Page:The New International Encyclopædia 1st ed. v. 02.djvu/170

ASPHALT. together than the previous ones, the last set being three inches apart. From this crusher the fragments go to a steam-heated drum melter, which reduces the material to a mushy state. Next naphtha is added, dissolving the asphalt proper and leaving the sand below. The sand is treated a number of times, until the asphalt has been practically exhausted, after which the sand is wasted. The combined solution of naphtha and asphalt flows by gravity for 30 miles, through a 5-inch steel pipe-line, to Alcatraz Landing. Here the naphtha is recovered by distillation and pumped back to Sisquac to be used again. The asphalt left after the distillation is then barreled and shipped.

The California maltha already mentioned is refined as follows: The bituminous sand is thrown into a steam-jacketed cylinder with revolving arms, where it is broken into fragments. It is then placed in boiling water, whereupon the maltha floats to the top of the vat, the sand settles to the bottom, and is removed mechanically. The crude maltha is sent to a storage tank, then to a refining kettle, where the volatile matter is evaporated, the temperature being increased from 100 to 240° F. during the 24 hours of final treatment.

Asphalt is also produced in California by distilling crude petroleum oil, the heat being applied through steam-coils. The kettles are open at first, then closed, the temperature being increased during the process from 220° F. to 700° F.

Trinidad Lake asphalt is refined, or has its water and volatile matter driven off, by heating it in tanks about 10 feet square and 15 feet high. The heat is applied by means of steam-coils placed in the tanks. To keep the mineral matter from settling, jets of steam are passed into the bottom of each tank. The steam-pressure employed is about 100 pounds, giving about 325° F. At this temperature the asphalt is a liquid, so that after the water has been driven off the refined product can be run into barrels for shipment. In the older method of refining, the heat was applied by means of a fire, which was directly in contact with the vessel containing the asphalt. Aside from the danger of overheating, this process was objectionable because it required 6 to 7 days, instead of the 12 hours taken by the new process. In addition, the sedimentary matter settled to the bottom of the old tanks, and was lost; whereas it is now retained as a valuable component of the asphalt.

Aside from such of the rock asphalt as is used for paving, most of the asphalt of commerce is a refined product, or else the latter made into either asphaltic cement or mastic. Asphaltic cement is refined asphalt, tempered with residuum petroleum oil, maltha, or some other material, but generally the oil. From 15 to 18 pounds of oil is added to 100 pounds of refined asphalt, the amount of oil varying with the uses to which the cement is to be put. The two ingredients are mixed while hot, being agitated by mechanical means or by air. Mastic is prepared from crushed or powdered rock asphalts, and also from refined asphalt. Either asphaltic cement or maltha is used with the rock asphalt, and sand and perhaps powdered limestone with the asphaltic cement. The mixture is made under heat, and is run into molds for shipment. When used for floors, sidewalks, or roofs, the mastic blocks or cakes are melted, refined asphalt and sand or fine gravel are added in small quantities, until the desired consistency is attained. Powdered limestone may be used in place of gravel or sand, particularly where a hard, dense, impervious final product is desired. Asphalt concrete is simply crushed stone or gravel bound together with mastic, the two mixed hot and compressed after being put in place. Some of the most important uses to which asphalt is put are for pavements, pipe coatings, and reservoir linings. See ;.

For further information on mining and refining, consult: Tillson, Pavements and Paving Materials (New York, 1900); J. W. Howard, Natural Asphaltum and Its Compounds (Troy, N. Y., 1894); The Mineral Industry, Vol. VII. (New York, 1898); Henry, "Some Facts Relating to the Asphalt Paving Industry" (originally in The Polytechnic, Troy, N. Y.; also abstracted in Engineering News, New York, March 4, 1900). See ; ; ; ;.

ASPHAL'TIC COAL, or ASPHAL'TITE. Solid forms of asphalt, originally derived from petroleum, which, through loss of their oil content, have assumed an appearance analogous to that of glance-coal. Asphaltic coal occurs usually in fissures, into which it has flowed while in a liquid or viscous condition. Such fissure deposits have been found in rocks of Devonian, Carboniferous, and Tertiary Age, and the contained material has received various names in different portions of the country. The chief uses of these asphaltic coals are as bases for varnishes, as insulators, and formerly, to a large extent, as gas-enrichers. The more important varieties, with the localities where mined, are: Albertite, Albert County, N. B., Canada; gilsonite and uintahite, in the Uinta Mountains of Utah; grahamite, originally from Wood County, W. Va., but subsequently found in Colorado, Texas, and Mexico; wurtzilite, in Utah.

An allied substance is ozocerite, or mineral wax, obtained in Galicia (Austria) and in Utah. (See under special heads.) For descriptions of the various deposits and theories regarding the origin of the asphaltic coals, the reader is referred to the following papers: Bailey and Ells, "Report on the Lower Carboniferous Belt of Albert and Westmoreland Counties, New Brunswick," in Geological Survey of Canada, Report of Progress, 1876-77 (Montreal, 1878); Peckham, "The Probable Origin of Albertite and Allied Minerals," American Journal of Science, Second Series, Vol. XLVIII. (New Haven. 1869); Lesley, "On an Asphaltic Coal Vein in West Virginia," American Philosophical Society, Proceedings, 1865 (Philadelphia, 1865); Wurtz, "On Grahamite," American Journal of Science, Second Series, Vol. XLII; Blake, "Uintahite, Albertite, etc.," Transactions of the American Institute of Mining Engineers, Vol. XVIII. (New York, 1890); Eldridge, "The Uintahite (Gilsonite) Deposits of Utah," Seventeenth Annual Report of the United States Geological Survey, Part I. (Washington, 1896); Taff, "An Albertite-like Asphalt in the Choctaw Nation,