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rate upon the alloy and not upon the gold, as by thosewhich act on the gold itself and not on the alloy.

A small portion of the gold is commonly retained inthe sulphureous scoriæ, along with the silver or othermetals with which it had been debased. The scoriæ ofthe last fusions, in which the sulphur and metal of theantimony have suffered little separation, are therefore tobe reserved for the same purposes again. From those ofthe first, both the gold and silver may be recovered, bykeeping them in fusion in a crucible, and blowing off theantimonial matter, in the manner above directed for dissi-pating it from gold.

V. Purification of gold from platina, silver and base met ah

by aqua regia.

Aqua regia, in dissolving gold, leaves behind whatsilver the gold had been mixed with ; and certain bodies,added to the solution, separate the gold from it, withoutbeing able to separate any metal besides; so that on thisprinciple gold may be brought with ease to its ultimatepurity.

The gold, flatted into thin plates or reduced into grains,is to be put into about thrice its weight of moderatelystrong aqua fortis, and the vessel being set in a gentleheat, a little sea salt is to be added : the dissolution willimmediately begin, with a considerable effervescence, andwhen the action ceases, the addition of a little more seasalt will renew it: the injection of sea salt is to be con-tinued, by a little at a time, till the whole of the goldappears to be dissolved; the quantity of salt requisite isgenerally about a third of the aqua fortis. The clear partof the solution is to be poured off, and the remainderpassed through a double filter of paper : the undissolved1 matter