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I. Of the mixture of gold with mercury: Gold powder,water-gilding , &c.

Mercury, in the greatest cold that obtains in our at-mosphere, acAeres readily to gold, totally conceals itscolour, communicating a silver whiteness to every part ittouches, and by degrees penetrates and dissolves it. Someof the chemists speak of an animation of mercury, bywhich its activity on gold is greatly increased ; and Mr.Boyle relates, that he had himself prepared mercury, soas to dissolve half or even equal its weight of gold leaf,and to produce, during the dissolution, a sensible heat,sometimes considerable enough to be offensive to the hand :but an enquiry into this point belongs rather to the historyof mercury than of gold.

In order to obtain a smooth amalgam, or uniform mix-ture, of gold and common mercury, the union is expe-dited, by reducing the gold into thin plates or grains jwhich are heated red hot, and in this state thrown into asmuch mercury, as will cover them, previously heated inanother crucible, till it begins to smoke : on stirringthem together with an iron rod, the gold soon dissolvesand disappears. If the amalgam is designed for any niceuses, it should be cleansed, from any filth it may havecontracted, by grinding it in a glass, stone, or woodenmortar, with some common salt and water, and occasion-ally renewing the water, till the amalgam ceases to dis-colour it, and appears of a pure vivid brightness.

When the proportion of mercury is large, so that themixture continues fluid when cold, a considerable partmay be separated.by pressing it through soft leather, as thethicker kind of wash-leather or doe-skin : so much ofthe quicksilver may be squeezed out, as to leave a butyra-ceous or consistent mass, containing little more than one

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