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he introduced considerable improvements into the processes 

 employed in it. In 1 794 he was made a member of the 

 commission of agriculture and arts, and professor of che- 

 mistry at the Polytechnic and Normal Schools. 



When the Institute was organized in 1795, he became an 

 active member of it, and in the following year he was ap- 

 pointed by the Directory to proceed, in company with Monge, 

 to Italy, in order to select works of science and art to be 

 sent to the French capital. On this occasion he became 

 acquainted with Bonaparte, which led to his joining the 

 expedition to Egypt, and the subsequent formation of the 

 Institute of Cairo, the memoirs of which body were printed 

 in one volume at Paris in the year 1800. 



It has been already stated that Berthollet was an early 

 convert to the doctrines of Lavoisier, and he afterwards, in 

 conjunction with him, Guyton de Morveau, and Fourcroy, 

 planned and proposed a new and philosophical chemical 

 nomenclature. This, even with all the errors and omissions 

 necessarily attendant upon so new an attempt, has been of 

 infinite service to chemical science, and reflects great and 

 lasting honour upon its authors. He was the author of 

 more than eighty memoirs, some of the earlier of which 

 were inserted in the memoirs of the Academy; his later 

 memoirs are generally printed in the Annales de Chimie, 

 Journal de Physique, and the Memoires de Physique et 

 de Chimie de la Societe dArcueil, so called from the place 

 in which Berthollet lived, at whose house the sittings were 

 held. 



Some of the first memoirs which he published were on 

 sulphurous acid, on the volatile alkali, and the decompo- 

 sition of nitre ; in these he adopted, and for some time 

 strenuously defended, the phlogistic theory. In a paper on 

 soaps, he showed that they are chemical compounds, in 

 which the oil, by combining with the alkali, acts the part of 

 an acid. In 1785, following and extending the experiments 

 of Priestley, he proved that ammonia is a compound of 

 three volumes of hydrogen gas, and one volume of azotic 

 gas. About the same time he read a paper on the dephlo- 

 gisticated marine acid, as it was called by Scheele its dis- 

 coverer, on which occasion he renounced the doctrine of 

 phlogiston ; in his experiments on this supposed acid he 

 ifbund that water impregnated with it, when exposed to 

 light, lost its green tint, gave out oxygen gas, and became 

 common marine acid. This experiment seemed satisfactorily 

 to prove, that dephlogisticated marine acid was composed 

 of oxygen and muriatic, then called marine acid ; Berthollet 

 accordingly gave it the name of oxygenized muriatic acid, 

 shortened by Kirwan into oxymuriatic acid. In this expe- 

 riment, however, the agency of water was not taken into the 

 account, and the incorrectness of Berthollet's opinion has 

 been fully demonstrated by the experiments of Davy, Gay- 

 Lussac, and Thenard ; the name, of chlorine is now given 

 to this body, which, not having been yet decomposed, is re- 

 garded as an element. It has already been mentioned that 

 to Berthollet we are indebted for the introduction of chlo- 

 rine as a bleaching agent. In his essay on sulphuretted 

 hydrogen, in 1 778, he showed that this gas, though con- 

 taining no oxygen, possessed acid properties ; and in 1787, 

 in an essay on prussic acid, he further proved the same 

 fact, determining, by an analysis attended with great diffi- 

 culties, that this acid contained no oxygen, and consequently 

 exhibited an additional proof that oxygen was not, as La- 

 voisier had supposed, the acidifying principle. 



Berthollet was also the discoverer of the ammoniuret of 

 silver, generally called fulminating silver ; and he also first 

 obtained hydrate of potash in a state of purity, by dissolving 

 it in alcohol. His experiments on the sulphurets and hydro- 

 sulphurets contributed to elucidate an obscure part of che- 

 mistry, but they were not complete, because the nature 

 of the fixed alkalies, then unknown, is involved in the 

 question. 



In 1803 Berthollet published his work entitled Ettai de 

 Statique Chimique. In this he attempts to confute the 

 opinion of Bergman, who considered chemical affinity as 

 a certain determinate attraction which the atoms of diffe- 

 rent bodies exert towards each other, this attraction vary- 

 ing in intensity between every two bodies, though con- 

 stant between each pair. If affinity be an attraction, Ber- 

 tliollet considered it as evident that it never could occasion 

 decomposition ; he indeed admitted that decompositions did 

 happen, but he accounted for them from other causes, and 

 not from the superior affinity of one body over another : and 

 he accounted for all decompositions which take place, when 



a third body is added to two others in combination, ei'ther by 

 insolubility or by elasticity ; thus, when sulphuric acid ex- 

 pels carbonic acid from combination with ammonia, it is not 

 because the sulphuric acid and ammonia have greater affi- 

 nity for each other than the ammonia and carbonic acid, but 

 because the carbonic acid, on account of its elasticity, flies 

 off. Although Berthollet's experiments, in some degree, 

 modify the conclusions of Bergman, they by no means dis- 

 prove them ; and his opinions, though supported with great 

 ingenuity, both of reasoning and experiment, have not 

 made many converts. 



Sir H. Davy, in his Elements of Chemical Philosophy, 

 p. 117, has given an excellent synopsis of the peculiar views 

 of Berthollet, and has clearly shown that his reasonings are 

 unsupported, except by facts which are better explained on 

 different principles. ' M. Berthollet,' he observes, ' to whom 

 the first distinct views of the relations of the force of attraction 

 to quantity are owing, has endeavoured to prove that these re- 

 lations are universal, and that elective affinities cannot strictly 

 be said to exist. He considers the powers of bodies to combine, 

 as depending in all cases upon their relative attractions, and 

 upon their acting masses, whatever these may be ; and he 

 conceives that in all cases of decomposition in which 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 evi- 

 dent that there could be scarcely any definite proportions : a 

 s.alt crystallizing 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 combinations 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 accurately examined, and in 

 which there is no chance of mechanical mixture, the same 

 law seems to hold good. It is certainly possible to dissolve 

 different bodies in fluid menstrua, in very various propor- 

 tions, 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, containing indefi- 

 nite proportions ; but it is not easy to prove that in these 

 all the elements 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. 



' M. Berthollet conceives that he has proved 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 decomposition of sulphate 

 of potassa by nitric acid, one proportion of potassa may be 

 separated from the acid, and th^ other proportion may 

 combine with two proportions of acid ; phenomena analogous 

 to those of common double affinity. 



' M. Berthollet states that a large quantity of potassa will 

 separate a small quantity of sulphuric acid from sulphate of 

 baryta ; but he made his experiments in contact with the 

 atmosphere, in which carbonic acid constantly floats ; and 

 carbonate of potassa and sulphate of baryta mutually de- 

 compose each other. 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 common 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 from sulphuric acid by potassa ; but he has not 

 endeavoured to bhow in what form it appears after the 

 process. 



' M. Berthollet states that soda is capable of 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 the phenomenon 

 may be a phenomenon of double attraction. Potassa 

 has a much stronger attraction for water than soda, 

 and the soda may quit its water, and the potassa its sul- 

 phuric acid, and the effect may be assisted by the stronger 

 attraction of hydrate of potassa for alcohol. When an 

 alkali precipitates an earth from its solution in an acid, the 



NO. 245. 



[THE PENNY CYCLOPEDIA.] 



VOL. IV.-2 T 



