186 M. Dumas on the Law of Substitutions, and the 



Some examples will make these two points of view easy of 

 comprehension. 



Carbon can combine with oxygen, and thus form carbonic 

 oxide and carbonic acid. In its turn carbonic oxide combines 

 with chlorine, and produces the acid gas discovered by Dr. 

 John Davy. The electro- chemical theory should see in this 

 last an acid chloride of oxide of carbon. The theory of types 

 views it, on the contrary, as carbonic acid, in which for half the 

 oxygen chlorine is substituted. Thus the bodies C O 2 , C O Ch, 

 CS 2 are modifications of the same type*. 



Oxygenated water is a type, and one of the neatest and best- 

 defined [nets) that chemistry possesses. Supply the place of 

 the hydrogen by a metal, and you will have the binoxides of 

 calcium, barium, strontium, and in general the simple (singu- 

 liers) oxides. For these, substitute in its turn for half the oxy- 

 gen, chlorine, as is the case in chloro-carbonic acid, and you 

 will produce the decolorating chlorides. Thus oxygenated 

 water, the simple oxides and the decolorating chlorides, belong 

 to the same type, to which must also be added the compounds 

 which binoxide of azote forms with the alkaline oxides, so, for 

 example, that we may have the following series: 



H Ol 

 Of 

 BaO\ 



<U 



CaOl 



Of 



CaO 1 



Ch J 

 CaO\ 

 AzO 2 / 



These compounds of oxides and of chlorine have received 

 all kinds of definitions in the electro -chemical system. Chlo- 

 rides of oxides, of chlorites, of hypochlorites, have been made 

 of them, as people were guided by the pretended necessity of 

 always putting together in the formula of a compound two an- 

 tagonist bodies, the positive and the negative. 



This is precisely the character of the differences at the pre- 



* Here is what I said of phosgene gas in 1828: — " It is easy to see that 

 chloro-carbonic acid corresponds to carbonic acid itself. In fact, in all its 

 combinations one volume of chlorine takes the place of one half-volume of 

 oxygen; it is then as if the] oxide of carbon had been changed into acid, 

 by substituting for the half-volume of oxygen which it was necessary to 

 add, a volume of chlorine." — See my Trait e de Chimie, vol. i. p. 513. 



