2. Solutions of iron in the vitriolic acid, or of common green vitriol in water, which totally throw down gold, happily made no change in solutions of platina. Compositions of platina and gold being dissolved in aqua-regis, the solutions diluted with about twice their quantity of water, and a filtered solution of the vitriol gradually added; the mixtures instantly grew turbid, and, on standing, deposited the gold in form of a purplish grey calx, the whole of the platina remaining dissolved. It appeared, on numerous repetitions of this experiment, that no part of the platina was precipitated along with the gold, nor any of the gold kept suspended with the platina. Where the quantity of the mixt to be assayed was very small, the precipitation was usually performed in a filter, that the gold, which separates in very minute moleculæ, some of which might possibly remain unobserved in the bottom of a glass, might be detained on the paper. The colourless sorts of filtering-paper are preferable for this use to the coloured; as these last may be impregnated with astringent matter, which would extricate some of the ferrugineous part of the vitriol. The vitriol was dissolved in about six times its quantity of water, and a few drops of oil of vitriol added, to prevent the separation of any of its iron in the filter. This solution was put into the filter first, the solution of gold and platina immediately poured into it, the whole stirred together with a clean glass rod, and such part of the liquor, as had run thro’ before they had been duly mixed, poured back to the rest. The gold remaining in the filter was washed with fresh parcels of water, the paper cautiously rolled up, and burnt in a crucible, as mentioned in a former experiment. 3. Solutions of the vitriol, recommended by Kunckel and others for precipitating gold of an uncommonly high colour, made no change in the solutions either of gold or platina. The bluish green did indeed precipitate the gold; not as blue vitriols, but by virtue of the ferrugineous matter, of which these kinds largely participate. White vitriol was likewise made trial of, but without producing any sensible effect in either solution. 4. The experiments with green vitriol were repeated on the solutions of platina and gold made in spirit of salt. The event was the same as with those made in aqua-regis; the gold being constantly precipitated, and the platina remaining dissolved. +REMARKS+.