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SECT. II.

Of the action of Acids on Platina.

I. Platina 'with the Vitriolic acid.

S EVERAL parcels of the purer grains of platinawere digested for some hours in a gentle heat, withthe concentrated spirit called oil of vitriol, and with thefame spirit diluted with different proportions of water.No solution happened, nor any alteration either in theliquors or the metal.

2. Three ounces of strong oil of vitriol were boiledwith one ounce of platina, in a tall narrow-necked glass,for some hours. The liquor remained nearly of the famequantity as at first, and no change could be perceivedeither in it or in the platina.

3. The glass being cut off a little above the surface ofthe liquid, the fire was gradually increased, till the liquor,which now begun to evaporate freely, had, in five or sixhours, wholly exhaled, and left the platina dry and redhot. The metal, when grown cold, being washed withwater and afterwards dried, its weight was found to bethe lame as at first, and the surface of the grains shewedno mark of corrosion. The only alteration obsorved was,that many of the grains had become dull coloured andbrownish; an effect which, as we have already seen,simple heat produces, and which therefore must not beimputed to the action of the body superadded, when aheat sufficient to produce it is employed at the fame time.

It appears therefore, that platina resists the pure vitriolicacid, which, by one or other of the above methods ofapplication; dissolves or corrodes every other known me-tallic body except gold.

Ppp 2

II. Platina