Tin Processing

tin processing, preparation of the ore for use in various products.

Tin (Sn) is a relatively soft and ductile metal with a silvery white colour. It has a density of 7.29 grams per cubic centimetre, a low melting point of 231.88 °C (449.38 °F), and a high boiling point of 2,625 °C (4,757 °F). Tin is allotropic; that is, it takes on more than one form. The normal form is white tin, or beta tin, which has a body-centred tetragonal crystal structure. The second allotrope, gray or alpha tin, has a face-centred cubic structure. Gray tin is theoretically stable below 13 °C (55 °F), but in practice it is readily formed only at about −40 °C (−40 °F). This transformation is difficult to initiate and is severely retarded by the presence of alloying elements or trace impurities. Nonetheless, it has given rise to the extremely rare laboratory curiosity known as tin pest.

Tin finds industrial application both as a metal and in chemical compounds. As a metal it is used in a very wide variety of industrial applications—but almost always in combination with other elements as an alloy or coating, since its intrinsic softness precludes its use as a structural material. Although tin is usually a minor constituent in alloys, it is an essential one on account of the way in which its special properties confer improvements to the matrix metal.

The major commercial applications of tin are in tinplate, solder alloys, bearing metals, tin and alloy coatings (both plated and hot-coated), pewter, bronzes, and fusible alloys. In its chemical reactions, tin exists in two valence states (II and IV) and is amphoteric (able to react as both an acid and a base). In addition, it can link directly with carbon to form organometallic compounds. These properties have given rise to many important uses for tin chemicals—for example, in electroplating, agricultural and pharmaceutical products, and plastics and ceramics.