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wood, wood-tar, acid, tar, islands and substances

TAPUL, ta-pool', a group of islands of the Sulu Archipelago, Philippines, lying between the Sulu group on the northeast and the Tawi Tawi group on the southwest, consisting of 38 charted and named islands and some unnamed islets; area, 77 square miles. The more im portant islands of the group are: (1) Siasi (q.v.), the largest, in the southern part of the group; (2) Bolipongpong, the most northwest erly of the group, heavily wooded; elevation, 955 feet; area, eight square miles; (3) Lapac, west of Siasi, from which it is separated by a narrow channel, with a very rugged surface; highest elevation, 1,344 feet; area, seven square miles; (4) Tapul, the name island, the most northerly of the group, fertile and under cultivation; highest elevation, 1,636 feet; area, six square miles. Though all tropical products and vegeta tion flourish in the larger islands, the chief industry is mother-of-pearl, pearl and turtle fishing; there are cocoanut plantations of value on one of the islands. Trade is carried on with Sulu, Tawi Tawi and Borneo. Pop. (estimated) 3,000. See Sur.u.

TAR, a thick, very dark liquid obtained by the dry destructive distillation of various or ganic substances. That obtained from coal, peat, bituminous shale, etc., is called coal-tar, while that from wood is named wood-tar. They are both very complex mixtures of organic substances. The substance popularly known as tar is wood-tar.

Coal-tar is collected from the hydraulic main and condensers of the gasworks as a black, oily, bad-smelling liquid somewhat heavier than water. It was formerly considered useless and a great nuisance, but, since the discovery of the value of its constituents, it has been made the starting material in many important industries. Coal tar is a very complex mixture of hydro carbons, acid and basic bodies. Its components are first separated in a rough way by fractional distillation and then each fraction is subjected to an extensive chemical treatment to separate and purify each substance therein. The hydro carbons occur in largest proportion and' they are the most valuable. Some of the important

ones are benzene (or benzol), toluene, xylene and anthracene. Of the acid bodies phenol or carbolic acid is the most important. The value of these substances lies not in themselves but in the compounds to which the chemist may pass from them. Nearly all of the varied and beautiful dye-stuffs now used are obtained from the substances mentioned above. The coal-tar colors are of exceeding brilliancy, but many are lacking in permanency (see DYEING) .

Wood-tar is a thick, dark colored, viscous material, obtained as a by-product in the de structive distillation of wood in the manufac ture of pyroligneous acid (wood vinegar) and methyl alcohol (wood alcohol). It varies some what in character with the kind of wood used. Wood-tar has many ingredients in common with coal-tar. The hydrocarbons mentioned above are present in small quantities; small amounts of carbolic acid are found with much larger quantities of homologous substances, the cresols (the whole mixture being called creo sote). Products arising from the pyroligneous acid and methyl alcohol are also found, such as acetone, methyl acetate, etc. Wood-tar is prepared in large quantities in northern Europe by a very crude and wasteful process. A hole in the ground or side hill is lined with turf and then filled with wood (usually of coniferous trees), which is afterward nearly covered with turf. The wood is burned slowly with little access to air. The tar collects in the bottom, being usually caught in an iron pan provided with an exit tube. Wood-tar has valuable anti septic properties because of the creosote it con tains. This is often separated, but the wood tar itself is much used for coating and pre serving timber in exposed places.

Tar is a stimulant and antiseptic to the skin and mucous membrane. It is used externally for skin diseases in an ointment, lotion or soap. It is found in many cough mixtures and its vapor is frequently inhaled for pulmonary troubles.