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the liquor became, not indeed colourless, but so pale, thatit could hardly be judged to contain anyplatina : never-theless, on putting into it some tin plates, they quicklyshewed, as in the foregoing experiment, that it held avery considerable quantity of platina. It appears there-fore that in all these circumstances the platina remainspartially dissolved in the neutralized liquor; and that onthis foundation, small proportions of it, mixed with gold,may be discovered, either by the colour of the liquor afterprecipitation with alcali, or, in a more sensible manner,by further precipitation with tin. In all the above expe-riments the solutions were diluted with water, not as be-ing a circumstance advisable where gold is to be thus exa-mined, but that the usefulness of this way of trial mightbe established with greater certainty.

Volatile alcaline salts or spirits have the same effects asthe fixt alcalies on solutions of platina, but their effects onsolutions of gold are in some circumstances different. Afterthe acid has been satiated, and all the gold precipitated,an addition of the volatile alcali beyond this point redis-solves some part of the gold, so that the liquor becomesyellow again though there be no platina in it. For thistrial therefore, only the pure fixt alcalies are to be used,which, in whatever quantity they are added, have not beensound to rediffolve any of the gold.

III. Precipitation by mineral Jixt Alcali.

The vegetable fixt alcalies serve only for distinguishingwhether gold is mixed with platina or not: they are insuf-ficient for the purification of the precious metal, as theyalways precipitate a part of the platina along with thegold. With the mineral alcali, or the alcaline basts of seasalt, the case is otherwise. Though this alcali, as appearsfrom Marggrafs experiments, precipitates, equally witl#

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