47. The proportions of the various constituents of oils from the three districts are given in Tables VIII and IX, according to the commercial classification. In the Pennsylvania oil, only traces of rhigolene and chymogene are found, which, when exposed, evaporate almost at once.
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TABLE IX SAMPLE ANALYSES OF TEXAS AND CALIFORNIA OILS Texas Oil California Oil Distillate Per Cent. Distillate Per Cent. Naphtha and lighter oils Kerosene Residue 10.8 54.5 34.7 Gasoline Kerosene Middlings Lubricants Asphalt Residue 2.8 14.4 23.1 34.1 21.4 4.2
48. In its crude state, Texas oil is comparatively thick and heavy, and is used to a large extent, without refining, as a fuel under steam boilers or in locomotives. It is also used by mixing it with certain chemicals and compressing the mixture, under pressures of from 300 to 1,000 pounds per square inch, into small lumps or bricks, called briquets. When thus solidified, the heat value of the mixture is double that of the same weight of bituminous coal. An average heat value for the crude Texas oil. is 19,875 British thermal units per pound.
The crude oils of California, like those of Texas, have an asphalt base, but they have a larger percentage of illuminating oils and gasoline, and slight traces of paraffin are also sometimes found.
49. The relative proportions of the different compounds existing in petroleum have never been fully determined. Yet an approximate idea may be obtained by distilling
