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experiment with aqua regis seems liable to the fame diffi-culty ; for if the yellow grains were not gold because theydid not dissolve in aqua regis, for the same reason theyeither were not platina, or platina did not dissolve in aquaregis.

I have already mentioned the facts which induced meformerly to believe that the yellow particles mixed withplatina are really gold : fee page 487. I have since re-peated those experiments with the fame event, and madeanother which may perhaps be thought more decisive.

Twelve ounces, or 5760 grains, of platina rich in yellow■particles, were placed in three scorifying dishes under amuffle, and kept of a strong red heat for two or threehours, in order to dissipate any mercurial or other foreign•matter by which some of the yellow grains might be en-veloped. All the yellow particles, that could be distin-guished by a good magnifying glass, being then pickedout, which employed two persons for seven or eight hours,their weight amounted to 47 grains : some of them wereall over yellow ; others were in part yellow, and in partlike the grains of platina.

These picked particles were cupelled with somewhatmore than thrice their weight, viz. 150 grains, of lead,which in six different assays had yielded a silver bead amount-ing to between a 9525th and a 9527th part of its weight.The cupelled mass was of the shape of a kidney-bean, grey,rough, brittle, with a cavity in the internal part corre-sponding to the shape of the outside. The mass, brokenin pieces, was laid on a fresh cupel, and urged with a verystrong fire for five or six hours. It was less brittle thanbefore, filed smooth, and appeared of a pale yellowish co-lour.

The metal being then digested and boiled with aqua re-gia in a Florence flask, greatest part of it dissolved, a small

quantity