BITUMEN, the name applied by the Romans to the various types of natural hydrocarbons, the word petroleum not being used in classical Latin. Classical and Biblical references to bitu men are of frequent occurrence. In Genesis xi. 3 we are told that "slime had they for morter" and in Genesis xiv. i o that the vale of Siddim "was full of slimepits," the word slime in the latter quotation appearing as bitumen in the Vulgate.
In the modem use of the word, largely owing to its commercial application, there is a tendency to restrict its popular meaning to the solid or semi-solid hydrocarbons, although in its widest sense it includes all the natural hydrocarbons. In the classification now generally accepted, but not, as yet, established by authority, gaseous hydrocarbons are, however, excluded.
The solid bitumens are characterized by being fusible and largely soluble in carbon disulphide. Allied to, but distinct from the bitumens are the Pyrobitumens, a group of solid substances characterized by being infusible and insoluble, but which, on heat ing, generate or become transformed into bodies resembling bitu mens in their solubility and physical properties.
In its various forms bitumen is one of the most widely distrib uted of substances. It occurs, though sometimes only in small quantities, in almost every part of the globe and throughout the whole range of geological strata, from the Laurentian rocks to the most recent members of the Quaternary Period. All the asphalts, asphaltites, and asphaltic pyrobitumens, with the excep tion of oil shale, have probably been derived from liquid petro leum, either by the evaporation of the lighter fraction under atmospheric conditions or by deeper seated metamorphism. A range of products similar to many of the native solid bitumens is obtained as residues on the distillation of various types of crude petroleum, these forming many of the "asphalts" and "bitumens" of commerce. (See ASPHALT.) (J. R.) See Herbert Abraham, Asphalts and Allied Substances (New York, 1918) ; Percy E. Spielmann, Bituminous Substances (Berne, 1925) .