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colour, and was found on trial to have a considerable quan-tity of the copper blended with it: the liquor was of amore dusky green than solutions of pure copper, probablyfrom its retaining some of the platina. Solutions of cop-per in the vegetable, nitrous, marine and vitriolic acids,mixed separately with solution of platina, produced no pre-cipitation or turbidness: Marggraf indeed found, that withthe solution in the nitrous acid, a redd ilia orange colouredpowder was deposited after long standing, but in this pre-cipitation the copper solution probably had no share, forthe solution of platina by itself, as he observes, yields, intime, a like precipitate.

VIII. Aqua regia:

Tin:

Platina.

We have seen in the third section that plates of pure tinprecipitate platina, and that they do not produce with itthe red or purple colour which they do with solutions ofgold, but a dark brownish or olive: it must here be added,for establishing the affinity more fully, that when platinais digested in a solution of tin made in aqua regia, no pre-cipitation of the tin, or corrosion of the platina ensues.The precipitation by tin is not total, any more than by themetals hitherto mentioned, but it may perhaps be question-ed whether the matter which remains dissolved, and whichgives colour to the liquor, be true platina, or the ferrugi-neous substance that was blended with it, since in a formerexperiment, page 487, after the more soluble parts of themineral had been extracted by aqua regia, the remainder,dissolved in fresh aqua regia, appeared to be completelyprecipitated by tin, the liquor proving perfectly colourless.Solution of tin, mixed with common solution of platina,seemed to have nearly the same effect as tin in substance :

a dark