340 hitelligemce and Miscellaneom 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 phtsnomenon of displacement from 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of alteration ; this memoir is still unpublished, and M. Dumas has 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 exerts 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 which 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 
