the Di folution of Metals In Acids. 377 
abounding with a fuperfluous acid, 1 threw a piece of iron, 
but no precipitation occurred. It was thence evident, that the 
faturation of the acid was not the only circumftance which 
prevented the precipitation. 
5. To another portion of the faturated folution of filver 1 
added fome red fmoking nitrous acid ; and I found, upon trial, 
that iron precipitated the filver from this mixture, and that the 
fame appearances were exhibited as had been obferved with the 
folution previoufly to its faturation. 
6. The fame effects were produced when vitriolic acid was 
added to the faturated folution of filver, and iron afterwards 
applied. 
7. To fome of the fame nitrous acid, of which a part had 
been employed to diffolve the filver, I added a piece of iron ; 
and, while the iron was aifiolving, I poured into the liquor 
fome of the faturated folution of filver; upon which a preci- 
pitation of filver took place inftantly; although, when the 
fame acid had been previoufly mixed with the folution of filver, 
and the iron was then added to the mixture, no precipitation 
had enfued. 
8. The quantity of vitriolic acid, or of the red fuming ni- 
trous acid, neceffary to communicate to the faturated folution 
of filver the property of being adted on by iron, varies accord- 
ing to the concentration, and to the degree of phlogiflication 
of the acids added ; fo that a lefs quantity than is fufficient 
does not produce any apparent efFedf. Neverthelefs, when the 
folution of filver is by addition of thefe acids brought nearly to 
a precipitable ftate, the addition of fpirit of* wine will, in a 
little time, render it capable of adting on iron. 
9. it 
Vol. LXXX. 
Ddd 
