s 5*5 1

in form of a dark browniffi powder, leaving the liquor'very little coloured. Platina therefore agrees with gold inhaving less affinity to aqua regia than mercury has, thoughit differs in its affinity to the mercury, gold in this preci-pitation uniting with the mercury into an amalgam, whileplatina remains in a distinct powder. This observationaccounts for a phenomenon observed by Marggraf in thefollowing experiment.

Half an ounce of quicksilver, and an ounce of solution of*platina being shaken together, the mercury run sluggish,and soon after a quantity of yellowish white powder settledat the bottom. The solution being set to digest, it ap-peared next day somewhat greenish. The digestion wascontinued a day longer, and the mixture diluted withwater j the clear liquor being decanted off, the matter atthe bottom was thoroughly edulcorated, and the yellowishwhite powder washed off from the mercury and dried.The uncorroded mercury was not of the nature of anamalgam, but run pretty freely: being distilled in a retort,it left a metalline grain behind, so small, that its appear-ance could not well be distinguished without a micro-scope, which shewed it yellow. The white powder, setto sublime in another little retort, yielded a sublimate ofa reddish yellow colour in the lower part, and whiterabove: there remained a little grey matter, which beingpressed looked like an amalgam. It is remarkable thatthe mercury had here borne a very strong fire, by which thewhole belly of the retort had been melted, though withoutany hole being made in it.

It is probable that the little yellow grain, left upomdistilling the uncorroded mercury, was a particle of goldwhich the platina had contained; and that, agreeably to-the foregoing remark, platina and gold, dissolved togetherin aqua regia, may be parted on this principle, the gold

being,