PLATINA, on account of its infusibility, density, and indestructibility, is one of the most important and useful of the metals yet known, and particularly for different chemical instruments and utensils, because there are few chemical agents whose effects it cannot resist. Platina is only found in the state of alloy, with rhodium and palladium, two of the newly discovered metals; and
it is accompanied also with another alloy, iridium and osmium, also newly discovered metals, as well as with particles of iron, gold, and some other substances. The discovery of these metals, and the importance of platina itself, have rendered the ores of this metal peculiarly interesting. We shall therefore in the present chapter, give a pretty full detail of the methods of analysing the ore, and of working it for the purposes of manufacture. These subjects will occupy the two following sections.
The whole of the platina which is brought to Europe, has been previously subjected to the process of amalgamation in South America; and hence it happens, that a small quantity of mercury remains in it, sometimes in very small distinct particles, but more commonly in a state of combination with gold, in the form of an amalgam. In treating the ores of platina, therefore, the first object is to separate the mercury, and the easiest process is to drive it off by means of heat, either in an open ladle, if it be not intended to collect the mercury, or in an earthen retort, if the object of the operator be to retain that metal. The platina remaining after the mercury is thus driven off, appears much yellower, because the particles of gold dispersed through it exhibit their peculiar colour. The ore is next to be spread out thin on a smooth table, and by means of a pair of common bellows, the lighter particles may be separated with tolerable