Asphaltum, Or Asphalt (Gr. , a mixture of different hydrocarbons, some of which contain oxygen, by the majority of chemists and geologists supposed to be of vegetable origin, while others derive it from the remains of animals. It is also called bitumen, mineral pitch, and Jews' pitch (from Lacus Asphaltites). (See Bitumen.) It is more bituminous than the coals, and when pure is of the consistence of resin; but the consistence varies with the temperature and with the amount of liquid bitumen or petroleum which may be mixed with it, hold-ing the more solid asphaltum in solution. It is often intermixed with stony substances, and sometimes even contains 80 per cent. of carbonate of lime. Pure asphaltum is soluble in oil of turpentine, naphtha, and carbonates of the alkalis, but insoluble in water; alcohol dissolves out of it about 5 per cent. of a resinous substance, and ether takes up 20 per cent, of another resin that is not affected by the alcohol. It yields also a volatile oil. The remainder is a substance named by M. Boussingault asphal-tene, the composition of which is C20H16O3. Asphaltum burns readily, with a red smoky flame, and leaves no ashes except those due to its impurities.
Its specific gravity ranges from 1 to 1.8; its color is black and dark brown, and it does not soil the fingers. It melts at the temperature of boiling water, and consequently is unfit for use as fuel, and cannot be economically used for gas. Most of the geological formations contain it, but it is particularly common in the secondary and tertiary calcareous and sandy strata. In the primary rocks it is found only in small veins. It is obtained in large quantities on the shores of the Dead sea, rising to the surface, where it forms solid lumps which are thrown on the shore. Some of the 'other noted localities are a lake on the island of Trinidad, 1 1/2 m. in circumference, which is hot at the centre, but is solid and cold toward the shores, and has its borders over a breadth of three fourths of a mile covered with the hardened pitch, with trees flourishing over it. The inhabitants powder the asphaltum and drive it by a blast upon burning coals; thus used it gives out as much heat as an equal weight of the best English coal. It is thrown over bagasse or wood fuel in the manufacture of sugar.
At various places in South America are similar lakes, as at Caxatambo and Beren-gela, Peru, where it is used for pitching boats; in California, near the coast of Santa Barbara. It occurs in smaller quantities, disseminated through shale and sandstone rocks, and occasionally limestones, or collected in cavities or seams in these rocks, in Derbyshire, Cornwall, and the French department of Landes; and at Val de Travers, Neufchatel, impregnating a bed in the cretaceous formation, and serving as a cement to the rock, which is used for buildings. Grahamite from West Virginia, described by Prof. Wurtz of New York in 1865, resembles asphaltum in its pitch-black lustrous appearance. - A rigorous analysis applicable to all asphaltum cannot be given, as each bed may present different results. The following ultimate analyses have been made:
Nos. 1 and 2 were by Ebelman, No. 3 by Weth-erill. The action of heat, alcohol, ether, naphtha, and oil of turpentine, as well as the above analyses, show that the so-called asphaltum from different localities is very various in composition, and that the true composition of any one of them is not known. They contain volatile oils, heavy oils, resins soluble in alcohol, solids soluble in ether but not in alcohol, other solids not soluble either in alcohol or ether, and nitrogenous substances. - Asphaltum was used by the ancient Egyptians in embalming, and appears to have been employed in the construction of the walls of Babylon. It is now used for pavement, for making water-tight tanks, as a coating for tubes of glass and iron used for conveying gas or water, and for various other purposes of like nature. Asphalt is used in Paris in two different forms: first, the natural rock, unalloyed, with which streets are paved; second, a mixture of asphalt with bitumen and fine gravel for the construction of sidewalks. The rock is found principally at Seyssel and Val de Travers, and is transported to Paris by canal and rail. Pure asphaltic rock is preferred for streets and roads.
When this is heated to near 300° F., it crumbles to a mass of brown powder, which when compressed in a mould and allowed to cool recovers its original hardness and appearance. If the hot powder, instead of being placed in a mould, be spread about two inches thick on a hard foundation and pressed or packed by a hot iron pestle or roller and allowed to cool, the surface will immediately solidify, forming a crust identical with the original rock. The discovery of this application was due to accident. Fragments of asphaltum, dropping from the carts which transported it from the quarries along the road, became heated by the sun and were crushed to powder and compacted by the continual passage of carts, until they formed a hard, smooth track. The matter was investigated, and led to the present method of asphaltum road making. The sidewalks of Paris are made of mastic of asphaltum, with an addition of bitumen and fine gravel, and can be more properly described under Pavement. - Artificial Asphaltum is made from bitumen or the refuse tar of the gas house. Coal tar is heated to a degree that renders it hard and brittle; of this 25 parts are mixed with 50 parts slaked lime in fine powder and 75 parts river gravel.
These ingredients are thoroughly incorporated in a cast-iron boiler, heated for two hours, and drawn off into moulds. The blocks thus obtained are treated subsequently like mastic of asphalt for sidewalks, except that the temperature is carried higher. Another patent gives the following proportions: Residue of tar containing considerable non-volatile oil, 25 to 50 per cent.; carbonate of lime in dry powder, 50 per cent.; silica and clay, 25 per cent. This is stirred in a boiler over a slow fire for ten hours and run off into moulds. The mineral constituents must be previously strongly heated to expel air and moisture, in order to facilitate the thorough incorporation with the pitch. Artificial asphaltum is used for coating gas pipes to protect them from corrosion; also for sidewalks, roofing, flooring, especially for stables, and water-tight tanks. A concrete prepared of 95 lbs. asphaltum, 5 lbs. bitumen, and 150 lbs. broken stone, has been employed in France for marine constructions. The use of prepared asphaltum in the United States has been largely increased since the discovery of petroleum and of a deposit of a solid hydrocarbon called Grahamite, and also in consequence of the great extension of gas manufacture by which the supply of raw material has become practically inexhaustible.