost all cases be traced to the agencies of fluids or aeiif'orm substances. Thus in the bosom of our rocks and mountains, where aic and water are incapable of penetrating, all is permanent and still, without change or motion; wherever wa- ter and air are capable of acting, decomposition slowly goes on ; and these agents gradually change the nature of the surface, render liie soil fertile, and decompose and degrade the exterior of strata.
5. If equal weights of magnesia and of quick- lime, in fine powder, and diluted aquaforiis or nitric acid, be mixed together and suff red to remain for some hours, it will be found by a mi- nute examination, that a considerable part oi the
[102]
lime has been dissolved, but all the masnesia will remain untouched. Hence, it is said, that lime has a stronger altraclion for nitric acid, than magnesia has.
This is proved likewise, by another experi- ment of a different kind : it is easy to make a solution of magnesia, in nitric acid, by heating them together; and to make a solution of lime in water, by agitating some powdered quick- lime in distilled water. Let tlie solution of lime be poured into the solution of magnesia, a white powder or precipitate will separate, and gradually fall to the bottom of the vessel in which the mixture is made. This powder, when examined, is found to be magnesia, and, it is said, that magnesia is precipitated from siitric acid, in consequence of the stronger attraction of lime for that acid.
Ail bodies, that differ in their nature, com- bine with different degrees of force ; and some very important chemical phacnoraenain the arts depend upon this circumstance. Thus the astrin- gent 01 tanning substance, in the bark of trees, which is soluble in water, is attracted from water, by the prepared skins of animals, in con- sequence of their stronger affinity Tor it, and the skin, from being destructible by boiling water, and decomposable, becomes indestruc- tible and permanent. In like manner, indigo,
t ^03 ]
and other dyeing materials, are separated from their soluiions, by vegetable or animal fibres, and new combinations of ihem effected; and a number of instances of the same kind mio-ht be brought forward.
6. Different bodies unite with different de- grees of force ; and hence, one body is capable of separating others, from certain of their com- binations ; and inconsequence of the same cir- cumstance, mutual decomposilions of different compounds take place. This has been called double ajjinily^ or complex chemical attraction. Thus, if an aqueous neutral solution of lime and nitric acid, and a like solution of magnesia and sulphuric acid, be mixed together, the lime wiil quit the nitric acid, to unite to the sulphuric acid, and the magnesia will leave the sulphuric acid, to combine with the nitric acid. The combination of nitric acid and magnesia, will remain in solution; but the compound of lime and sulphuric acid, being only slightly soluble in water, will for the most part be pre- cipitated, in the form of a white powder.
In many cases decompositions, that cannot be produced by single attractions, may be produced by double affinities. Thus the elements of sulphate of baryta, or the c(»m- bination of sulphuric acid, and the earth called baryta, are so firmly united, that
[ 104 ]
no alkali, nor earth, will separate the acid from the baryta. Potassa, which has a very strong attraction for the acid, will not decompose it alone ; but if potassa, combined with carbonic acid, be digested for some time, with powdered sulphate of baryta, there is a double decompo- sition; and combinations of sulphuric acid and potassa, and carbonic acid and baryta, are formed.
7. If one part of pure oxygene gas, and two parts of pure hydrogene gas, in volume, be mixed together, in a glass tube, over mercury, furnished with wires for passing the electrical spark through it, and they be inflamed by the electrical spark;* the gaseous matter will dis- appear, and water will result. If two parts of oxygene, be employed, and two of hydrogene, one part of oxygene will remain ; in whatever proportions they are mixed together, it is found, that one of oxygene always condenses two of hydrogene. It is evident then, that oxygene and hydrogene, combine only in defin- ite proportions, and that the water resulting is always the same in its constitution.
If ^ piece of well burnt charcoal be introduced into a vessel, two thirds filled with oxvo;ene gas, over mercury; and the mercury be brought to the same level on the inside and on the * See Plate I. fig. 6.
[ 105 ]
outside of the jar, and the charcoal be inflamed by a burning glass ;* there will be at first, ^n expansion, but after the experiment is over, it will be found, that the volume of the gas has not perceptibly altered; and if the charcoal has beeij in sufficient quantity, the whole of the oxvp'ene will be found converted into carbonic acid ; now the densities of oxygene gas and carbonic acid gas, in whatever way they are formed, are always the same ; and to each other, as 34 to 47 nearly. It is evident then, that carbonic acid must always contain the same weight of oxygene and charcoal. If there is twice as much oxygene in the vessel, as is ne- cessary for the consumption of the charcoal, half of it remains untouched ; and if the char- coal is partly unconsumed, still the gas is the same in quality; it always contains by weight, 5.7 of charcoal and 15 of oxygene.
There is an inflammable gas, called carbonic oxide, which burns with a blue flame, and which is obtained by igniting together zinc filings and chalk. When two in volume of this gas, and one in volume of oxygene, are acted upon by an electric spark, over mercury, they inflame, and there result exactly two volumes of car- bonic acid gas ; there is no other product, and the weight of the carbonic acid gas, exactly * Plate II. fig. /.
[ 106 ]
equals the weight of the carbonic oxide and the oxygene gas; so it is evident, that the carbo- nic oxide contains exactly half as much oxygene as carbonic acid, that is 5-7 of charcoal, require 7.5 of oxygene, to become carbonic oxide. Again this is proved by decomposition : if elec- trical sparks be passed through carbonic acid gas, over mercury, it expands, and part of it is decomposed, two volumes becoming two vo- lumes of carbonic oxide, and one volume of oxygene.
When the saltj called nitrate of ammonia, is decomposed by heat, an elastic fluid is disen- gaged, called nitrous oxide ; when one volume of this gas, is mixed with one volume of hydro- gene, and an electric spark is passed through the mixture, inflammation takes place, water is formed, and one volume of elastic matter remains, which is azote. Now as one volume of hvdro- gene takes half a volume of oxygene, lor its conversion into water, it is evident, that this gas, nitrous oxide, must be composed of two in volume of azote, and one in volume of oxy- gene, condensed into a space equal to two»
There is a gas produced by the solution of copper in diluted nitric acid. If a little of this gas be passed into a curved glass tube* over mercury, and metallic arsenic be sublimed in * Plate II. fig 8.
[ 107 ]
the gas, it is gradually decomposed. A solid combination of arsenic and oxygene is formed, which is found (if the weight of the azote re- maining be compared with that of the nitrous gas) to contain half a volume of oxygene, and half a volume of gas remains, which is azote. So it is evident, that as azote combined with one proportion of oxygene gas, forms nitrous oxide, so combined with two proportions, it forms nitrous gas ; and one volume of nitrous gas mixed over water with half a volume of oxy- gene, is condensed, and forms a solution of nitrous acid gas in water. So that this body must consists of azote with, four proportions of oxygene, nitrous oxide being considered as azote with one proportion of oxygene ; and the quan- tities in these bodies are always the same
It would be easy to bring forward a great col- lection of evidences to shew, that in all compound gaseous bodies, the quantities of the elements are uniform for each species* and that when two
* That the proportions in compound gases are definite, has long been generally acknowledged, but Mr. Higgins is, I believe, the first person who conceived that when gasses com- bined in more than one proportion, all the proportions of the same element were equal; and he founded this idea, which was made public in 1789, on the corpuscular hypothesis, that bodies combine particle with particle, or one with two, or three, or a greater number of particles. Mr. Dalton, about 1802, adopting a similar hypothesis, apparently without the knowledge of what Mr. Higgins had written, extended his views to compounds in general. Mr. Richter seem* to hav«
[ 108 ]
gaseous elements combine iri more than one pro- portion, that the second or third proportion is always a multiple, or a divisor of the first ; and the case seems to be analogous with respect to all true chemical compounds, whether solids or fluids, in which no mechanical mixtures can be suspected, and where no partial decompositions can have taken place.
Thus if sulphuric acid be poured into any solution of baryta, the solid precipitate of sul- phate of baryta which falls down, is uniform in its nature, and always contains about 34 of acid, and 66 of baryta ; and the case is the same with other similar compounds, and with neutral salts in general.
And if tv»'o neutral salts mutually decompose
been the first person to shew that in the decomposition of neutral salts by double affinity, the neutral state is preserved ; and likewise that, when a metallic salt is decomposed by a metal, all the oxygene and acid is transferred, and the metal only changed, and that the new solution is as neutral, as the former one. It had been ascertained, by different experiments, that in certain cases when solids dissolved in gasses, the volume is unchanged, and some instances of the combination of gasses were kiicuvn, in which the volumes bore simple ratios to each other, as in iiitioits Dxide, and water; but M. Gay Lussac is- the first philosopher who attempted to generalize on the phe- nomena, and shew that in all cases where gasses unite, it is always in simple ratios of volume, 1 to l,or 1 to 2, or 1 to 3, and that the condensation, if any, is in a simple ratio. His very ir-geniou« ideus cn thib .subject, were made known towards the close of liSOS. BerzeUns, in a work publishv d in 1810, has determined ver) coi rci tij , s(/me of ihe definite proportions of several important compounds. See Hi^gins's comparative View.
[ 109 ]
each other, in the interchange of principles, there is never an excess of acid or of basis,* and the resiiUing compounds are likewise per- fectly neutral. Thus if 100 parts of nitrate of baryta, which contain 41 nitric acid, and 59 baryta, be mixed with 67 of sulphat of potassa, which consist of 30 of sulphuric acid, and 37 potassa, there will be found 89 of sulphate of baryta, and 78 of nitrate of potassa ; so that 41 of nitric acid will combine with the 37 of potassa, and 30 of sulphuric acid with the 59 of baryta.
It is evident from these circumstances, that when one body has the power of detaching another from its combinations, it will always detach the same proportion. Thus from what- ever basis baryta attracts sulphuric acid, it will always detach the same quantity; and the same quantity of potassa, from whatever acid it pre- cipitates magnesia, will always throw down the same proportion.
8. In cases when an alkaline substance com- bines with more than one proportion of acid, the same circumstances seem to occur as in
Dalton's new Chemical Fhilosophy. Richter Ueber die neuren gegenstande der Chemie. Memoires d' Arcueil, T. ii. Bcr- zelim Annales de Chemie, T. Ixvii. Thomson's system of Chemis- try^ vol. Hi.
* M, M. Gay Lussac and Thenard, have lately stated, " that in some mutual decorapositions of fluates, and muriates; slightly acid solutions become alkaline; Recherches, T. ii. page 28; but such changes must be complicated; and perhaps a minute investigation may shew that they are not anomalous.
I no ]
the combinations of gaseous bodies. The pro- portion is either a multiple or a divisor of the first ; this is shewn by a very simple experiment, first made by Dr. Wollaston : let a given weight of the salt called carbonate of potassa, be thrown into a tube over mercury, and diluted sulphuric acid suflBcient to cover it be introduced into the tube, a certain volume of carbonic acid gas will be disengaged; let an equal weight of the salt be heated to redness, when it becomes a subcar- bonate, and let this subcarbonate be treated in the same way, it will be found to give off exactly half as much carbonic acid sas.
9. In the combination of solid and fluid sub- stances which have not yet been decompounded, with gasses, and in the union of compound inflammable bodies with each other, and in all mutual decompositions between bodies of this class, similar circumstances appear to occur : thus there are two combinations of mercury with oxygene, the black and the red ; and one appears to contain twice as much oxygene as the other. There are two known combinations of iron with oxygene, the black and the red oxide of iron ; and the oxygene in the first being considered as 2, that in the second must be considered as 3, that is 100 parts of iron take 29 parts of oxy- gene to become the black oxide, and 43.5* to become the red.
* These results I have obtained very nearly, namely, 29
[ 111 ]
The decompositions of compounds containing oxymuriatic gas, or chlorine gas by water, afford the best and most intelligible instances of double decomposition. If equal volumes of light inflam- mable air or hydrogene, and chlorine be mixed together, and exposed to day-light, they slowly act upon each other, no condensation takes place, and they form an equal volume of muriatic acid gas ; so that muriatic acid gas consists of hydro^ gene and chlorine in equal volumes ; and water, as has been before stated, consists of two parts in volume of hydrogene, and one part in volume of oxygene. Now phosphorus and sulphur, and most of the metals, combine with chlorine, and form peculiar compounds, many of which are decomposed by water, and the results are phosphorus, sulphur, or the metals combined with oxygene, and muriatic acid ; and the oxi- dated compounds formed, are the same as those produced in other ways; and it is evident, that the quantity of hydrogene given to the chlorine to form the acid, must be exactly in the ratio of the oxygene added to the inflamma- ble substance or the metal; thus phosphorus burnt in chlorine in excess, forms a white volatile substance, which 1 have named phos- phor anee. When water is added to this, phos-
and 43 ; and they differ very little from those of Mr. Hassen- fraiz, Dr. Thomson, and Mr. Beraelius.
{ 112 ]
phoric and muriatic acids are formed, and there are no other products.
10. As in all well known compounds, the proportions of the elements are in certain de- finite ratios to each other ; it is evident, that these ratios may be expressed by numbers ; and if one number be employed to denote the smallest quantity in which a body combines, all other quantities of the same body will be multiples of this number ; and the smallest proportions in which the undecomposed bodies enter into union being known, the constitution of the compounds they form may be learnt, and the element which unites chemically in the smallest quantity being ex- pressed by unity, all the other elements may be represented by the relations of their quantities to unity.
Hydrogene gas, or inflammable air is the substance of which the smallest weights seem to enter into combination ; and it appears to exist in no definite compound in less pro- portion than water. The specific gravity of hydrogene is to that of oxygene as J 5 to I; and as 2 volumes of hydrogene to 1 of oxygene enter into the composition of water, the raiio of the hydrogene in water will be to tlie oxygene as 2 to 15 ; and it may be regarded as composed of two proportions of hydrogene
[ 113 ]
and one of oxygene : and the number repre- senting hydrogene will be 1, and that repre- senting oxygene 15.
The weights of equal volumes of azote and oxygene are to each other nearly as 13 to 15 ; therefore supposing the number representing the proportion, in which azote combines, gained from the composition of nitrous oxide, which contains two volumes of azote to one of oxy- gene, it will be represented by 26 ; and nitrous oxide will consist of two proportions of azote equal to 26, and one proportion of oxygene, equal to 15. Nitrous gas will consist of 1 of azote and 2 of oxygene, 26 and 30. Nitrous acid gas of I of azote and 4 of oxygene, 26 and 60.
Ammonia, which is decomposed by electri- city into 3 volumes of hydrogene and 1 volume of azote, will consist of 6 proportions of hydro- gene and 1 proportion of azote, or 6 and 26.
The weight of chlorine or oxymuriatic gas^ is to that of hydrogene nearly as 33.5 to 1; and muriatic acid gas consists of equal volumes of these gases, and therefore is composed of 33,5 of chlorine, and 1 of hydrogene ; — but § of chlorine may be made to combine with one of oxygene in volume ; and double proportions of this gas combine to form compounds, which when decomposed by water, alford compounds containing single proportions of oxygene, so that the ratio of chlorine to oxygene, is that of 67
VOL. I. I
[ 114 ]
to 15, and the number representing chlorine is correctly stated 67.
In like manner it is easy to deduce the num- ber representing the other undecompounded bodies ; and they will be found to correspond as nearly as can be expected, in whatever way they are obtained. Thus, whether the number representing the proportion in which potas- sium the basis of potassa combines, be gained from its combination with oxygene or with chlorine, the result will scarcely differ ; for 8 grains of potassium converted into the com- pound of chlorine and potassium I have found gain about 7.1 grains, and when converted into potassa, they gain a grain and and as 7.1:8: : 67 : 75-4 ; and as . 1.6 : 8 : : 15 : 75, giving the number representing potassium as about 75-
It is easy to form a series of proportional numbers by taking of these numbers, on the supposition that water is composed of one pro- portion of hydrogene ahd one of oxygene ; but in this case the number representing the pro- portion in which oxygene combines must con- tain a fraction ; and the calculations are much expedited, and the formula rendered more simple, by considering the smallest proportion an integer.
Mr. Higgins has supposed that water is com- posed of one particle of oxygene and one of hydrogene, and Mr. Dalton, of an atom of each; but in the doctrine of proportions derived from
[ M5 3
facts, it is not necessary to consider the combine* ing bodies, either as composed of indivisible particles, or even as always united, one and one, or one and two, or one and three propor- tions. Cases will hereafter be pointed out, in which the ratios are very different ; and at pre- sent, as we have no means whatever of judging either of the relative numbers, figures, or weights, of those particles of bodies which are not in contact, our numerical expressions ought to relate only to the results of experiments.
If it should hereafter be discovered, that any of those substances now considered as undecom- pounded, consist of other elements, these ele- ments must be represented by some division of their numbers ; and should even hydrogene be found a compounded body, it would merely be necessary to multiply all the numbers repre- senting the other elements, by some common number which would admit of a division into proportions, representing the elements of hy- drogene ; so that no discovery concerning the composition of bodies, can interfere with the general law of the definite nature of their com- binations.
1 1. If the black oxide ofmanganese be exposed to a strong heat, it gives oiBT oxygene gas, and becomes brown ; but no heat as yet applied is ca- pable of depriving it of the whole of its oxygene.
12
I 116 ]
Hence itis evident that when one proportion oF one substance is combined with more than one proportion of another, the first proportions may- be separated with much more facility than the last. There are numbers of other instances ; thus the carbonate of soda, which contains two pro- portions of carbonic acid to one of soda, gives off half its carbonic acid with great facility, by heat, but obstinately retains the other half. Nitric acid is easily brought to the state of nitrous gas by the abstraction of oxygene : nitrous gas with more difficulty is converted into nitrous oxide, but nitrous oxide is still less decomposable than nitrous gas.
When one proportion of a body is combined with two or more proportions of another, it seems to enter with more difficulty into new combinations, than when it is combined with one proportion. Thus iron combined with two proportions of sulphur in golden pyrites is not acted upon by diluted sulphuric acid : but when combined only with one proportion of sulphur, as in the common artificial sulphuret, it is readily acted upon.
It seems from these facts that two or more proportions of one body attract a single pro- portion of another body with more energy than one proportion, and that two proportions or mgre adhere to a single proportion with less
[ "7 ]
energy than one proportion ; or at least that a second or a third proportion adheres with less energy than the first.
It may possibly be said, that the effect of two or three proportions, in defending one propor- tion from the action of a new substance, may depend upon mechanical causes, from their more completely enveloping its parts ; but the other solution of the effect seems to be the most probable.
12. M. BerthoUet, to whom the first distinct views of the relations of the force of attraction to quantity are owing, has endeavoured to prove that these relations are universal, and that elec- tive affinities cannot strictly be said to exist. He considers the powers of bodies to com ine as depending in all cases upon their relative attrac- tions, and upon their acting masses, whatever these may be : and he conceives that in all cases of decomposition, in wliich two bodies act upon a third, that third is divided between them in proportion to their relative affinities, and their quantities of matter. Were this proposition strictly correct, it is evident that there could be scarcely any definite proportions : a salt crys- tallizing in a strong alkaline solution, would be strongly alkaline ; in a weak one less alkaline ; and in an acid solution, it would be acid \ which does not seem to be the case. In combina->.
I
[ 11' ]
tions, in which gaseous bodies are concerned, the particles of which have perfect freedom of motion, the proportions are unchangeable ; and in all solid compounds, which have been accur- ately examined, and in which there is no chance of mechanical mixture, the same law s6ems to hold good. It is certainly possible to dissolve different bodies in fluid menstrua, in very various proportions, but the result may be a mixture of different solutions, rather than a combination. M. Berthollet brings forward glasses and alloys of metals, as compounds, con- taining indefinite proportions ; but it is not easy to prove, that in these, all the eletnents are chemically combined ; and the points of fusion of alkali, glass, and certain metallic oxides, are so near each other, that transparent mixtures
of them may be formed. It cannot but be
supposed, that the attractive power of matter is general, but in the formation of aggregates, cer- tain arrangements seem to be always uniform.
IS- M. Berthollet conceives, that he has prov- ed that a large quantity of a body having a weak affinity, may separate a part of a second body, from a small quantity of a third, for which it has a strong affinity ; but even granting this, it does not destroy the idea of definite proportions. Thus in the fact, noticed by Bergman, the decompo- sition of sulphate of potassa by nitric acid, one
[119]
proportion of potassa may be separated from the acid ; and the other proportion may combine with two proportions of acid ; phaenomena ana- logous to those of common double affinity.
M. Berthollet states, that a large quantity ,of potassa will separate a small quantity of sul- phuric acid from sulphate of baryta ; but he made his experiments in contact with the atmos- phere, in which carbonic acid constantly floats ; and carbonate of potassa and sulphate of baryta, mutually decompose each other (6). Even allowing the correctness of his views, still he has not given a complete statement of facts. If potassa separates sulphuric acid from baryta, either there must exist an insoluble sulphate of baryta, containing more baryta than the com- mon sulphate, and which of course may contain two proportions of baryta ; or baryta, sulphuric acid, and potassa, must all be dissolved, in the same fluid, which seems highly improbable. M. Berthollet regards baryta as separable froiQ sulphuric acid, by potassa ; but has not endea- voured to shew in what form it appears after the process.
14. M. Berthollet states, that soda is capable ef separating a certain quantity of potassa from sulphuric acid ; but, in his experiment, water was present, as the soda must have been a hydrate ; and he likewise used alcohol ; and thephseno-
I
[ 120 ]
menon may be a phaenomenon of double attrac- tion, Potassa has a mucli stronger attraction for water than soda ; and the soda may quit its water, and the potassa its sulphuric acid ; and the effect may be assisted by the stronger at- traction of hydrate of potassa for alcohol.
In general, when large quantities of fluid or fusible bodies, are used in experiments, the attraction of the substances which are capable of acting upon each other, is more readily brought into play. In many solutions all the elements are in chemical combination ; and their separations depend not merely upon the relative attractions of their parts, but likewise on the manner in which they are acted on by water ; and earths, and oxides, are usually thrown down from their solutions in union with water.
15. When an alkali precipitates an earth from its solution in an acid, the earth, accord- ing to M, Berthollet's ideas, ought to fall down in combination with a portion of acid. But if a solution of potassa be poured into a sulphuric solution of magnesia, the precipitate produced, after being well washed, affords no indication of the presence of acid ; and M. Pfaff has shewn by some very decisive experiments, that mag- nesia has no action upon neutral combina- tions of the alkalies and sulphuric acid ; and
[ 131 ]
likewise, that the tartaroiis acid is entirely se- parated from lime, and the oxalic acid from oxide of lead, by quantities of sulphuric acid, merely sufficient to saturate the two bases ; and these are distinct and simple instances of elective attraction. Again, when one metal precipitates another from an acid solution, the body that falls down is usually free both from acid and oxy- gene : thus zinc precipitates lead and tin, and iron, copper ; and the whole of the oxygene and the acid, is transferred from one metal to the other.
16. M. Berthollet, in crystallizing sulphate of potassa, from acid solutions, states that he obtained salts, of which the first portion con- tained 55.83 of acid in 100 parts, and another portion only 49-5 ; but it is far from improba- ble, that these salts were both mixtures of the acidulous sulphate, and the neutral sulphate of potash ; and the idea is strengthened by the circumstance, that he obtained neutral sulphate from the same solution, towards the end of the process ; but even allowing the substances to have been principally simple binary combina- tions, and not mixtures, still the potassa and the acid, may be regarded in them as in definite proportions. The number representing potassa being considered as 90, and that representing" sulphuric acid as 75? the first may be conceived
[ 122 ]
to contain four of alkali and seven of acid, and' the second, three of alkali and four of acid.
In cases in which solutions of salts are formed in acid or alkaline menstrua, which are sup- posed incapable of decomposing them, the re- sults must be considered as depending upon a new combination ; and in the evaporation of the water or of the menstruum, and the crystal' lization of the remaining constituents, the pro»- portions, that have acted, will determine the nature of the solids which are formed. There appears no difficulty in reconciling the doctrine of definite proportions, with the influence of quantity ; none of the experiments of M. Ber- thollet can be considered as strictly contra- dictory to the doctrine, and some of the most important results of this sagacious chemist afford it confirmation.
17. M. Berthollet supposes that the attrac- tions of bodies for each other, are inversely, as the quantities that saturate. Thus, magnesia and ammonia, take up more sulphuric acid than equal quantities of potassa ; and therefore he concludes, that magnesia and ammonia, have a stronger attraction for acids than potassa: yet potassa instantly separates magnesia and am- monia from acids ; and though the facility with which ammonia is expelled from a compound^ may be hypolhetically accounted for, by assum-
[ 123 ]
feig that the ease, with which it takes the gaseouS state, assists its escape ; yet magnesia is in an opposite case i and to account for chemical changes, by supposing the effects of forms of matter, which are about to appear, or powers not in actual existence, such as elasticity or cohe- sion, is merely the solution of one difficulty, by the creation of another ; and ammonia, when, solid or fluid, should require a new force to render it elastic : and the cohesion, in a com- pound, can only be regarded as the exertion of the chemical attractions of its elements. The action between the constituents of a compound must be mutual ; sulphuric acid, there is every reason to believe, has as much attraction for baryta, as baryta for sulphuric acid : and baryta is the alkaline substance, of which the largest quantity is required to saturate sul- phuric acid ; therefore, on M. Berthollet's view, it has the weakest affinity for that acid ; but less sulphuric acid saturates this substance, than any other earthy or alkaline body ; therefore, according to M. Berthollet, sulphuric acid has a stronger affinity for baryta, than for any other substance ; which is contradictory.
18. It cannot be laid down as a general law, that the attractions of bodies are connected with the weights of the proportions in which they combine; yet in some cases the proportions.
[ m ]
which unite in the greatest quantity, or the bodies represented by the highest numbers, are separated by proportions combining in smaller quantity, or by bodies represented by lower numbers. Thus gold, pbtina, mercury, and silver, are separated in their metallic states by the common metals, which are represented by much lower numbers, and the metallic oxides by the alkalies ; but there are many exceptions; and the intensity of attraction seems to be de- pendent upon other causes, which are intimately related to the electrical phaenomena, to be dis- cussed in the next section.
19. The uniformity of the law of condensa- tion, when gasses combine and form denser gaseous compounds, in which the volume is unaltered, or in which one of the elements is condensed to or in which both are condensed to ^, and the regularity of the forms of solid bodies seem to depend entirely upon the con- stancy of the nature of the combination, and probably upon the corpuscular aggregates being all of the same kind. If the particles of matter be supposed to be globular, or to act in spheres of attraction and repulsion, it would be easy to account for their forms, by supposing a few independent primary arrangements. Thus, four particles may compose a tetrahedron, ' five, a tetraedral pyramid, six an octaedron,
C 125 ]
or a triedral prism, and eight, a cube or a rhomboid.
20. It would be premature in this part of the work, to enter upon any more minute views of the laws of attraction, and the more refined details will properly follow the history of the agencies of different bodies on each other.
With respect to a power so constantly in action, it is necessary, however, even at an early period of the study, to possess some definite ideas. If it be regarded as capricious in its effects, and tending constantly to produce different arrangements, chemistry would be without a guide, without certain combinations, and no results of analysis could be perfectly alike; but fortunately for the progress of sci- ence, this is not the case ; the changes of the terrestrial cycle of events, like the arrangements of the heavens, and the system of the planetary motions, are characterized by uniformity and simplicity ; weight and measure can be applied to them, their order perceived, arid their laws discovered.
VII. Of Electrical Attraction mid Repulsion, and their Relations to Chemical Changes.
1. If a piece of dry silk be briskly rubbed against a warm plate of polished flint glass, it will be found to have acquired the property of
[ 126 ]
adhering to it, which it will retain for some seconds ; if at the time this adhesive power exists, the silk and glass be separated from each other, they will both be found to have gained the property of attracting very light substances, such as the ashes of paper or fragments of gold leaf; and the long filaments of the silk, if there be any, will be seen to repel each other.
2. These bodies are said to be electrically excited^ and the phsenomena are called electrical phaenomena ; the peculiar circumstances under which they occur, are best observed by the use of an instrument called the electrical machine ; it consists of a cylinder of glass* supported upon glass pillars, and which can be made to revolve, so as to press against a cushion of silk rubbed over with a little amalgam of zinc and mercury ; and of two cylinders of metal, one in contact with the cushion, and the other op- posite to the glass cylinder, both supported upon glass.
g. If two gilt pith balls, suspended upon strings of silk covered with tinsel, be hung upon a wire, placed in contact with either of the me- tallic cylinders, and the machine be put in action, the balls will repel each other; but if one ball be attached to a wire,, connected with one metallic cylinder, and the other ball be * Plate II. fig. %
[ 1" ]
attached to a wire connected with the other, the two balls, when the machine is put into action, will attract each other ; and at the mo- ment that they come in contact, sparks of light will be perceived, if the experiment be made under favourable circumstances.
As the two balls, when in contact with the same cylinder, may be considered as receiv- ing the same impulse or impression, they are said to be similarly eleclrijied; but -when in contact with different cylinders, they are said to be differently eleclrijied; and electrified bodies that repel each other, are considered as in the same electrical states ; those th?t attract each other as in different electrical states.
4. There are probably no two bodies differ- ing in nature, which are not capable of exhibit- ing electrical phsenomena, either by contact, pressure, or friction ; but the first substances in which the property was observed, were vitreous and resinous bodies ; and hence the different states were called states of resinous and vitreous electricity ; and resinous bodies bear the same relation to flint glass, as silk. The terms, ne^p,' tive and positive electricity, have been likewise fidopted, on the idea, that the phaenomeija de- pend upon a peculiar subtile fluid, which be- comes in excess in the vitreous, and deficient in the resinous bodies; and which is conceived
[ m ]
by its motion and transfer, to produce the elec- trical phaenomena.
5. Flint glass and silk, silk and sulphur, sulphur and metals, resin and metals, all by friction or contact, become strongly electrical, and of course attractive, and communicate their attractive powers to small masses of matter brought in contact with them ; a pith ball, or a slip of gold leaf that has been touched by flint glass, excited by silk, will be repelled by a ball or slip that has been touched by silk excited by sulphur, or by a ball or slip that has been touched by sulphur excited by metals, so that the attractive and repellent slates, depend entirely upon the actions of the two substances, and not upon any power peculiar to, and inhe- rent in each.
6. It is upon this circumstance, that the elec- trometer, which might be called the differeniial one, is framed ; it consists of two gold leaves attached to a metallic plate, and included in a hollow cylinder of glass,* fixed upon another metallic plate, which is connected with two pieces of tin foil, pasted upon the glass oppo- site to the leaves. When any electrified body is made to touch the upper plate, the gold leaves diverge ; if their divergence is increased by the approach of flint glass excited by silk, they are
• Plate II. fig- 10,
[ 129 ]
said to have tlie same state as the glass, the vitreous or the positive ; if their divergence is diminished, they are said to be in the opposite state, or to possess the resirlous or negative electricity.
1. Wheri luminous phaenomena are connected with electrical excitation, the different states may be known by presenting a metallic point to the excited body ; if rays of light Issue from the point to the body, it is said to be negatively electrified : but if the point appears simply luminous, without sending off any rays, the selectricity is said to be positive.
8. For measuring small degrees of electricity of bodies, as compared with those of others of the same kind, the eleclrical balance of Coulomb is applied; it consists of a giJt pith ball, placed upon a metallic rod, on the opposite extremity of which is a thin leaf of metal ; *the rod is suspended horizontally, by a fine metallic wire, which passes into a glass tube, to the top of which it is attached ; the glass tube is inserted into a cylinder of glass, which contains a cop- per ball, connected with a small bar of metal, which is carried through an aperture in the glass cylinder, into the atmosphere; a very small force only is required to twiit the wire, and when the two balls are brought in contact, and the bar touched by the electrified body^
VOL. 1, K
[ 130 ]
thev gain the same kind of electricity, and re- pel each other; and the degree of their repulsion may be measured by a scale of degrees, made on the circumference of the cylinder.*
9. Bodies receive the electrical influence in- different manners. If a rod of glass be brought in contact with any excited electrical body, it will receive the electrical influence in the part where it touched the body, and will be elec- trical, to a little distance, round the point of contact; but its remote parts will not be affected. A rod of metal, on the contrary, suspended on a rod of glass, and brouglit in contact with an electrical surface, instantly becomes electrical throughout. The glass, in common philoso- phical language, is said to be a nonconductor of electricity, or an substance; the metal
a conductor. Some bodies are affected to a much greater extent than glass; but not nearly so much as metals, such are animal and vegetable substances, water, and fluids containing water ; they are said to be imperfect conductors. Ac- cording to the statements of Mr. Cavendish, iron conducts 400 millions of times better than water, sea water 100 times better than distilled water, and water saturated with salt, 720 times better. The mineral acids are the best fluid conducting substances known, and after them, ' * Plate II. fig. 11.
[ 131 ]
saline solutions, the powers of which appear to be nearly in proportion to the quantities oP salts they coniain. Charcoal and metals, and the greater number of inflammable metallic compounds, are onduclors. Alcohol and ether^ are very imperfect conductors ; and sulphur^ oils, resinous substances, metallic oxides and compounds of chlorine, nonconductors.
10. There is a stone found in many parts of the world, called tourmaline, which is sometimes crystallized as a nine-sided prism, terminated by a three-sided and a six-sided pyramid ; when this subbtance is gently heated, it becomes electrical, and one extremity, that terminated by the six- sided pyramid, is positive, the other is negative ; to a certain extent, its electricities are exalted by increasing the temperature ; when it begins to cool, it is sdii found electrical; but the elec- tricities are changed, the pyramid, before posi- tive, is now negative, and vice versa. When the stone is of considerable size, flashes of lig-ht may be seen along its surface.
There are other gems and crystallized sub- stances, which possess a property similar to that of the tourmaline. The luminous appearance of some diamonds, when heated, probably de- pends upon their electrical excitation. The sub- stance called the Boracite, which is a cube, having its edges and angles defective, btcomes
K 2
[ 132 ]
electrical by heat, and in one variety presents no less than eight sides, in different states, four positive, four negative; ;ind the opposite poles are in the direction of the axes of tlie crystal.
11. It would appear, that in all cases of elec- trical action, the two electrical states are always coincident, either in different parts of the same body, or in two bodies ; and that they are always equal, and capable of neutralizing each other. If a connection be made by a wire, between the positive and negative conductors of tlie elec- trical machine, during the time of its action, all electrical effects cease; and to produce a suc- cession of effects, both conductors must be brought near bodies connected with the ground, which gain the opposite slate, in consequence of what may be called induclion, and which will be explained in the next paragraph.
12. When a nonconductor, or imperfect conductor, provided it be a ihin plate of matter, placed upon a conductor, is brought in con- tact, with an excited electrical body; the surface, opposite to that in contact, gains the opposite electricity from that of the excited body ; and if the plate be removed from the conductor and the source of electricity, it is found to possess two surfaces in opposite states. If a conductor be brought into the neighbourhood of an ex- iiited body, the air, which is ^ nonconductor,
[ 133 ]
being between them ; that extremity of the conductor, which is opposite to the excited body, gains the opposite electricity, and the other extremity, if opposite to a body connected with the ground, gains the same electricity, and the middle point is not electrical at all. This is easily proved, by examining the electricity of three sets of gilt pith balls raised on wires on the dilferent parts of the conductor, which is thus affected by induced electricity.
If, instead of air, a plate of mica or glass be between the two conductors, the same phaeno- mena will occur ; so that it would appear that the conductor merely gains two opposite elec- tricities, or polar electricities, of the same kind as those of the nonconductor. The phsenoraena of sparks, of discharges, and of accumulated electricity, depend upon this law. In the case of the common electrical spark, a stratum of air is charged in the same manner as a glass bottle, partially coated with tin foil, is charged in the Leyden experiment ; * when the hand is held near the positive conductor of an electrical machine, the person standing on the ground, the hand is rendered negative, and the states become exalted, till the polarities, as they may l^e called, are annihilated through the air, * Plate II. fig. 12.
[ 134 ]
producing a spark, a snap, and a distinct sensa- tion. If a number of small pith balls, placed upon a surface of metal, are caused to approach an electrified body, they are brought into the opposite state by induction, and are attracted towards the body ; but when they come in contact with it, this state is destroyed, they gain the same state, and are repelled ; and if they are properly placed, their alternate attrac- tions and repulsions may be produced, as long as the machine is in action.
13. If a number of cylinders of metal, iimi' lated on glass, be placed in a line with each other, but not in contact, and the last be con- nected with the ground ;* when a powerfully elec- trified conductor of a machine, is brought op- posite to the first, they will all become electrical, and every insulated cylinder will present two poles ; the negative pole of one being opposite to the positive pole of the other ; and if a spark is produced by means of the last, sparks occur throughout the whole arrangement. In like manner a series of Leyden jars may be made to charge each other, the outer surface of the first renderins; neoiative the inner surface of the second, and so on ; and by connecting the sur- faces, that have the same kind of electricity, in,
* Plate III. fig. 13.
[ 135 ]
the first place, and then connecting two oppo- site surfaces in the series, a powerful explosion* may be produced.
14. When a point connected with the ground, is brought near an electrified substance, it rapidly gains the opposite state, and an imme- diate discharge takes place, which continues till the equilibrium is restored. Large surfaces are electrified by induction much more slowly than small ones, and are capable of accumulat- ing much more electricity ; which renders the discharge from them much more violent. In- deed the electrical powers seem entirely to belong to the surfaces of bodies, and not to be connected with the quantity of solid matter they contain.
15. It is in consequence of the principle of induction, that the condensing electrometer is so much more sensible than the common electro- meter ; this instrument consists of two plates of polished metal,-f the surfaces of which are parallel, one connected with the plate of the electrometer, the other moveable, in connexion with the ground, and the plates are very near each other. When the body supposed to be electrical, is made to touch the top of the electro- meter, and is afterwards removedj in separating the plates, the effect will be perceived.
* Plate in. fig. 14. t Plate III. fig. 15.
[ 136 ]
16. The difference in what are called the conducting powers of bodies, seems to de- pend entirely upon the different manner in which they receive the electrical polarities, or in which their parts become capable of com- municating attractive or repellent powers, to other matter. Nonconductors appear to receive polarities, only with great diSicultyj but retain them for a long while, and present probably a number of different alternations of poles, within a small space, and cannot be effected to any great distance. Imperfect conductors receive polarity with more facility, but present fewer alternations, and piieserve their electricities for a shorter time. Perfect conductors are easily affected throughout ; but present at most only two poles, and the powers rapidly destroy each other. The diflScuIty with which nonconduc- tors receive polarity, is shewn in the phaeno. mena of charging thick and thin coated plates of glass and mica. The thin plates are capable of being charged much more highly than the thick ones, and the accumulation on the oppo- site surfaces is much greater.
Rarefied air or gaseous matter, is much more susceptible of receiving polarities, than dense air or gaseous matter ; and hence, the electrical spark will pass much further through rarefied air or light gasses, than through dense air or
[ 137 3
heavy gasses ; it passes much further likewise in gasses J than in nonconducting fluids.
17. If a nonconducting surface, coated with two conducting surfaces, and charged so as to give a spark of an inch in length, through air, be connected by both its conducting surfaces, with a similar apparatus not charged ; then both systems piay be discharged together; but the spark they will give, will be only half as long as the single one would have given, if discharged alone. The quantity of the electricity in this Cc^se, is conceived not to be altered, but its intensity, is said, to be only half as great when it is discharged fron^ a double siirface ; and these expressions of intensity and quantity, though it is not easy to attach any very definite ideas to them, are nevertheless useful, in giving more facility to the arrangement of some important electrical phsenomena.
18. When very small conducting surfacesare used for conveying very large quantities of'elec- tricity, they become ignited ; and of the different conductors that have been compared, charcoal is most easily heated by electrical discharges,* next iron, platina, gold, then copper, and lastly zinc. The phtcnomena of electrical ignition, whether
* The conclusions are drawn from experiments made by ^he electricity of the Voltaic apparatus.
[ 138 J
faking place in gaseous, fluid, or solid bodies, always seem to be the result of a violent exertion; ofthe electrical attractive and repellent powers, which may be connected with molions ofthe par- ticles of the substances affected. That no subtile fluid, such as the matter of heat has been ima- gined to be, can be discharged from these sub- stances, in consequence of the effect ofthe eleC' tricity, seems probable, from the circumstance, that a wire of platina may be preserved in a state of intense ignition in vacuo, by means of the Voltaic apparatus, (an instrument which will be immediately described), for an unlimitecT time ; and such a wire cannot be supposed to contain an inexhaustible quantity of subtile matter.
19. Certain changes in the forms of sub- stances, are always connected with electrical ef- fects. Thus when vapour is formed or con- densed, the bodies in contact with the vapour, become electrical. IF, for instance, a plate of metal, strongly heated, be placed upon an electrometer, and a drop of water be poured upon the plate, at the moment the water rises in vapour, the gold leaves of the electrometer diverge with negative electricity. Sulphur,,, when melted, becomes strongly electrical dur- ing the time of congelation ; and the case seems
I
[ 139 1
to be analo2;ous, with respect to nonconducting substances in general, when they change their forms.
20. As electricity appears to result from the- general powers or agencies of matter, it is ob- vious, that it must be continually exhibited in nature, and that a number of important phseno- mena must depend upon its operation. When aqueous vapour is condensed, the clouds formed are usually more or less electrical ; and the earth below them being brought into an opposite state, by induction, a discharge takes place when the clouds approach within a certain distance, con* stituting lightning ; and the undulation of the air, produced by the discharge, is the cause of thunder, which is more or less intense, and of longer or shorter duration, according to the quantity of air acted upon, and the distance of the place, where the report is heard from the point of the discharge. It may not be uninteresting to ffive a further illustration of this idea; elec- trical effects take place in no sensible time ; it has been found, that a discharge through a cir- cuit of four miles, is instantaneous ; but sound moves at the rate of about twelve miles in a minute. Now, supposing the lightning to pass through a space of some miles, the explosion will be first heard from the point of the air agitated, jiearest to the spectator ; it will gradually come
[ 140 ]
from the more distant parts of the course of the electricity, and last of all, will be heard from the remote extremity ; and the different degrees of the agitation of the air, and likewise the difference of the distance, will account for the different intensities of the sound, and its apparent reverberations and changes.
21. In a violent thunder storm, when the sound instantly succeeds the flash, the persons who witness the circumstance, are in some dan- ger; M'hen the interval is a quarter of a minute, they are secure. In a thunder storm, the lowest ground is the safest place, and a horizontal pos,- ture, the least dangerous ; the neighbourhood of trees, or buildings, should be avoided,, par-, ticularly of trees, the living juices of which are calculated to conduct the electricity, and make part of a circuit. In a house, the cellars are the safest places, and in a room the person should stand as far as possible from the fire. The means adopted by Franklin have, however, to a great extent, averted the destructive effects of atmospheric electricity; and by pointed conductors, the thunder cloud is disarmed of its terrors, and the lightning slowly discharged in harmless corruscations.
If a school-boy's kite be mounted high in the atmosphere, by means of a string, containing fila-, i^ients of metal, fastened to a cowductor, fixed on.
[HI]
a glass rod; the conductor usually gives signs of electricity, which will be greatest, when clouds are floating in the atmosphere ; and it was by means of a simple apparatus of this kind, that the American Philosopher effected his grand discovery of the identity of electricity and lightning.
The water-spout is probably the result of the operation of a weakly electrical cloud, at an inconsidei able elevation above the sea,brou2;ht into an opposite state : and the attraction of the lower part of the cloud, for the surface of the water, may be the immediate cause of this extraordinary phenomenon.
The corruscations of the Aurora Borealis, and Australis, precisely resemble strong artifi- cial electricity, discharged through rare air; and as the poles are nonconductors, being coated with ice or snow, and as vapouf must be con» stantly formed in the atmosphere above them ; the idea of Franklin is not improbable, that the Auroras may arise from a discharge of elec- tricity, accumulated in the atmosphere near the poles, into its rarer parts ; though other solu- tions of the phsenomena may be given on the idea, that the earili itself is endowed with elec- trical polarity; or that the motions of the at- mosphere produce the effect ; but all views on this subject must be hypothetical, and the light
^ t 142 J
may result from other causes than electrical action.
22. The common exhibition of electrical ef- fects, is in attractions and repulsions, in which masses of matter are concerned; but there are other effects, in which the changes that take place, operate in a manner, in small spaces of lime imperceptible, and in which the effects are produced upon the chemical arrangements of bodies.
If a piece of zinc and a piece of copper be brought in contact with each other, they will form a weak electrical combination, of which the zinc will be positive, the copper negative ; this may be learnt by the use of a delicate con- densing electrometer; or by pouring zinc filings through boles, in a plate of copper, upon a ■common electrometer; but the power of the combination may be most distinctly exhibited in the experiments, called Galvanic experiments, by connecting the two metals, which must be in contact with each other, with a nerve and muscle in the limb of an animal recently de- prived of life, a frog for instance; at the mo- ment the contact is completed, or the circuit made, one metal touching the muscle, the otiier" the nerve, violent contractions of the limb will be occasioned. If a piece of zinc and copper, in contact with each other in one point, b^j
placed in contact in other points with the sams portion of water ; the zinc will corrode and attract oxygene from the water, much more rapidly than if it had not been in contact with the copper; and if a small quantity of sulphuric acid be added to the water, it will be seen that globules of inOammable air are given off from the copper, though it is not dissolved nor acted upon.
23' The connection of chemical effects, with the exhibition of electrical pov/ers, is however best witnessed in combinations, in which these powers, are accumulated by alternations of dif- ferent metals and fluids. If plates of copper and zinc two or three inches square, and pieces of cloth of the same size soaked in a solution of salt, or sal ammoniac, or nitre, be arranged in the order of copper, zinc, moistened cloth, and so on, and made into an insulated pile, of which the series are 200 f several remarkable pheno- mena will occur.
When one hand is applied to the bottom of the pile, and the other to the top, both hands being moistened, a shock will be per- ceived.
When a metallic wire, having a bit of well burned charcoal at its extremity, is made to con- nect the two extremities of the pile, a spark will • See Plate III. fig. 15, l6.
[ 144 ]
he percdved, or the point of Uie charcoal will become ignited.
A wire connected with the top of the jsile, brought in contact with a sensible electrometer, will cause theleaves to diverge ; and by removing the wire and applying excited glass to the elec- trometer, it will be found that the electricity is positive ; a wire connected with the bottom of the pile will affect it with negative electricity * a wire from the middle of the pile will have no influence on the instrument.
If wires of platina from the extremities of the pile be introduced into water, or into two pot"- tiorls of water connected by moist substances, oxygene gas vv^ill separate at the wire exhibiting the positive electricity, and hydrogene gas at the wire exhibiting the negative electricity; and th^ proportions are such, when the proper circurri- stances existj that they will produce water when exploded by the electrical spark, that is, the volume of hydrogene will be to that of oxygene^ as two to one.
If the same wires be introduced into a strong solution of sulphuric or phosphoric acid, or into metallic solutions, oxygene will separate at the positive surface, the inflammable or metallic matter contained in the solution, at the negative surface.
When any substance rendered fluid by heat^
[ 145 ]
■consisting of water, oxygene and inflammable or metallic matter, is exposed to those wires, similar phseoomeoa occur.
When any solution of a neutral salt contain- ing acid, united to alkaline, earthy, or common metallic matter, is used ; besides the other phae- nomena that take place, acid matter collects round the positively electrified surface; alkali, earth, or oxide, round the negative surface ; and if two separate vessels are employed to contain the solution, connected by moist asbestus, it is- found, that the acid collected in the vessel con- taining the wire, positively electrified, will be in definite proportion to the matter collectedin the other cup ; that is, it will form with it a neutrosaline compound.
If a solution of muriatic acid in water, be acted on by the wires, hydrogene will separate at the negative surface, and chlorine or oxy- muriatic gas, at the positive surface.
24. This apparatus, which exhibits in so distinct a manner the relations of electrical polarities to chemical attractions, is the graijd invention of Volta, made known in the first year of this century; its electrical effects have been long known, but the phsenomena of its operation in decomposing bodies, are of n^rie recent discovery.
Several modes of constructing it have been
VOL. I, L
[ 146 ]
adopted, some of which are much superior ia point of convenience, to that which has been just described.
One mode is by^ soldering the plates of zinc and copper together, and by cementing them into troughs of baked wood, covered with ce- ment, in the regular order, so as to form cells to be filled with the fluid menstruum; each surface of zinc being opposite to a surface of copper; and this combination is very simple and easy of application.
Another form is that of introducing plates of copper and of zinc, fastened together by a slip of copper, into a trough of porcelain contain- ing a number of cells corresponding to the number of the series. The different series may be introduced separately into the troughs, and taken out without the necessity of changing the fluid, or they may be attached to a piece of baked wood (and when the number is not very large) introduced into the cells, or taken out together.*
25' Similar polar electrical arrangements to those formed by zinc and copper, may be made by various alternations of conducting and imperfect . conducting substances; but for the accumulation of the power, the series must €onsiist of three substances or more, and
•■- • ■ : - ^ » -Plate IIL fig. IT-
[147]
one at least must be a conductor. Silver or. copper when brought in contact with a solu- tion of a compound of solphur and potassa, at one extremity, and in contact with water or a solution of nitric acid, at the other extremity, some saline solution being between the sulphu- retted and the acid solutions, forms an element of a powerful combination, which will give shocks when fifty are put together ; the order is copper, cloth of the same size moistened with solution of nitric acid, cloth moistened in solu- tion of common salt, cloth moistened in solu- tion of the compound of sulphur, copper, and so on; the specific gravities of the solutions • should be in the order in which they are ar- ranged, to prevent the mixture of the acid and sulphuretted solution ; that is, the heaviest so- lution should be placed lowest.
The tables annexed contain some series, which form Voltaic electrical combinations, arranged in the order of their powers ; the substance most active beins; named first in each column.
A
[ 148 ]
Table of some Electrical Arrangements, ivhich by Combination form Voltaic Batteries, composed of two Conductors and one imperfect Conductor.
|
Zinc |
Each of the^e is the |
Solutions of nitric acid |
|
Iron |
positive pole to all the |
of muriatic acid |
|
Tin |
metals below it, and |
of sulphuric acid |
|
Lead |
negative with respect |
of sal-ammoniac |
|
Copper Silver |
to the metals above it |
of nitre |
|
in the column. |
other neutral salts |
|
|
Gold |
||
|
Platina |
||
|
Charcoal |
I'able of some Electrical Arrangements , consisting of one Conductor and two imperfect Conductors.
|
Solution of sulphur and potash |
Copper |
Nitric acid |
|
of potash |
Silver |
Sulphuric acid |
|
of soda |
Lead |
Muriatic acid |
|
Tin |
Any solutions |
|
|
Zinc |
containing acid |
|
|
other motals |
||
|
Charc( al |
The metals having the strongest attraction for oxygene, are the metals which form the positive pole, in all cases in which the fluid menstrua act chemically by affording oxygene ; but when the fluid menstrua affrjrd sulphur to the metals, the metal having; the strongest at' traction for sulphur under the existing circum- stances, determines the positive pole ; thus in a series of copper and iron, introduced inio a por- celain trough, the cells of which are filled with water or with acid solutionSj the iron is positive,
[ 149 ]
and the copper negative; but when the cells are filled with solution of sulphur and potash, the copper is positive and the iron negative.
In all coiTibinations in which one metal is concerned, the surface opposite the acid, is ne- gative, that in contact with solution of alkali and sulphur, or of alkali, is positive.
26. The energy of a combination to give re- pulsive or attractive powers to masses of matter or to affect the electrometer, seems to increase with the number of the series, as does the power to give shocks, and to decompose bodies ; but as long as the surface of the gold leaves in the electrometer, or of the human body, or of the water acted upon, is the same, and less than that of the acting plates, increase of surface of the plates is connected with no increase of power. In the operation upon metallic substances or charcoal, or upon good imperfect conductors, the case, however, is different. Thus, though a bat- tery composed of plates of copper and zinc a foot square, will not affect the condensing electro- meter more, nor decompose more water, nor give greater shocks to the fingers, than a battery containing plates of an inch square, yet it will ignite more than 100 times as much fine platina wire, and decompose sulphuric acid, and the water in strong saline solutions with infinitely more rapidity. This has been expressed by
[ 150 ]
Mr. Cavendish in the statement, that the inten- sity is the same in both cases ; but that the quantity is in some ratio as the surface. The quantity in the small plates is as much or more than such imperfect conductors as water and the human body can carry off by a small sur- face; whilst better conductors can transmit the whole quantity afforded by the large plates, even when used in very thin laminae or wires. The correctness of this view may be shewn by a very simple experiment. Let two platina wires, from the extremities of a battery com- posed of plates of a foot square, be plunged into water, the quantity of gas disengaged from the wires will be nearly the same as from an equal number of plates of an inch square ; let the fin- gers of each hand, moistened with water, be applied to the two extremities of the battery, a shock will be perceived nearly the same as if there had been no connection between the wires and the water. Whilst the circuit exists through the human body and through water, let a wire attached to a thin slip of charcoal be made to connect the two poles of the battery, the charcoal will become vividly ignited. The wa- ter and the animal substance discharge the elec- tricity of a surface, probably not superior to their own surface of contact with the metals ; the wires discharge all the residual electricity
r ]
of the plates; and if a similar expeiiment be made on plates of an inch square, there will scarcely be any sensation, when the hands are made to connect the ends of the battery, a circuit being previously made through water ; and no spark when charcoal is made the me- dium of connection, imperfect conductors hav- ing been previously applied.
The first distinct experiment upon the igni- ting powers of large plates was performed by M, M. Fourcroy, Vauquelin, and Thenard. But the grandest combination ever constructed for exhibiting the effects of extensive surface, was made by Mr. Children: it consists of twenty double plates four feet by two ; of which the whole surfaces are exposed, in a wooden trough, in cells covered with cement, to the action of diluted acids. This battery, when in full action, had no more effect on water or on the human body than one containing an equal number of small plates; but when the circuit was made through metallic wires, the phsenomena were of the most brilliant kind. A platina wire of one thirtieth of an inch in thickness, and eighteen inches long, placed in the circuit between bars of copper, instantly became red hot, then white hot, the brilliancy of the light was soon insupportable to the eye, and in a few seconds the metal fell
[ 152 ]
fused into globules. The other metals were easily fused or dissipated in vapour by this power. Points of charcoal ignited by it pro- duced a light so vivid; that even the sunshine ciDmpared with it appeared feeble.
Mr. Children has another battery in con- struction, the plates of which are double the size of that just described, and which are to be ar- ranged in pairs in single troughs, and connected by means of plates of lead in regular order.
27. The most pov/erful combination that exists in which number of alternations is combined with extent of surface, is that constructed by the subscriptions of a few zealous cultivators and pa- trons of science, in the laboratory of theRoyal In- stitution. It consists of two hundred instruments, connected together in regular order, each composed often double plates arranged in cells of porcelain, and containing in each plate thirty- two square inches ; so that the whole number of double plates is 2000, and the whole surface 128000 square inches. This battery, when the cells were filled with 60 parts of water mixed with one part of nitric acid, and one part of sul- phuric acid, afforded a series of brilliant and impressive effects. When pieces of charcoal about an inch long and one sixth of an inch in diameter, were brought near each other (within the thirtieth or fortieth part of an inch,) a bright
[ 153 ]
spark was produced, and more than half the volume of the charcoal became ignited to white- ness, and by withdrawing the points from each other a constant discharge took place through the heated air, in a space equal at least to four inches, producing a most brilliant ascending arch of light, broad, and conical in form in the middle.* When any substance was introduced into this arch, it instantly became ignited ; pla- tina melted as readily in it as wax in the flame of a common candle ; quartz, the sap- phire, magnesia, lime, all entered into fusion ; fragments of diamond, and points of char- coal and plumbago, rapidly disappeared, and seemed to evaporate in it, even when the con- nection was made in a receiver exhausted by the air pump ; but there was no evidence of their having previously undergone fusion.
When the communication between the points positively and negatively electrified was made in air, rarefied in the receiver of the air pump, the distance at which the discharge took place increased as the exhaustion was made, and when the atmosphere in the vessel supported only one fourth of an inch of mercury in the barometrical gage, the sparks passed through a space of nearly half an inch ; and by with- drawing the points from each other, the dis- charge was made through six or seven inches, * Plate III. fig. 18.
t 154 ]
producing a most beautiful corruscation of pur- ple light, the charcoal became intensely ignited, aild some platina wire attached to it, fused with brilliant scintillations, and fell in large globules upon the plate of the pump. All the phaeno- mena of chemical decomposition were produced with intense rapidity by this combination. When the points of charcoal were brought near eacK. other in nonconducting fluids, such as oils, ether, and oxymuriatic compounds, brilliant sparks occurred, and elastic matter was rapidly generated ; and such was the intensity of the electricity, that sparks were produced, even in good imperfect conductors, such as the nitric and sulphuric acids.
When the two conductors from the ends of the combination were connected with a Leyden battery, one with the internal, the other with the external coating, the battery instantly be- came charged, and on removing the wires, and making the proper connections, either a shock or a spark could be perceived ; and the least possible time of contact was sufficient to renew the charge to its full intensity.
28. The general facts of the connection of the increase of the different powers of the bat- tery with the increase of the number and sur- face of the series, are very distinct ; but to de- termine the exact ratio of the connection is a problem not easy of solution.
[ 155 3
M. M. Gay Lussac and Thenard have an- nounced, that the power of chemical decompo- sition increases only as the cube root of the number of plates ; but their experiments were made with parts of piles of a construction very unfavourable for gaining accurate results ; and in various trials made witli great care in the laboratory of the Royal Institution, the results were altogether different. The batteries em- ployed were parts of the great combination, carefully insulated, and similarly charged ; arcs of "zinc and silver presenting equal surfaces, and arranged in equal glasses filled with the same kind of fluid, were likewise used ; and the tubes for collecting the gasses were precisely similar, and filled with the same solution of potassa.* In these experiments ten pairs of plates produced fifteen measures of gas : twenty pairs in the same time produced forty nine : again, ten pairs produced five measures ; forty pairs in the same time produced seventy-eight measures. In experiments made with arcs, and which ap- peared unexceptionable, four pairs produced one measure of gas ; twelve pairs in the same time produced nine and of gas : six pairs produced one measure of gas ; thirty pairs, under like circumstances, produced 24-5 rnea-
«- Plate IV. fig. 19.
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sures ; and these quantities are nearly as the squares of the numbers,
. It would appear from the experiments of Vanmarum and Pfaff, confirmed by those of Messrs. Wilkinson, Cuthbertson, and Singer, that the increase of power of batteries, the plates of which have equal surfaces, is as the number. I found that ten double plates, each having a surface of a hundred square inches, ignited two inches of platina in wire of one eightieth of an inch ; twenty plates, live inches ; forty plates, eleven inches ; but the results of experiments on higher numbers were not sa- tisfactory ; for one hundred double plates of thirty-two square inches each, ignited three inches of platina wire of one seventieth, and one thousand ignited only thirteen inches, and the charges of diluted acid were similar in both cases.
The power of ignition for equal numbers of plates, seems to increase in a veiy high ratio with the increase of surface, probably higher than even the square ; for twenty double plates, containing each two square feet did not ignite one sixteenth as much wire as twenty, con- taining each eight square feet, the acid em- ployed being of the same strength in both cases.
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Numerous circumstances are. opposed to the accuracy of experiments made with high num- bers, or very large surfaces; the activity of com- binations rapidly diminishes in consequence of the decomposition of the menstruum used ; and this decomposition is much more violent, the greater the number and surface of the alterna- tions ; the vapour rising likewise, when the ac- tion is intense, interferes by its conducting power, and the gas by its