Incombustible
Cannot be decomposed, burned, or consumed by fire. See REFRACTORY MATERIALS.
India Cast Steel is a species of steel of extraordinary quality, and commonly called Wootz steel. It is imported into this country and Europe for the manufacture of fine edge instruments, etc. It is said that the celebrated Damascus blades were made of it. The process of making consists of melting small pieces of wrought iron, mixed with some twigs and dried mould, covered up well with green leaves, and luted. The crucibles are built in the form of a pyramid, inside the furnace, and exposed to a strong heat. The pieces of wootz, about as big as a walnut, are not disturbed until the crucible has cooled. The metal contains traces of silica and alumina, and about the maximum amount of carbon ordinarily found in steel. Wootz has been known throughout the East from remote antiquity. See STEEL.
India-rubber, or Gum-elastic, is the dried juice of tropical plants. It has a close resemblance to some of the gum resins, but differs from them in that the latter do not contain caoutchouc. This remarkable gum is supposed to have been discovered by a voyager on the second expedition of Columbus, who saw some natives of Hayti playing games with balls made from elastic gum. The india-rubber industry began in earnest about the beginning of the eighteenth century on a very small scale, but in 1870 there were nearly 200 manufactories in America and Europe, who consumed annually more than ten million pounds of caoutchouc. India-rubber is composed of hydrogen and carbon. Dilute acids or alkalies do not act upon the gum; but it is oxidized and destroyed by concentrated nitric acid, and charred with strong, hot sulphuric acid. It is dissolved, more or less perfectly, in melted naphthaline, benzol, bisulphide of carbon, petroleum, and the oils, both fixed and volatile. It fuses at 250 deg. F. Mr. Goodyear invented the system of vulcanizing this gum by incorporating with it from 2 to 3 per cent of sulphur, which increases its elasticity and prevents it from adhering to the moulds when subjected to pressure. Carbonate of lead and numerous other substances are also added to india-rubber for the manufacture of some special goods. If immersed in fused sulphur at 250 deg. F., india-rubber absorbs 15 per cent of the sulphur and is not materially changed. If, however, it be now subjected for an hour to a temperature of 300 deg. F., combination takes place, and vulcanized caoutchouc is the result. A further increase of temperature changes it to ebonite, or black vulcanite, a substance in great demand for the manufacture of countless articles in every-day use. If the sulphur be first dissolved in oil of turpentine, and this used for dissolving the india-rubber, the mixture remaining (after the turpentine has evaporated) will be india-rubber and sulphur, which substance can be readily pressed into plaster or metal moulds of any desired form, and the articles then vulcanized by subjecting them for an hour to a temperature of 280 deg. F. in a closed iron vessel into which steam at high pressure is admitted. See RESIN.