340 Litclligeuce and Miscellaneous Articles. 



gas from the acetates. He endeavours to show that if they have 

 both arrived at the same conclusion, the means by which they have 

 done so are peculiar to each and have nothing in common. On this 

 subject M. Persoz recites several passages from a memoir which he 

 sent in January 1838, under the title of On the necessity of distin- 

 guishing in chemical actions the phenomenon of displacement /ran those 

 of alteration ; this memoir is still unpublished, and M. Dumas has 

 declared that he was unacquainted with it ; it contains the details 

 of experiments, from which M. Persoz states it clearly results — 



1st. That acetone contains two volumes of oxide of carbon. 



2nd. That protocarburetted hydrogen gas is derived from acetone, 

 and not from acetic acid, and consequently that the protocarburetted 

 hydrogen which arises from the decomposition of the acetates, can- 

 not be as M. Dumas supposes the immediate product of the decom- 

 position of acetic acid by hydrate of potash ; but, on the contrary, a 

 consecutive secondary product resulting — 



a. From the action which heat exerts on acetic acid, whether in 

 a free state or combined with bases. 



b. From the action which water exei'ts on acetone, one of the 

 immediate products of the action of heat on acetic acid (MM. Liebig 

 and Pelouze). 



3rd. That this pond gas is formed by the disappearance of two 

 volumes of oxide of carbon, and the assimilation of two volumes of 

 hydrogen, derived from 1 eq. decomposed water. 



From the preceding statements, M. Persoz adds, it is evident that 

 he has not adopted the views of M. Dumas in explaining the forma- 

 tion of pond gas ; and that the fact of its formation, so far from offer- 

 ing proof in favour of the theory of substitutions, justifies the 

 statement Avhich he has made respecting it, in the following pas- 

 sage of his "Introduction to the Study of Molecular Chemistry," p. 

 853. 



" When M. Dumas maintains that chlorine is isomorphous with 

 hydrogen, he lays it down as a principle, that bodies may be totally 

 changed in their elementary condition, without varying in their mo- 

 lecular composition ; we think this theory ought to be rejected as 

 being contrary to experience : it is dangerous in its application, for 

 to a certain extent it dispenses with the consideration, of the action 

 which the first products, formed during a reaction, exert upon those 

 which have not yet been altered." 



In applying then the theory of substitutions to the formation of 

 pond gas, obtained by the decomposition of acetic acid by means of 

 an alkali, M. Dumas has not excluded the action which heat exerts 

 upon acetic acid, and has thus neglected the compounds which re- 

 sult from it. He has, moreover, considered the formation of pond 

 gas as the product of a simple action, whereas it is really the result 

 of a complex one. Lastly, M. Dumas has completely neglected the 

 action which water may exert, which in the formation of pond gas, 

 acts according to M. Persoz a most important part. 



M. Dumas has lately advanced, as a new argument in favour of 

 the theory of substitutions, the fact of the identity which he has 



