s 599 I

tina dissolved in the acid underneath. The oil, loadedwith the gold, appears of a fine yellowcolour, and on stand-ing for a few hours, throws off great part of its metal inbright films to the sides of the glass. The oil may betaken off from the acid before this separation happens, wellshaken with water to wash off such parts of the platina asmay adhere to it, and then set on fire in a crucible : whenthoroughly burnt out, the residuum is to be melted withnitre as in the preceding experiment. After the. sepa-ration of the oil employed at first, it may be proper, forthe greater security, to add a little more; which, if anypart of the gold should have been left in the acid, will.ef-fectually take it up.

The gold is taken up .still more readily, and perhapsmore perfectly, by the subtile fluid called æther or ætherealspirit of wine, the preparation of which has been alreadydescribed in the history of gold. Though this fluid is tooexpensive to be employed for the purification of gold in theway of business, it may be of use in the assaying of goldsuspected to be debased with platina. Indeed the purifi-cations by the common vinous spirits and essential oils arenot to be recommended to the refiner, who can better availhimself of the method pointed out in the following article.

VI. Precipitation b.y green ’vitriol.

The most effectual and advantageous method of purify-ing gold from the metallic bodies commonly found mixedwith it, appears to be,,by dissolving it in aqua regia, andprecipitating with a large proportion of a filtered, solutionof green .vitriol. Happily the same process purifies it fromplatina; the vitriolic solution precipitating the gold andleaving the platina dissolved.. See the history of gold, pagex.60 of this volume. On many repetitions of this expe-riment, _.with mixtures of different proportions of the two

metals,-,