pearing greenish in tint. The black oils in the United States are obtained from the Trenton limestone of Ohio and from California; the Pennsylvania oils are of amber tint. In addition to the hydrocarbons, which are the chief constituents of petroleum, the following substances may be present: Sulphur, nitrogen, hydrogen sulphide, carbon disulphide, arsenic, and phosphorus. The carbon percentage may vary from 79.5 to 88.7 per cent.; the hydrogen from 9.6 to 14.8 per cent.; the sulphur from 0.7 to 2 per cent., and in rare cases even 3 per cent.; nitrogen from 0.008 to 1.1 per cent. The hydrocarbons of all crude petroleums fall either into the paraffin or olefin group, those of America belonging chiefly to the first and those of Russia to the second group. The number of different members of the paraffin series present may be very large; some Pennsylvania oils, for example, have yielded 18 different paraffin compounds, as well as a number of substances belonging to the ethylene group. The hydrocarbons of the olefin series predominate in the Russian oils and many others. The composition of crude petroleum from a number of different localities is given below:
The Chemical Composition of Petroleum.
| LOCALITY | C | H | O | Specific gravity H2O = 1 |
| Per cent. | Per cent. | Per cent. | ||
| Heavy oil, West Virginia | 83.5 | 13.3 | 3.2 | .873 |
| Light oil, West Virginia | 84.3 | 14.1 | 1.6 | .8412 |
| Heavy oil, Pennsylvania | 84.9 | 13.7 | 1.04 | .886 |
| Light oil, Pennsylvania | 82.0 | 14.8 | 3.2 | .816 |
| Parma, Italy | 84.0 | 13.4 | 1.8 | .786 |
| Hanover, Germany | 80.4 | 12.7 | 6.9 | .892 |
| Galicia, Austria | 82.2 | 12.1 | 5.7 | .870 |
| Light oil, Baku, Russia | 86.3 | 13.6 | 0.1 | .884 |
| Heavy oil, Baku, Russia | 86.6 | 12.3 | 1.1 | .938 |
| Java | 87.1 | 12.0 | 0.9 | .923 |
| Beaumont, Texas | 86.8 | 13.2 | ...... | .920 |
The gravity of an oil is most commonly expressed in the degrees of the Baumé (B.) scale, on which water has a specific gravity of 10 degrees. The oils from Allegany County, N. Y., run from 38° to 41° B.; from Venango County, Pa., 46° to 48° B.; Warren County, Pa., 43° B.; Lima County, Ohio, 36° to 38° B.; Florence, Colo., 30° B. Russian oils average about 32° B. The lighter oils yield a better quantity of illuminants, while the heavier ones often serve well for lubricating purposes, etc. On exposure to the air many petroleums lose their more volatile constituents and change to a viscous or even solid condition resembling asphalt. The lighter colored varieties are often quite liquid, while the black or dark oils may be slightly viscous. The temperature at which crude petroleum solidifies ranges from 82° F. in some Burma oils to several degrees below zero in certain Italian oils. The flashing point may be equally low in the latter, but in others found on the Gold Coast it rises as high as 370° F. The boiling point likewise shows considerable variation, from 180° F. in some Pennsylvania oils to 338° F. in certain oils found at Hanover, Germany.
Distribution of Petroleum. The most noted and most productive field in the United States is the Appalachian, which extends along the western slope of the Appalachian Mountains, from southwestern New York (and eastern Ohio), through western Pennsylvania into West Virginia, Kentucky, and Tennessee. The oil-bearing sandstones are partly Devonian and partly Carboniferous, the latter being especially important in West Virginia. Four fields are recognized in Pennsylvania, the oil varying from amber to dark green. Ohio contains two districts. One of these, the Mecca-Belden field, is of minor importance; a second in eastern Ohio is a westward extension of the West Virginia area. The Lima-Indiana field extends from Lima southwestwardly into Indiana, lying without the Appalachian region as usually defined. The oil here is carried by the Trenton limestone of the Lower Silurian, the depth being about 1300 feet; it was first discovered near Findlay, Ohio. The oil is dark and heavy and resembles the Tennessee and Canada oils in its sulphur contents. Farther south oil is obtained from the Carboniferous in eastern Kentucky and in Tennessee. While new pools are discovered occasionally in the Eastern fields, the most important developments in recent years have been in the Southwestern and Western States.
Oil has been found at a number of localities in the Tertiary rocks of eastern Texas, and several fields, including the Corsicana, Nacogdoches, Beaumont, Elgin, San Antonio, and Sugar Lake, are now being exploited. The first mentioned supplies both light and heavy oils, which are obtained from depths of 950 and 1175 feet respectively. The first well put down in the Beaumont field yielded 75,000 barrels of oil a day, spouting the liquid in a six-inch column to a height of 160 feet; nine days elapsed before the flow was brought under control. The Beaumont oil is a dark asphaltic oil with much sulphur, and is obtained at a depth of 1000 feet. Petroleum has also been discovered in western Louisiana, especially near Jennings, where it is found at a depth of 1800 feet. Southeastern Kansas and northeastern Indian Territory produce some oil from the Cherokee shales and sandstones of the Carboniferous. In Wyoming petroleum occurs in 18 scattered fields, and in formations ranging from the Upper Carboniferous to the Upper Tertiary, but mostly in those of Mesozoic age. The Cretaceous sandstone at Florence, Colo., yields a heavy oil which resembles that of Wyoming in being valuable as a lubricant. Oil has also been obtained in moderate quantities at Boulder, Colo. It is obtained at depths of as much as 2850 feet, and has a gravity of 42.5° B. California contains several oil fields in the southern part of the State. The rocks are of Cretaceous to Neocene age. The oil has an asphaltic base, and is chiefly valuable as a fuel. Petroleum is also known to occur in Washington, Arizona, New Mexico, Montana, and Utah. A moderate amount of oil is obtained from Lambton County, Ontario, at a depth of 400 to 500 feet. Cuba is known to have at
