Thomson's St/stem of Chemistry. 141 



is, undoubtedly, sound advice, to provide a stopper before you 

 try to stop a phial with it; but it is rather unsound to desire 

 the phial to be withdrawn before you stop it; it should be 

 stopped before it is withdrawn, unless you wish the dense 

 chlorine to fall out. The Doctor's love of detracting from 

 English chemistry is displayed in this article. " The ex- 

 periments of Scheele and Berthollet were repeated and Vjaried 

 by all the eminent chemists of the time. But the first great 

 addition to the discoveries of these philosophers was made by 

 Gay-Lussac and Thenard, and published by them in 1811, in 

 the second volume of the Reckerches Physico-Chimiqiies, p. 94. 

 They shewed, that the opinion that oxymuriatic acid contains 

 no oxygen, might be supported; but, at the same time, as- 

 signed their reasons for considering the old opinion as well 

 founded. An abstract of these important experiments had been 

 published, however, in 1809; these experiments drew the at- 

 tention of Sir H. Davy to the subject." This statement is 

 mischievously incorrect. The Bakerian Lecture, read before 

 the Royal Society in December, 1808, and January, 1809, 

 contains a great many ingenious experiments on muriatic and 

 oxymuriatic acid, the constitution of which bodies was na- 

 turally one of the first objects to which Sir H. Davy directed 

 his attention, after the discovery of potassium and boron. At 

 the end of the supplement to that lecture, he says, " The pro- 

 cess in which this decomposition (of muriatic acid) may most 

 reasonably be conceived to take place, is in the combustion of 

 potassium in the phosphuretted muriatic acid, deprived by 

 simple distillation with potassium of as much phosphorus as 

 possible. I am preparing an apparatus for performing this ex- 

 periment, in a manner which, I hope, will lead to distinct con- 

 clusions." His subsequent paper, read in 1810 and 1811, 

 before the Royal Society, finally decided the difficult point of 

 chemical doctrine concerning oxymuriatic acid. The paper in 

 the second volume of the Memoires U Arcueil, to which Doctor 

 Thomson refers his readers for authority against Sir H. Davy's 

 claims, concludes thus, " Le gas muriatique oxigenc n'est pas, 

 en efFet, decompose par le charbon, et on pourroit d'apres ce 

 fait, et ceux qui sont rapportes dans ce memoire, supposer que 

 ce gas est un corps simple. Les phenom^nes qu'il presente 

 s'expliquent assez bien dans cette hypoth^se ; nous ne cher- 

 cherons point cependant a la defendre, parce qu'il nous semble, 

 qu'ils s'expliquent encore mieux, en regardant I'acide muriatique 

 oxigene, comme un corps compose." But Sir H. Davy chose 

 to defend that opinion, and succeeded in convincing the world 

 that it was the just one ; and that the hypothesis which the 

 French chemists regarded as still better, was destitute of proof, 

 and untenable. 



The experiments by which he effected this great revolution 



