Page:The New International Encyclopædia 1st ed. v. 15.djvu/754

PETROLEUM. least small supplies of oil, and a limited quantity has been exported from Porto Rico. In Mexico active exploration has been carried on at several points in the Gulf Coast region with the result of finding supplies of good oil around Tampico. It has an asphalt base. Of the South American countries, Peru is the most important petroleum producer, most of the output coming from the Zorritos field. Petroleum is also said to occur in Venezuela, Argentina, and Ecuador, but it is not taken out of the ground to any extent.

Russia is not only the most important foreign producer of petroleum, but the largest producer in the world, the fields in the Baku region of Southeastern Russia supplying enormous quantities annually. The greater part of the output comes from the Baku field proper, although important quantities are obtained from the Grosni field, 500 miles north of Baku. Rumania contains several promising oil fields, which occur in the same formations as the Russian fields. In Germany oil is obtained near Hanover, and also in Alsace, while some is supplied by the Carboniferous rocks of Great Britain, but does not begin to supply the local demand. In Japan petroleum is obtained on the northwestern coast, and some of it is refined. The crude material sometimes yields 60 per cent. of illuminating and lubricating oils. A high paraffin oil is found in Java, and Sumatra, Borneo, and the Burma field of India are important producers. While petroleum is known to occur in the Philippines, little is obtained, and that by primitive methods; the islands of Panay, Leyte. Guimaras, Negros, Bohol, Mindanao, and Cebú all carry some petroleum.

The modern method of drilling for petroleum is similar to that used in sinking gas and artesian wells. The most prominent feature of the oil-drilling outfit is the derrick, which is a tall, pyramid-like wooden frame about 75 feet high, 12 feet square at the base and about 3 feet at the top. The cost of a rig, as it is called, ranges from $200 to $275. The diameter of the well hole is 10 or 12 inches at the surface, decreasing with depth to 5 or 6 inches. In Russia wells are drilled of much greater diameter, and 26 inches is not an unusual size for the beginning of the bore-hole. In many cases the oil does not flow when the oil-bearing rock is struck, and it is customary in this instance to explode a torpedo at the bottom of the drill-hole, whereupon the oil almost immediately begins to pour out of the well, sometimes with tremendous velocity. For details of petroleum mining, see. The question of cheap and rapid transportation of crude petroleum from the wells to the refineries is one of great importance. At first the oil was transported on carts, later it was carried in barges or by railway in tank cars, but these methods gave place to the system of pipe lines. At the present day the total length of pipe lines transporting Pennsylvania crude oil is probably over 25,000 miles. The pipes, which have a diameter of from 4 to 8 inches, are usually laid underground and have bends at regular intervals to allow for contraction and expansion. Stations with pumps and storage tanks are placed from 28 to 30 miles apart, the oil being received into the tank at one pumping station and then forced through the pipe to the next one. Since all petroleum contains more or less paraffin or wax, much trouble is often experienced in the clogging

of the pipes, especially in cold weather, and to clear them out an instrument known as the ‘go-devil’ is sent through the pipe. This is so constructed that it is forced along by the moving current of oil and scrapes the paraffin oil from the inside of the tube. Pipe lines have been built from the Appalachian oil region to Jersey City, Philadelphia, Baltimore, Chicago, and Cleveland.

The refining of petroleum is based upon the separation of the component hydrocarbons by a process of fractional distillation. This is usually carried out in horizontal cylindrical iron stills, which are surmounted by a dome that connects with a vapor pipe. A common size of still is 30 feet long by 12½ feet in diameter, with a capacity of from 650 to 700 barrels of crude oil. When the latter is placed in the still and subjected to increasing temperature, the oils pass off in the order of their volatility; the separation is not absolutely perfect, however, as oils of lower boiling point may carry over some higher ones. As the vapor rises it passes to the condenser, a series of iron pipes surrounded by cold water. The distillates are led off into their respective tanks. This process of distillation, which is known as the intermittent system, is the one commonly followed in the United States, and the still requires periodic refilling. In Russia a continuous system is employed, involving a series of stills, which are heated to successively higher temperatures. The crude oil then flows slowly from one to the other, and from each one there passes off the product volatilizing at the temperature to which the still is heated.

The process of fractional distillation can be divided into two parts. In the first part of the process the more volatile products, such as gasoline and other naphthas, are evolved. The residue is then transferred to another still in which the second part of the operation is carried on, the oil being heated to a still higher temperature for the purpose of separating the illuminating and lubricating oils. The condensing apparatus ends in the tail house, where the distillates are conducted to their proper tanks. When the various fractions of the distillation are to be kept separate, and of constant composition, a special form of condenser may be used, by means of which the oil is brought into contact with the surface of iron turnings, thereby increasing the evaporation. If the oil contains sulphur it is necessary to redistil it in stills containing copper oxide, which removes the sulphur. Cracking is a term used to denote the process of condensing the heavier vapors in the still, causing them to become superheated and decomposed, and thus obtaining a more complete separation of the fractions, as well as increasing the percentage of illuminating oil. In the distillation of the oil the lightest constituents pass off first and the heaviest last. The fractions obtained in the order of their lightness are the following: Cymogene. This is the lightest of all, and since its boiling point is 32° F., it is a gas at ordinary temperatures. Rhigolene. Boiling point, 65° F. Petroleum ether. A highly volatile product having a specific gravity of 0.635. It has sometimes been called Sherwood oil. Gasoline. This, properly speaking, is the fraction following petroleum ether, although the name is often applied to a mixture of this and the three previous ones, its gravity thus ranging from 0.635 to 0.690. In