[ 5*4 ]

a dark reddissi orange coloured powder precipitated, a partof the platina or its iron remaining dissolved, so as to givea high colour to the menstruum.

IX. Aqua regia:

Mercury:

Platina .

Mercury, which is said to precipitate from aqua regiano one of the common metallic bodies except gold, beingput into a diluted solution of platina, seemed to be in alittle time corroded, and did not run freely: soon after,it appeared covered with a greyish powdery matter, whichat first was apprehended to be a precipitate of the platina,but was found afterwards to be only a part of the mercurycorroded: upon applying a moderate heat, the whole ofthe quicksilver, the quantity of which was very consider-able, was dissolved, without any precipitation of the pla-tina. This solution of the two metals, being evaporateda little so as to dispose it to shoot, yielded crystals not atall like those of platina, but in form of needles, externallyof a yellowish hue: the crystals, slightly washed with proofspirit, became colourless: exposed to the fire, they emittedcopious white fumes, with a hissing or crackling noise, andleft a very small quantity of a reddish powder, giving a dullred stain to the tobacco pipe, which served for the vessel :the crystals laid on marble, and heated almost, if not quite,to a red heat, scarcely gave it any tinge or injured its po-lish. It appears from this experiment, that aqua regia,saturated with platina, is capable of dissolving a consider-able quantity of mercury, and that in crystallization greatpart of the mercury shoots before the platina.

To another quantity of solution of platina I added more.quicksilver than it was capable of taking up. The platinanow gradually fell down among the undissolved mercury,

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