1825.] of Claude-Louis BerthuUet . 9 



It is unnecessary, however, to detail all the separate difficul- 

 ties in which BerthoUet was involved in common with the high- 

 est intellects of his day, from the same cause, that of having the 

 mind previously warped by prejudice. Never was there a 

 system which can bear the test of cool unprejudiced examina- 

 tion less than Stahl's theory of Phlogiston. That Proteus- 

 principle, which performed the most inconsistent and contradic- 

 tory functions ; sometimes possessed of weight, tangible, and 

 easily confinable by the simplest mechanical means ; at other 

 times, imponderable, invisible, and eluding all the efforts of the 

 chemist to confine it within the compactest vessels ; at other 

 times, possessing even a principle of levity ; — the chemical 

 faith of the times, sat enthroned on the understandings of all 

 men of science. And though nothing was more simple than 

 Lavoisier's whole process of reasoning, while no result could be 

 more inevitable than his, the leading doctrines of his theory had 

 been propounded in 1773, and their proofs were nearly complete 

 in 1777 ; yet they gained no adherent of any note until so late 

 as 1785, when BerthoUet became a convert to the truth of the 

 system. So long previous to this, however, as 1777, we have 

 seen him obliged to admit in his memoir on Sulphurous Acid, 

 which was afterwards printed in 1782, that sulphur unites with 

 oxygen during its combustion and acidification, and that it is 

 heavier in consequence of it. And in another memoir, printed 

 in the same year, in his " Researches on the Augmentation of 

 Weight which Sulphur, Phosphorus, and Arsenic sustain, when 

 they are converted into Acids," he employs the same doctrine. 

 In this latter essay too, he expressly confirms the observation of 

 Lavoisier, that any given volume of air is diminished during 

 combustion to an extent, the weight of which is precisely gained 

 by the combustible. It is in a memoir read by him in 1785, on 

 the subject of Oxygenized Muriatic Acid, that he made a full and 

 manly confession of the change which had taken place in his 

 opinions, and in that very memoir combats Guyton de Morveau, 

 one of the most illustrious disciples of the phlogistic school. 



Previous to this time, however, M. BerthoUet had given to 

 the world several works, all of the highest scientific merit, and 

 some at ths same time of great practical value. Thus he was 

 the first person who took an accurate view of the constitution of 

 soaps, in his essay published in 1780, on the Combination of 

 Oils with Alkalies, Earths, and Metallic Oxides. He therein 

 showed that soaps are true chemical compounds, analogous in 

 their nature to salts, and in which the oily principle performs 

 the part of an acid. He also showed that this principle is capa- 

 ble of forming soaps, not merely by combining with the fixed 

 alkalies, potash and soda, but also with the volatile alkali, with 

 the alkaline earths, with the earths proper, with the metallic 



