petroleum

[ Lat.petra =a rock, and oleum =oil.] Chem. Earth oil, naphtha, mineral oil, paraffin oil. A term applied to a variety of inflammable liquids found naturally in many parts of the earth, and formed by the gradual decomposition of vege table matter beneath the surface. These liquids vary in color from a faint yellow to a brownish black, and in consistence from a thin transparent oil to a fluid as thick as treacle, and their specific gravities range from '7-1'1. They are met with in most countries of Europe, but occur in abundance in Pennsylvania and other parts of the United States, and in Canada. Pelouze and Cohours have shown that these oils consist mainly of homologues of marsh-gas, and they were able to isolate by fractional distillation twelve members of the series [PARAFFIN, 1 (2)], gaseous, liquid, and semi-solid. A light petroleum oil is used all over the world for illuminating purposes, and a heavy oil for lubricating machinery. IMG:content-0961.png:[blocks in formation] IMG:content-0962.png:[blocks in formation] Chem.: The portion of petroleum which distills stock against the over between 120° and 170°. Specific gravity, 740 to 745. It does not di olve resin, and is used for diluting linseed oil varnishes, and for cleaning printers' type. petroleum-spring, s. Geol .: A spring consisting of, or largely impregnated with, petroleum. They are often found in connection with mud volcanoes. petroleum-still, s . A still for separating the hydrocarbon products from crude petroleum, ., in the order of their volatility. petroleum-tester, s . An instrument for determining the inflammability of illuminating oils, or of inflammable matter in compound liquids, by means of a thermometer and a flame, the thermometer being applied to the liquid while the heat is imparted to the latter, and the vapor generated by the heat being directed to the flame, so as to take fire when the heat rises to the point at which the liquid gives off explosive vapors.