[ 6oo ]

metals, I could never find that any part of the platina wasprecipitated with the gold, or that any part of the goldcontinued dissolved with the platina.

Mr. Schesser was the first who discovered this propertyof platina, of not being precipitated by green vitriol; andthe important consequence of it did not escape him. Heseems to think however, that the precipitation of the goldby vitriol, and washing the precipitate thoroughly withwater, are not sufficient for completely purifying the goldfrom the platina, and directs an additional operation, theamalgamation of the washed precipitate with mercury; aprocess which did not appear to me to be at all needful. .

SECT. X.

'Experiments on the yellow particles mixed with platina.

HE yellow particles, intermixed with platina as it

JL comes to us, were not only by me, but by every per-son I know of who had examined this mineral, taken tobe gold; except only Mr. Marggraf, who fays they lookedlike the finest gold, but no where hints that they were gold,and even relates some experiments which seem to provethat they were not what they appeared to be.

" On some of these yellow grains, in a parting-glass, hepoured aqua regis, and set them in digestion together. Butthough the aqua regis was made to boil, the grains werevery little acted on, the liquor hardly receiving a yellowtinge, and solution of tin precipitating nothing from it.”

" Having picked out the yellow grains from some pla-tina that had been treated with arsenic, sal alembrot, &c.he mixed them, their quantity being but small, with halfa dram of lead, and cupelled them with the lead: the pro-cess being finished, the remaining button was greyish-black, flatted, and cracked about the edges, like those ob-

tained