1825.} of Claude-Louis BerthoUet. 17 



in place of which, the modern account is that, muriatic acid 

 being compounded of chlorine and hydrogen, the hydrogen com- 

 bines with the excess of oxygen in the black oxide of manganese, 

 forming vmter, while the chlorine, a simple substance, is set at 

 liberty. This experiment, however, seemed to BerthoUet and 

 to all his brother chemists, to furnish a convincing synthetical 

 demonstration of the composition of chlorine. His analytical 

 proof was the following : 



An aqueous solution of chlorine, exposed to the light for some 

 days, gave of a qnantitii of oxygen gas amounting to nearly one- 

 third of its volume. After this evolution had ceased, no trace of 

 chlorine appeared behind, the only substance remaining in the 

 liquid being muriatic acid. Here, then, the chlorine seemed to 

 be decomposed into muriatic acid and oxi/geji. BerthoUet mea- 

 sured the volume of oxygen gas evolved, and estimating the 

 quantity of muriatic acid formed by throwino- it down with 

 nitrate of silver, he found himself able to calculate the propor- 

 tions of the supposed constituents of chlorine. The modern 

 •account of the phenomena just mentioned is, that a certain quan- 

 tity of ivater undergoes decomposition, its hydrogen combining 

 with the chlorine, and forming muriatic acid, while its oxygen 

 escapes in the state of gas. BerthoUet, however, having his 

 views of the nature of chlorine now rested on apparently the 

 strongest of all grounds, changed the appellation of Scheele 

 into that o( o.x i/genized muriatic acid; a name which it retained 

 until Sir H. Davy published his new view of its constitution in 

 1810. 



On this occasion, it is proper to observe, that the very extent 

 of Berthollet's acquaintance with chemical facts tended to mis- 

 lead his views when once they had taken a wrong bias, and to 

 strengthen the confidence he felt in this erroneous opinion, 

 Lavoisier had shortly before this shown that no metal can unite 

 with an acid, unless it be in the first place combined with a dose 

 ^^ oxygen. Now, if metaUic zinc be put into an aqueous solu- 

 tion of chlorine, it dissolves there as silently as sugar does in 

 water. There is no eflPervescence, no evolution of gas, as is 

 ordinarily the case during the solution of metals in acids, and 

 trom the liquid, by the proper chemical reagents, there may be 

 separated muriatic acid and oxide of zinc. Here, said Berthol- 

 let, the oxygenized muriatic arid imparts its oxygen to the zinc, 

 and then, the disengaged muriatic acid combines with the newly- 

 Jormed oxide, and produces muriate of zinc. In place of which 

 the modern explanation is, that the chlorine acts directly upon 

 the zinc ; and that when these two substances are obtained in 

 the state of muriatic acid and oxide of zinc, a corresponding 

 quantity of water has undergone decomposition, its hydrogen 

 and oxygen having united respectively with the chlorine and the 

 metal. 



Vew; Series, vol. ix. c 



