Platina, one of the most precious metals that was discovered in South America, about the middle of the eighteenth century. It is found chiefly in the river Pinto, and near Carthagena, in small, irregular grains, which are always combined with iron.
Platina retains its metallic lustre, in a manner similar to gold ; nor does it become tarnished on expo-sure to the air : it is, however, extremely difficult of fusion, requiring an intense heat to reduce it to a fluid state. When properly refined, its colour is between that of iron and silver : it emits no smell; is reputed to be the most ponderous body hitherto known ; and its specific gravity is, according to Mr. Kirwan, to that of water, as 23 to 1.—Farther, platina is considerably harder than iron , and, remaining equally exempt from the effects of fire and air, it forms tie best material for making crucibles. It resists the action of acids, sulphur, and alkalies ; and, notwithstanding its uncommon hardness, is extremely duct ile, so that it may Be rolled into plates, or leaves, like those manufactured from gold; and Dr. Withering observed, that the wire of platina is much stronger than that of silver or gold of a similar thickness.
Lastly, platina possesses the property of soldering, or welding, without mixture, on which account it is preferable to gold. When formed into a mirror, the former metal reflects one image only, while it remains unchangeable like glass.