'Examination of various Ores. 533 
poured off, and the refduum wafhed and expofed in a 
glafs matrafs to a red heat, there was no fublimate of 
fulphur, or any thing elfe obtained. The refduum , be- 
fore it was expofed to heat, did not appear to contain any 
fulphur; being of a blackifh colour after expofure to 
heat, it had a number of yellow particles mixed, which 
eafily diffolved in aqua regia. Tin being applied to the 
folution made no precipitation, which it would have 
done if thofe particles had been gold; hence we fup- 
pofed they were iron. 
The filver was precipitated from the acid by copper: 
wafhed and dried it weighed four grains, which, on cop- 
pelling with lead, loft one twenty-fourth. 
There were particles of powdered quartz apparently 
mixed with the yellow particles left after the folution. 
exp. vi. Being much difappointed in not finding any 
fulphur in the former experiment, we took three hun- 
dred grains of the fame ore. We freed it as well as pof- 
fible from heterogeneous matter : we mixed it with four 
times its weight of mild fixed vegetable alkali, put them 
into an earthen body, to which was affixed a glafs head, 
and expofed them to nearly a white heat in a naked fire 
for a full hour and an half; but no fublimation took 
place, there diftilling only a few drops df water. We 
then put the body into a melting furnace, and rendered 
Vol. LXIX. 4 A the 
