ASPHALT, or ASPHALTUM, is the name given to a bituminous substance of a solid con sistence. See BITUMEN. It probablogwes its origin to vegetable matter which has been subjected to a slow process of decomposition or decay, resulting in the production of a bituminous coal, from which, by volcanic agency, the A. has been distilled and diffused over the neighboring district. largest natural deposit of A. is in the island of Trini dad, where the plain known as the Pitch lake is found. See TRINIDAD. The A. from Trinidad is largely used for ships' bottoms, and is reputed to kill the teredo or borer, which proves itself so very destructive to the wood of ships in tropical regions. A. is also found on the shores of the Dead sea in large quantity, and is known to the Arabs by the name of kajar mottsa, or Moses's stone. It likewise occurs in South America at Coxitambo near Cuenca, in Alsace, and other parts of the European continent, in east Lothian and Fifeshire (Scotland), in Shropshire, etc.
During the manufacture of coal-gas, much tarry matter is evolved from the retort, and is received in the coolers or condensers. If this tar be subjected to partial distilla tion, naphtha and other volatile matters escape, and an artificial A. is left bdhind, which possesses the principal properties and can be employed for the majority of purposes to which native A. is applied. The various kinds of A. have a pitchy odor, are of a black or dark-brown color, but do not soil the fingers; are insoluble in water, sparingly soluble in alcohol; but are in great part dissolved by ether, oil of turpentine, and naphtha. Petroleum (q.v.), or rock oil, is a native liquid bitumen, which largely exudes from crev ices in rocks in many districts, and is essentially A. dissolved in naphtha. The specific gravity of A. is very near that of water, ranging from 1000 to 1100. When set fire to, it burns readily with a smoky flame, and is often used in the smaller gas-wbrks as fuel.
by being'allowed to run very slowly into the furnace-fires. A., besides being employed for coating the exterior of ships' bottoms, is also used, in a heated condition, for saturat ing timber which is intended for piles in the construction of breakwaters, river-bridges, and other situations where the combined action of the air, water, and minute animals would soon render ordinary wood rotten and useless. Wooden houses may be preserved in the same manner by a coating of A. applied externally; and ground-floo•ing placed in damp situations is much the bdtter for the spaces between the planks being filled up with A.
About 1840, A. began to be generally used for foot-pavements in cities, and also for floors of cellars and out-houses. For purposes of this nature it is heated in portable boilers, into which, at a certain stage of the preparation, there' is poured a quantity of thoroughly dried sand, gravel, or powdered limestone, which is well mixed with the liquid A. The mixture is then spread on the spot prepared it; and when cool, forms a hard kind of pavement. Of this method of forming footways, high expectations were at first formed; but latterly the process of asphalting has gone out of use in England, as it is found not to be so durable as stone. and therefore, in ordinary circumstances, more costly. Pu Paris, however, asphalting is still extensively practised in the more spacious thoroughfares. The better kinds of A. are used in the manufacture of the black varnish, which is employed in forming the enamel which coats the variety of leather known as patent leather. A. is not of itself used in medicine, but its natural solution in naphtha, viz., petroleum, is a valuable agent when applied either externally or internally. The synonyms of A. are—liatie6 pitch, mineral pitch, Jews' pitch, Dead Sea bitumen, compact bitumen, Trinidad bitumen, and maltha.