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distinguishing gold contained in acid solutions : whethera small quantity of some other metals may not, in certaincircumstances, accompany the gold in this separation fromthe acid, or whether very large quantities of some metalswill not defend a minute portion of gold from the actionof the æther, may deserve further enquiry; though suchexperiments, as we have hitherto made, incline us tothink that they will not. The æther imbibes the gold,though it lies only on the surface of the acid solution :nevertheless, to hasten the effect, and to secure againstany particles os the gold escaping its action, it is expedientto shake them lightly together, the vessel being closelystopt to prevent the evaporation of this very volatile fluid.If the solution in æther, poured off from the acid, beexposed to the open air, the æther exhales in a few mi-nutes, leaving the gold behind ; if kept for some monthsin a slender glass stopt so as that the æther may exhaleexceeding slowly, the gold does not resume its properform, but shoots, as is said in the Swedish transactions,into crystals, of a transparent yellow colour, a long pris-matic figure, and an austere taste.

Essential oils, shaken with solution of gold, imbibethe gold in like manner, and carry it up to the surface,but keep it dissolved only for a little time : the metalgradually separates, and is thrown off to the fides ofthe glass in bright yellow films, which on shaking thevessel fall to the bottom. The oil, though of itselfcolourless, continues coloured after the gold has partedfrom it, essential oils receiving from the pure acid, firsta yellow, and afterwards a reddish hue. Hence where•these oils are employed as a test of gold in solutions,it is not the colour which the oil acquires, but the sepa-ration of the golden films, that is to be regarded. The

oils