lOS On Cheviieal Equivalents. 



tion of the lead by a garvaiiic process, as was first shovvti by Sil- 

 vester and Grotthus. We obtain at the same time a solution of 

 acetate of zinc, equally neutral with that of the lead, and entirely 

 exempt from this last metal. No hydrogen, or almost none, is 

 disengaged during the precipitation; which proves, that the 

 whole oxygen necessary to the zinc, for its becoming dissolved 

 and saturating the acid, has been furnished to it by the lead. 



If we put into a solution of sulphate of copper, slightly aci- 

 dulous, bright iron turnings in excess, the copper is almost in- 

 stantly precipitated; the temperature rises, and no gas is disen- 

 gaged. The sulphate of iron which we obtain, is that in which 

 the oxide is at a minimum, and its acidity is exactly the same as 

 that of the sulphate of copper employed. 



We obtain similar results, by decomposing the acetate of cop- 

 per by lead, especially with the aid of heat. But since the zinc 

 precipitates the lead from its acetic solution, we may conclude, that 

 it would also precipitate copper, from its combination with the 

 acetic acid. Experience is here in perfect accordance with theory. 



We know with what facility copper precipitates silver, from its 

 nitric solution. All the oxygen which it needs for its solution, 

 is furnished to It by the oxide of silver; for no gas is disengaged, 

 and the acidity is unchanged. The same thing happens with 

 copper, in regard to nitrate of mercurj', and to cobalt, in regard 

 to nitrate of silver. In these last examples, as in the preceding, 

 the precipitating metal finds in the oxide of the metal, which it 

 precipitates, all the oxygen which Is necessary to it for its oxldize- 

 inent, and for neutralizing to the same degree the acid of the 

 solution. 



These incontestable facts naturally conduct to the principle 

 announced above, that the acid in the metallic salts is directly 

 proportional to the oxygen in their oxides. In the precipitation 

 of one metal by another, the (juantltv of oxygen In each oxide 

 remains the same, and consequently the larger dose of oxygen 

 the precipitating metal takes, the less metal will it precipitate. 



M. Gay-Lussac next proceeds to show, with regard to the same 

 metals at their different stages of oxidizement, that they require 

 of acid, a quantity precisely proportional to the (}uantity of oxy- 

 gen they may contain ; or that the acid in the salts, is exactly 

 proportional to the oxygen of the oxides. A very important re- 

 sult of this law, is the ready means It affords of determining the 

 proportions of all the metallic salts. The proportions of one 

 metallic salt, and the oxidation of the metals, being given, we 

 may determine those of all the salts of the same genus ; or the 

 proportions of acid^ and of oxide, of all the metallic salts, and 

 the oxidation of a single metal being given, we can calculate the 



oxidation 



