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wrapped up in the salts, which had not entirely melted :the silver was perfectly pure, and without the least mixtureof gold, but the gold retained about a sixth part of silver.He repeated the experiment with different mixtures ofthe two metals, and found the silver to be always purefrom gold, but that the gold retained a little of the silver,except in two instances, in which this also was pure. Heobserves, that unless the gold and silver are nearly in equalquantities, the separation does not succeed ; and that theonly nicety in the process consists in hitting the due pointof fusion, for if the fire is too long continued, or the mixtmade to flow thin, the two metals, after they have partedfrom one another, mingle again together..

We have already seen that mercury may be evaporatedfrom gold by a gentle heat : there are some other metallicbodies also, which may be totally dissipated from gold byfire, but with considerable differences in regard to thecircumstances of the separation.. Arsenic, though of itselfvery volatile, adheres so strongly to gold as not to be easilyexpelled : if the mixture is urged hastily with a violentfire, a part of the gold is carried off by the arsenicalfumes. Zinc, in open vessels, burns, changes into whiteflowers, and throws up along with its own fumes a smallportion of the gold, which tinges a part of the flowersof a yellowish colour inclining to purple : these flowersdo not rife high, part of them forms about the surface ofthe mass, and when once they are formed, they resistthe sire; so that though the whole of the zinc, by fre-quent stirring and strong fire, should be thus changed,yet, unless the proportion of gold be large, the noble metal,remains divided and interspersed among the flowers. Inclose vessels, or where the external air has no access, thezinc, by force of sire, may be totally made to sublime: itmay be expelled also in an open crucible, by beeping the

mixt