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its gross form. Various mixtures of platina and goldwere treated in the manner above described; and the gold,recovered from the amalgams, was submitted to furtherexaminations. Where the proportion of platina was largeat first, the microscope almost always discovered somegrains of it remaining with the spongy mass of gold afterthe evaporation of the mercury; and even when the goldhad been melted, and made fluid enough to be poured intoa mould, I have sometimes seen distinct grains of platinaon the fracture of the ingot. Where the proportion ofplatina had been small, the recovered gold was frequently,but not constantly, found to be pure.

It appears therefore, that though mercury has a greateraffinity to gold than to platina, and though platina, on thisprinciple, is capable of being separated from gold; yet theprocess is too vague and precarious to be applicable in theway of assay, as we can have no mark of the precise timefor discontinuing it, and as we can never be certain, with-out making another assay, whether the whole of the platinais separated or not. As a preparatory operation, wherethe quantities of platina and gold to be parted are large, itis nevertheless of good use; as greatest part of the platinamay by this means be washed over with little trouble, andthe gold brought into a less compass, so as to be commo-dioully submitted to a further purification by the meanshereafter pointed out.

This process may be considered as answering the samepurpose, in regard to mixtures of gold and platina, as thatof stamping and washing does in metallic ores,which couldnot be reduced to pure metal in the furnace to advantage,without the previous separation of great part of their earthyor stony matter by water. To ensure success, the mixt, itbrittle enough to be pulverable, should be reduced intovery fine powder, in stamping mills, or in an iron mortar: