the Dijfoluiion of Metals in Acids. 2 g„ 
in its metallic ftate. I do not recoiled!, that the precipitation 
of a iolution of filver by the fame martial vitriol has been ob- 
leivcd. however, upon pouring a Iolution of martial vitriol 
into a folution of filyer in the nitrous acid, a precipitate will 
be thrown down, which acquires in a few minutes more and 
more of a metallic appearance, and is indeed perfed fiver. 
When the two folutzons are pretty concentrated, a bnpht ar- 
gentine film fwims on the furface of the mixture, or filvers 
the tides of the glafs in which the experiment is made. When 
a phlogifticated iolution of filver is ufed, the mixture is black- 
ened, as happens generally to a folution of martial vitriol, 
when a phlogifticated nitrous acid is added to it. 
I added about equal parts of water to a mixture of a phlo- 
gifticated folution of filver and a folution of martial vitriol, in 
which all the filver, had been precipitated, and digefted the 
diluted mixture with heat, by which means mail of the pre- 
cipitated filver was re-diffolved. Bergman has obferved a 
fimilar re-diffolution of gold precipitated by martial vitriol upon 
boiling the mixture ; but he attributes the re-difiblution to the 
concentration of the aqua regis by the evaporation. As this 
explanation did not accord with my notions, I diluted the mix- 
ture with water, and found that the fame re-diffolution occur- 
red both with the folution of filver and with that of gold. 
But vvith neither of the metals did I find that the re-diflolution 
evei took place, unlefs there had been a fuperabundant acid 
in the folutions of gold and filver employed. 
28. Mercury is alfo precipitated in its metallic ftate from its 
folution in nitrous acid by a folution of martial vitriol. When 
the liquor is poured off from the precipitate, this may be 
changed into running mercury by being dried near the fire. 
29. I 
