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mixtures, the white one possibly from the mercurial glo-bules united with the acids, and the yellow from the fer-rugineous parts. The author himself concludes from theexperiments, that the acids have no action on the true pla-tina, but attack in some measure its ferrugineous matter jand that the marine acid seems to have this effect in agreater degree than the other two.

V. Plasma with aqua regia.

1. Aqua regia, the proper menstruum of gold, beingpoured upon platina, begun to act upon it slightly in thecold, and by the assistance of heat slowly and difficultlydissolved it; acquiring at first a yellow colour, whichdeepened by degrees, as the menstruum became more satu-rated, into a dark, almost opake, brownisli red.

2. The experiment was several times repeated, withdifferent forts of aquæ regiæ, made by dissolving sea faitand sal ammoniac, separately, in four times their weight ofaquafortis, and by abstracting the nitrous spirit in a retortfrom the same proportion of each of the salts. All thesemenstrua dissolved the platina; and it did not appear tome that one dissolved it more readily, or in greater quan-tity than another. Mr. Macquer tried also several aquæregiæ, composed of different proportions of the nitrousand marine acids, and found that a mixture of equal partsof the two spirits was one of those which answered thebest.

3. In order to determine the quantity os menstruum ne-cessary for the dissolution, I prepared an aqua regia by di-luting ten ounces and a half of strong smoking spirit of nitrewith eight ounces of water, and abstracting the mixturefrom fix ounces of common salt. Five ounces of thisaqua regia,which may be reckoned to contain three ouncesof very strong acid spirit, were poured upon one ounce of

Q_q q platina,