the Oxidation of the Metals, &c. 20} 
acid some well cleaned iron filings, and in a large propore 
tion, the copper is precipitated almost instantaneously, the 
temperature 1s considerably raised, and no gas is extricated. 
The sulphate of iron which we obiain is that in which the 
oxide is at the minimum, and its acidity is precisely the 
same with that of the sulphate of copper employed. 
We obtain similar results by decomposing the acetate of 
copper by lead, particularly by the help of heat. Bui since 
zinc precipitates lead from its acetic solution, we must 
conclude that it would also precipitate copper from its 
combination with acetic acid. Experience in this case 
accurately agrees with theory. 
We know with what facility copper precipitates silver 
from its nitric solution. The whole oxygen which it re- 
quires to dissolve it is furnished by the oxide: of silver ; for 
no gas is extricated, and the acidity does not change. 
It is also the same case with copper as with nitrate of 
mercury, and with cobalt with respect to the nitrate of 
silver. 
In these Jast examples, as in the foregoing, the precipita- 
ting metal finds in the oxide of the metal which it preci- 
pitates, the whole of the oxygen which is necessary to 
oxidize it, and to neutralize to the same degree the acid of 
the biloba 
These facts, which appear to me to be incontestable, 
naturally lead to the principle which I bave given out, 
namely, that the acid in the metallic salts is directly i in pro- 
portion to the oxygen in their oxides. For since the pre- 
cipitating metal finds in that which is precipitated ail the 
oxygen which it requires to oxidate it, and to neutralize to 
the same degree the acid of the solution; it follows that 
the quantity of oxygen in every oxide remains the same; 
and consequently the less of the precipitating metal is dis- 
solved, the more affinity it has for oxygen. Thus if we 
suppose two metals, one of which tikes stwiee! as much 
oxygen as the other, it will dissolve twice as much of the 
latter as of the former, in order to neutralize the same 
quantity of acid. 
It is therefore proved, that when zine, iron, lead, cop- 
per, silver, cobalt, and mercury are precipitated from their 
solutions in the metallic state, the precipitating metal finds 
_1n that which is precipitated all the oxygen necessary to 
oxidize it, and to neutralize to the same degree the acid of 
the solution. The other metals ought also to enjoy the 
same property ; but there are some circumstances which I 
shall make known, which render it difficult to prove it. 
If 
