Tin is a brilliant, silvery-white metal. It is very malleable, but its power to resist tensile strains is so small that it is not very ductile. When bent it emits a peculiar crackling sound, arising from the destruction of cohesion amongst its particles. When a bar of tin is rapidly bent backwards and forwards several times successively, it becomes so hot that it cannot be held in the hand.
Tin is acted upon by caustic alkalies (potash and soda), but resists the acids of fruit, etc.; hence its use for coating iron so as to prevent corrosion and rust. Tin plate is sheet iron which has been coated with tin. To apply the tin the iron must be heated, and this is apt, in some cases, to injure the articles to be tinned, as it softens the iron, or in other words draws its temper. The process described under the head "Iron," page 70, enables us to avoid this difficulty.
Tin forms alloys with various metals, those of lead and copper being best known. That with lead is known as solder and pewter (see under these heads); that with copper is bronze, gun metal or " composition."
Tin and iron may be fused together in all proportions, forming apparently homogeneous alloys. Berthier describes one containing 35.1 per cent, of tin, and another containing 50 per cent, of tin, both being very brittle and capable of being reduced to an impalpable powder. The affinity of iron for tin is also well illustrated in common tin plate, which is nothing more than sheet iron superficially combined with tin, to which a further quantity adheres without being in combination. The alloy of tin and iron upon the plate, however, is so thin that it can easily be removed by mechanical friction, and the amount of tin thus alloyed is probably not much larger than one-half of one per cent. Tin, when added to pig iron, imparts to it a steel-like texture of fine grain and great hardness without very great brittleness. Such iron is easily fused, and gives a sound like a bell. Indeed, in the Great International Exhibition of 1851, there was a large bell of cast iron stated to be alloyed with a small proportion of tin. According to Karsten, pig iron with one per cent, of tin yields a somewhat cold-short wrought iron with about 0 19 per cent, of tin. Such iron, it is stated, works well under the hammer, but at a white heat white vapors escape. With more tin, the iron in welding gave much waste and produced cold-short iron, with a fine, white and dull grain. For specific purposes, however, especially where great hardness is required, iron with a small amount of tin, not exceeding 0-3 per cent, seems to be well adapted. Sterling, in England, hardens the tops of rails with tin, and according to a report of the English Commission for testing iron in regard to its adaptability for railroad purposes, the best Dundyvan bar iron, if alloyed with 0.22 per cent, of tin, supported, without breaking, a weight of 23.39 tons to the square inch. Ott fused wrought iron with 0 5 per cent, of tin, and arrived at results similar to those of Karsten. Whilst at a welding heat it worked very well, the smith stating that it was some of the toughest iron he had ever worked. The grain was found to be fine and steel-like, with strong lustre and bright color.