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a grey-white colour like the others, and weighed forty-two grains, or two fifths more than the platina employed.This was treated in the fame manner with the same quan-tity of fresh lead : the scoria; were of the fame colour, andthe bead still weighed just forty-two grains.

12. The fame author gives an account of another ope-ration, in which platina and silver were combined together,the mixture melted with lead, the lead scorified, the silverseparated by aquafortis, and the remaining platina againcupelled. He took thirty grains of crude platina, andthrice as much of the combination of silver with marineacid, called luna cornea. The mixture being exposed toas great a heat as a glass retort would bear, no liquid passedinto the receiver, but a little white matter sublimed intothe lower part of the neck of the retort, as commonly hap-pens when luna cornea is exposed to such a heat by itself.The mixt run clean together into a dark yellow hyacinthcoloured mass, and appeared well united.: the glass wasstained of a dark yellow. The mixt was pounded, alongwith pieces of the glass, which could not easily be sepa-rated, in a clean iron mortar, the powder mixed with twoounces and a half of granulated lead, and melted in a cru-cible with a strong fire : the scoria was greenish. Themetal, worked on a cupel, drove well, as in the commonsilver assay, till towards the end of the process, at whichtime it came asunder, grew flat and rough, and lookedlike silver sprung on the cupel by being too hastily cooled,but without the least metallic brightness on the surface:it was very brittle under the hammer,, but bore to be filed,and the mark of the file looked white : it weighed a hun-dred and ten grains. It was cupelled with. an ounce moreof lead, and the product was the same as before, with theloss of seven grains in weight. This last bead was beatenin pieces, mixed with six drams of pure nitre, and melted

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