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a purple, and a deep blue, and at length turned slowly toa dark purplish black colour.

The relations of platina to tin and lead appear thereforeto be very different. Though a small proportion of it istaken up and kept suspended by lead in a very gentle heat;a large proportion is not near so readily dissolved as by tin,and, when united by a strong heat, subsides in great partupon the abatement of the heat. A little quantity stiffensand hardens lead more than it does tin, but a large onedoes not near lo much diminish its malleability: a mixtureof equal parts of platina and lead, though it has nothingof the ductility which each of the metals has separately, ismuch less brittle than the mixture of equal parts of pla-tina and tin. But the most remarkable phenomena in themixtures with lead are the leafy or fibrous texture, and apurplish or bluish colour or a disposition to acquire thesecolours speedily in the air, and the black to which they atlength change. Bismuth, as we have already seen, exhi-bits with platina nearly the same appearances, though ina somewhat lower degree; and as none of the other me-tallic bodies I have tried was found to affect, or be affectedby, platina in this manner, these experiments may beadded to those of Mr. Geoffroy, in one of the late volumesof the memoirs of the French academy, for establishing ananalogy between bismuth and lead.

V. Platina with Arsenic.

White arsenic is a volatile metallic calx, reducible toits metallic form by exposing it to a moderate fire withinflammable additions. A mixture of white arsenic andfixed alcaline salt, of each one ounce, with two ounces ofpowdered charcoal, was pressed smooth into a crucible,and one ounce of platina spread above it: the crucible wasclosely covered and luted, and kept for twelve hours in a

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