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boasted of having destroyed the heterogene matter, so asto leave the gold pure, by long continued and repeatedcementations with nitre. To remove all scruples on thishead, I permitted him to make the experiment of whichl have above given a short account, and of which I haveventured to insert only such particulars as came under myown observation. The experiment, with which that ofMr. Marggraf, so far as it goes, sufficiently corresponds,was decisive. It shewed much the greatest part of theplatina changed to a powder, and the remaining platan a asremote from the. nature of gold as it was at first. I triedit both by acids, and by cupellation with lead, a process ofwhich an account will be given hereafter, and found it topreserve its own discriminating characters, without anymarks of gold, though it appeared to be purer than pla-tina in its common state. I tried also, by the same me-thods, the powders which had been separated in the ce-mentations, after the reiterated sublimations of sal ammo-niac from them; and found these likewise to be no otherthan platina, not reduced to a calx, but barely divided.

It may be presumed that the action of the nitre was notdirectly upon the platina itself, but on the irony matter,adhering to the surfaces of the grains, or more intimatelyblended in their substance; which irony particles beingchanged to a calx, the platina intermixed became dividedalong with them into a powdery state. This suppositionaccounts satisfactorily for the principal phenomena of theprocess; as the separation of the powder being plentifulin the first cementation, and more and more sparing in thefollowing ones; the first powder being of a deep colour,.and the others paler, as if the iron prevailed in the first,and the platina in the others; the powders yielding yellowferrugineous flowers with sal ammoniac, while the platinathat remained entire gave no colour to the salt.