672 BITUMEN of abont 85 per cent, of carbon, and the re- mainder hydrogen with probably some oxygen. Compact bitumen, or asphaltum, has been noticed under ASPHALTUM ; but further con- sideration will be given to it in this article in treating of the uses of the bitumens. Gra- hamite, found in West Virginia, and albertite, in Nova Scotia, are supposed to be inspissated and oxygenated petroleums. Ohapapote is an asphaltum found in abundance near Havana, and elsewhere in the island of Cuba. It appears to be a consolidated petroleum, a liquid variety of which is often seen near it oozing through the fissures of the limestone rocks. The solid product is of jet-black color, and gives a brown powder and a strong but not unpleasant odor. Its specific gravity is given by Dr. Hayes at from 1 - 165 to 1'170. It melts in boiling water into a thick liquor, and forms a scum upon the surface. Alone, it melts at 214 F. into a uni- form fluid, which may be poured from one vessel to another ; calcined in close vessels, it swells and leaves a very light coke ; dissolved in spirits of turpentine, it makes a coarse var- nish. Brown-colored and viscid oils are ex- tracted from it. Petroleum and naphtha are fluid substances, called also rock oil, which flow up through fissures in the rocks, and col- lect in low places, and are found floating upon the surface of the waters of lakes. When in- durated and oxidized by exposure, they are asphaltum. The purer form, called naphtha, is very common in many parts of the world, and in numerous places is turned to good ac- count as a fuel, and also for illumination. (See NAPHTHA, and PETROLEUM.) These different varieties of bitumen are found only in the sec- ondary and tertiary formations. If they occur at all in the primary rocks, it is merely in veins and fissures, which probably have been filled long after their formation. They are very generally met with in connection with salt springs, or mines of rock salt. Near vol- canoes, petroleum is often seen issuing with the waters of springs, or floating upon the sea, furnished from springs at its bottom. The ancient Babylonians obtained the imperishable cement for their structures from the fountains of Is, which is the modern Hit, on the right bank of the Euphrates. These still continue to pour out inexhaustible supplies, mingled with the strongly saline and sulphurous waters. Common salt is also prepared here from the brine springs. The water of the springs has a temperature of about 160 F. As it flows slowly along a conduit, the oily bitumen gathers on the surface, and is skimmed off and laid in pits exposed to the air, in which it speedily hardens into flakes of about an inch thick, which are sold at Hit for about five cents the cwt. It is much used for covering the houses and boats of the region. The rock formation is an argillaceous limestone, over which is found in some places a coarsely granular gyp- sum. These fountains are celebrated as having attracted the attention of Alexander the Great, Trajan, and Julian. The bituminous products of the Dead sea in Palestine are collected on the E. and W. sides of the lake, and are supposed to be derived from a bed of bitumen at the bot- tom. The pieces resemble pitch, and, though one seventh heavier than pure water, float upon the saline water of the Dead sea, the specific gravity of which is 1-23. They melt in boiling water, and when distilled yield a vola- tile oil, some water, and traces of ammonia. The residue consists of charcoal, amounting to one eighth of the weight of the asphaltum, its ashes composed of silica, alumina, oxide of iron, and traces of lime and manganese. It is from this locality that the name Jews' pitch has been given to asphaltum. In the island of Trinidad, in the West Indies, there is a famous lake of asphaltum and petroleum called Tar lake, or by the French Le Brai, from its material answer- ing the purposes of pitch, and possessing this additional advantage, that it keeps off the tere- do or borer, which in warm climates is so de- structive to the timber of ships. The lake is near the sea, about 3 m. in circumference. It appears at a distance like water, but near by like a lake of glass. In approaching, a strong sulphurous smell is perceived at the distance of 8 or 10 miles. When the weather is hot and dry, the surface of the lake is so soft and sticky one cannot walk upon it. A foot below the surface it becomes softer, and contains an oily substance in little cells. Specimens of this bitumen, which were regarded as pure, and taken to Europe, were examined by Mr. Hatch- ett, who found them to consist of a porous and argillaceous stone thoroughly impregnated with bitumen. It does not burn readily, but becomes plastic by a slight increase of temperature. Bitumen is also found disseminated through calcareous and sandstone rocks, and saturating slates and shales. Nearly all the varieties of it are liable to have many impurities mixed with them, and all contain volatile oils and water. The bitumens are purified by first boiling them with water. The sand and other mineral sub- stances fall to the bottom, and the bitumen floating or sticking to the sides of the boiler is skimmed off and put into another boiler, by which more water is separated. It is then boiled by itself for some time, and is entirely freed from water and oils and the solid impuri- ties, which subside to the bottom. It is thus obtained in the form of a thick fatty pitch, ready to be barrelled for the market or applied to its uses. The results of the ultimate analy- sis of the pure natural bitumens, whether liquid or solid, vary but little from 88 per cent, of carbon and 12 of hydrogen. A solid bitumen of Coxitambo, near Cuenca in Ecuador, gave 88'7 per cent, of carbon and 9'7 of hydrogen, with 1-6 of oxygen and nitrogen. Nitrogen is usually present to the extent of a trace, and in the solid asphaltum it has been found to the extent of 12 per cent., and oxygen also in vhe same variety about 8 per cent. By treating asphaltum with different solvents, three dis-
