TAPTI, a river of the British presidency of Bombay, India, rises in the Saugur and Nerbuddah territories, in lat. about 21° 46' n., flows w. through Sciudhia's dominions and the districts of Candeish and Surat to its mouth in the gulf of Cambay, 17 m. below the town of Surat. It is 441 m. in length; but can hardly be said to be navigable, for even small vessels of from 40 to 50 tons burden cannot ascend higher than Surat.
TAB, is a well-known substance, for which it is difficult to frame a definition, since it varies in composition, color, and consistence, and is derived from all three kingdoms of nature. In various parts of the world it occurs as a natural mineral product, and is known under the various names of bitumen, asphalt, petroleum, natural tar. See NAPHTHA. As an animal product, a species of tar is obtained from the destructive dis tillation of bones employed in preparing bone-black. The distillate, which possesses a most offensive odor, separates into a heavier layer of black animal tar—commonly known as bone-oil, or Dippers animal oil—and a lighter layer of watery solution of sesquicar bonate of ammonia, commonly known as bone-ligtor, and much employed in the prepar ation of various salts of ammonia. This animal tar is chiefly used for the lubrication of machinery. The vegetable kingdom is, however, the most important source of tar. On submitting wood to destructive distillation in closed vessels, we obtain a large number of products, which are described in the article WOOD, DISTILLATION OF; some are gase oas and some liquid, and of the latter one portion is soluble and the other insoluble in water. This insoluble portion constitutes wood-tar, and is composed of a mixture of various liquids holding solid matters in solution or in suspension. Among its most important constituents, professor Miller mentions several forms of hydrocarbon, such as toluol, Ci4B8; cymol, and eupion, besides a number of oxidized compounds, including creasote, picamar, and kapnomar, C90IIii02; while among the solid portions are resinous matters resembling colophony, and a waxy sub stance named paraffin, and many other substances, such as naphthalin, cedriret, pittacal, pyrene, chrysene, Ci2H, ; and pyroxanthin. (When the formula is not given,
the exact composition of the substance is not determined with certainty.) The Stock holm tar, which is so widely used in shipbuilding, and the American tar, which is almost equally celebrated, are chiefly prepared from the resinous wood of the pine, and especially of the root of the tree. The specific gravity of ordinary tar is about 1.040. Peat yields a tar very similar to wood-tar. Coal yields, on distillation in closed vessels, even a larger number of products of distillation than are yielded by wood. In addition to numerous gaseous products, the liquid portions contain water and various forms of hydrocarbon, which collectively form the liquid known as coal-naphtha; besides which there is a large quantity of a dark viscous matter known as coal-tar. The mixture of naphtha and tar is described in this work under the title of GAS-TAR. For an account of the beautiful coal-tar colors or aniline dyes, see the artidles DYE-STUFFS and PHENYL. The distillation of coal-tar is conducted on an extensive scale as a separate branch of trade. From Miller's Organic Chemistry we extract the following remarks on the com pounds present in this substance: "Of the substances contained in coal-tar, some are basic, and some acid, but the principal portion consists of neutral or indifferent bodies. The bases include ammonia, aniline, picoline, quinoline, and pyridine. Among the acids, the acetic is present in small amount; but the most important is phenic acid, the carbolic acid of Runge: This chemist also mentions two other acids named rosolic and brunolic acids. The neutral substances contain several hydrocarbons, including benzol, toluol, cumol, and cymol, which are among the liquid constituents; while naph thalin, anthracene, chrysene, and pyrene are among those which are solid at ordinary temperatures." When either wood-tar or coal-tar is submitted to distillation, the solid brown or black residue left in the retort constitutes pitch.