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Value os gold; or preventing it from being fraudulentlydebased, by the admixture of a body, endowed with somany of what have been universally reckoned the mostpeculiar and inimitable characters of the precious metal.This advantage has been obtained in the most ample man-ner that could be wished for; the experiments havingpointed out different means, by which small proportionsof platina mixed with gold, or small proportions of goldmixed with platina, may be easily distinguished, and bywhich the two metals, however blended together, may beeasily parted from one another, either in the way of affay,or of business in large. The principal of these means itwill here be proper to collect together from the differentparts of the history, and to consider them more particularlyin regard to their use and application in practice.

f. Amalgamation ioith'Quicksilver .

In an experiment related in the last section, page 579,a mixture of platina and gold being united with mercury,and the amalgam ground with water for a considerabletime, the platina was gradually thrown out, and the goldretained by the quicksilver.

This process, simple and convenient in the execution,is accompanied with some uncertainties in regard to itseffect, which render it of less general, use than it may atfirst promise to be. Repetitions of the experiment havestrewn, that though the separation succeeds in some cafes,it does not perfectly in all: that if there is any particle ofthe platina not fully dissolved by the gold, which will.generally happen unless the quantity of gold is three orfour times greater than that of the platina and the mixtureis melted with an intense fire, this part will be retained inthe amalgam, not dissolved by the mercury, not commi-nuted by the pestle,, and too ponderous to be washed off in

its