C 6 59 ] 
Remark. It feems therefore, that mercury* and gold 
cryftallize from their folutions before platina, leaving 
greateft part of that mineral difiolved. This affair, 
particularly with regard to gold, deferves farther in- 
quiry. 
Experiment io. 
As the calces of metals, obtained by precipita- 
tion from acids or by other means, vitrify along 
with fritt or glafs, and tinge them of various colours; 
and as this procefs is recommended by fome for in- 
veftigating the nature of unknown metallic bodies ; 
the following trials were made with precipitates of 
platina. 
1. Half an ounce of a precipitate thrown down 
fromfolution of platina by plates of pure tin, was tritu- 
rated in an iron mortar with eight times its quantity 
of common white glafs, the mixture put into a cru- 
cible, which was clofely luted, and placed in a wind 
furnace. The fire was gradually raifed, and kept up 
extremely ffrong for about ten hours ; when, the 
crucible being taken out and broken, the matter ap- 
peared of a dark blackilh colour, untranfparent, eafily 
friable; interfperfed with a bright whitifh matter, 
apparently metallic. 
Remark. It is probable, that this metallic matter 
y/as the platina ; and that the glafs owed its opacity 
and dark colour, not to this mineral, but to the tin 
in the precipitate, fome particles of iron abraded from 
the mortar, or other accidental caules. 
2. A quarter of an ounce of a precipitate of pla- 
tina, made by alcaline fait, was ground in a glals 
mortar with twelve times its weight of white glafs ; 
and committed to the fame fire as the foregoing. The 
4 O 2 refult 
