BISMUTH. The minerals in which this metal constitutes the principal ingredient are comparatively few in number. Native or Oc tahedral Bismuth occurs in opaque crystals, having a metallic lustre, and a reddish silver white fracture. Bismuth-ochre is a straw coloured mineral, consisting of an oxide of the metal. Bismuth-glance is a lead-gray-coloured mineral, occurring in four-sided prisms, having a metallic lustre ; it is a sulphuret of the metal.
The pure metal, bismuth, was first shown to be a peculiar one by Stahl and Dufay : this metal generally occurs native, sometimes com bined with sulphur, but rarely with oxygen, in Saxony, Bohemia, and Transylvania. It is largely produced at Schneeberg, in Saxony, to the extent of 10,000 lbs. per annum. Bismuth is of a reddish-white colour; its lustre is con siderable, and its structure lamellated : it is so brittle as to be easily reducible to powder when cold ; it melts at about 470° or 480°. At a high temperature this metal is volatilised, may be distilled in close vessels, and solidifies in foliated crystals ; if it be merely melted in a crucible and cautiously cooled, it crystallises in well-defined cubes.
Bismuth and the metals generally combine to form alloys, and it frequently renders the metal with which it unites more fusible. Po tassium, sodium, arsenic, antimony, and tellu rium, all form alloys with bismuth. It imparts brittleness to copper, silver, tungsten, palla dium, rhodium, gold, and platinum, when al loyed with them. With mercury it forms a very fluid alloy. Newton's fusible metal is composed of eight parts of bismuth, five of lead, three of tin ; this alloy melts at 212°. Rose's alloy is still more fusible ; it is made of two parts bismuth, one lead, and one tin ; it fuses at about 201°.
Bismuth and Acids combine to form salts of bismuth, many of which are used in medicine and the arts. Bismuth is principally em ployed for the purpose of making fusible alloys and as an ingredient in solders. It is often called in the arts tin-glass. For medicinal pur poses, the subnitrate or magistery of bismuth is sometimes employed. The cosmetic termed pearl white, or Spanish white, is subnitrate of bismuth.