[ 66o ] 
refult was a compact, cloudy glafs, pretty tranfparent 
in thin pieces, covered in part with a thin whitifh 
coat. Towards the upper part, and all round the 
tides, were obferved feveral particles of metal ; which 
appeared to the eye like bright platina, and proved 
hard to the point of a knife. 
Remark. Nor does the glafs here feem to have 
received any thing from the platina ; the change be- 
ing no other than what white glafs is found to un- 
dergo from a flight impregnation with inflammable 
matter, 
General Remarks. 
It appears from the experiments related in this 
paper, that platina, like gold, is not adted on by 
the Ample acids, which diflolve every known metal- 
lic body befldes : That aquse regiac, the folvents of 
gold, prove likewife menftrua for platina : And that 
confequently the common methods of aflaying or 
purifying gold by aqua fortis , aqua regis , or the re- 
gal cement , can no longer be depended on : That it 
differs from gold, in giving no ftain to the folid parts 
of animals, not flriking a purple colour with tin, 
not being revived from its folutions by inflammable 
fpirits, not being totally precipitable by alcaline falts y 
that in certain circumftances it throws out gold from 
its folutions ; that thefe properties afford means of 
diftinguifhing a fmall proportion of gold mixed with 
a large one of platina, or a fmall proportion of pla- 
tina with a large one of gold j and that platina con- 
tains no gold, excepting the few particles diftinguifh- 
ed by the eye : That platina is precipitated from 
its folutions by the vitriolic acid, and by the metallic 
fubftances, which precipitated gold, though fcarce 
totally 
