the Attractive Powers of Mineral Acids. 8 1 
from the nitrous acid ; and though nickel feems alfo to preci- 
pitate iron, yet this arifes only from the gradual dephlogiflica- 
tion of the iron. 
Nickel precipitates copper in its metallic form from the 
vitriolic acid. It alfo precipitates copper from the nitrous and 
marine acids ; but copper precipitates arfenic from a nitrous 
folution of nickel. The vitriolic and nitrous folutions of lead 
feem to act in fpecie on nickel, that is, to diflolve it without 
any decompofition, the calces uniting to each other. The vi- 
triolic and nitrous folutions of nickel for fome time act on lead 
in the fame manner ; but at laft nickel feems to have the ad- 
vantage. With regard to the marine acid, lead feems to have 
the advantage, though a black precipitate is feen, whichever 
of them is put into the folution of the other. 
Nickel readily precipitates wifmuth from the vitriolic and 
nitrous acids ; but as to the marine I found each of thefe femi- 
metals foluble in the folution of the other, yet nickel precipi- 
tates wifmuth very {lowly, and only as to part; and wifmuth 
precipitates a red powder, which I take to be ochre, from the 
folution of nickel. 
Nickel and tin are (lightly afted on, each by the fait of the 
other ; but the precipitations are as indicated by the balance of 
affinities. 
Of precipitations of and hy cohalt. 
Cobalt is not precipitated either from the vitriolic or nitrous 
acid by zinc ; but it feemed to me to be precipitated by zinc 
from the marine acid. 
Though iron precipitates cobalt from the three acids, yet I 
found much of the cobalt retained both by the vitriolic and 
nitrous acids, particularly the latter, which, after letting fall 
Vol. LXXIII. M the 
