the Nature of '/owe Mineral SubJJances . 613 
experiment vi. 
1 v. o drams of turbith mineral (made by precipitating 
a folution of quickiilver in acid of nitre by a folution of 
tartar of vitriol, well edulcorated and dried), treated as 
in the firft experiment, produced thirty-fix grains of 
brown tartar of vitriol. 
Jn the firif and fecond experiments, the filver regained 
its metallic form ; in the third and fourth the lead M as 
reduced to the ifate of mafficot; and, in the fifth and 
iixth the quickiilver was totally diflipated. 
From the foregoing experiments it is clear, that com- 
binations of the acids of fea-falt and of viti'iol with di- 
ver, lead, and quickiilver, are decompofed by thefe means ; 
and alfo, that the quantity of neutral fait, which their 
acids form by combination with the alkalv, is afeertained. 
Having premiled thefe experiments on artificial fub- 
ftances, I now come to thole made with natural ones, 
which are the fubjeeft of the prefent paper. 
OF NATIVE HORN S I L V E R. 
Honi filver is found of various colours, viz. green, 
yellow, brown, purple, and alfo black. When cryllal- 
lized, it forms perfect cubes; it readily melts when put 
upon a red-hot iron, but does not fmoke; it may be 
eafily cut with a knife, for it is fomewhat malleable; we 
muft, however, except the black fort, which is brittle, 
and may be powdered. Some authors will have it, that 
4 L 2 this 
