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that the assayer ought to examine in this view each parcelof aqua fortis he employs, and deduct, from the weightof the gold remaining in the assay, the proportion of silverwhich that particular aqua fortis is found to leave.

The assayer’s report, of the fineness of the gold whichhe has examined, expresses the number of carats, with theodd grains or fourths of a carat, and quarters of these, bywhich it is finer or coarser than the standard. Thus stan-dard gold being of twenty-two carats, that is, twenty-four parts of it losing two in the purification ; if the massassayed lose one less, it is reported B. i car. or one caratbetter and if it loses one more, it is reported Wo. i car.or one carat worse.

By these processes gold is separated from all the knownmetallic bodies, platina excepted : if any of this was mixedwith it, nearly the whole of the platina will still remain,not destructible by the lead, and not dissoluble by theaqua fortis. If the quantity of platina is considerable, itmay be distinguished by the brittlenefs and ill colour ofthe mixt: but there are proportions of it, not sufficientto sensibly affect the gold in these respects, though theymay nevertheless deserve regard. If the gold is suspectedto be thus debased, the abuse may be discovered by thefollowing means.

After the golden plate has been weighed, and its fine-ness determined in the common method, a part of it is tobe dissolved in a little aqua regia, and a filtered colourlesssolution of any fixt alkaline salt gradually dr opt into theliquor, so long as it occasions any turbidness or precipita-tion : all the gold will fall to the bottom, with a part ofthe platina, but so much of the platina will continue dis-solved, as to discover itself by communicating a yellowtinge. This intention may be answered still more effec-tually by the æther, which imbibing the gold, and carry-5

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