The oil is prepared for the market by a process of fractional distillation and relining of the frac tions with acid and alkali. The distillation prth.1.55 serves to separate the oil into three por tions, viz.: ( 1 ) Benzine distillate; (2) burning oils; (3) residuum. The first portion is redis tilled and yields very volatile produets (naph thas and gasolene's) that are used as solvents and for power in small engines. The second por tion is likewise redistilled nail yields two frac tions, which are treatt'd separately with strong sulphuric acid, followed by a washing with water, then t•catment with caustic soda. and st. final washing with water. By this process the oils are bleached and partly deodorized. The two oils are commonly known under the name of kerosene. If the distillation of the crude oil has been carried on by the vacuum process, in which the heavy vapors are withdrawn from the stills as soon as formed, 'cracking' dues not take place and the residuum may be used entirely tor preparing lubricating oils and vasdine. Dur ing the 'cracking,' is facilitated by heat ing the stills over free fires, the residuum is de composed and yields a further series of volatile products (chiefly used as burning oils). tug,the' with paraffin, lubricating oil, yellow 'wax,' and coke. Russian oils may be successfully treated by a continuous process of distillation, as they are not very susceptible to cracking. To guard against any possibility of change, the stills are heated by superheated steam. Oils containing large quantities of sulphur are very offensive and must be distilled over mixtures of oxides of cop per and lead to take up the sulphur, before they can be refined. The crude oil is, however, now largely used for fuel purposes with steam or compressed air in injector burners. The follow ing mineral oils are commercial articles: Petroleum Ether, distills over between 40° and 70' (2 (104° and 158' F.), and is used as a sol vent and for gas machines.
qasolcne, distills over between 70° and 90° C. and 194' F.), and is used as a solvent and for carbureting coal-gas.
Naphtha, distills over between 80° and 110° C. (176' and 230' F.), and is used far burning in vapor stoves, and as a solvent for resins.
Benzine. distills over between 120° and 1.50° C.
(24S' and 302° F.), and is used as a substitute for turpentine for cleaning clothing.
Kerosene. See article PETROLEUM.
Lubricating Oils, including spindle oils and cylinder oils. The analytical tests applied to these oils include determinations of specific gravity, the 'fire test' (i.e. determination of the flash-point and burning-point) , the cold test, and determinations of viscosity and neutrality. For burning oils the fire test and the determina tion of neutrality are the most important. For lubricating oil, the determination of viscosity is also essential. A large number of forms of ap paratus have been devised for obtaining the flash and burning point, but no other is as simple and reliable as the New York State 'closed tester.' This apparatus consists of a double boiler of copper heated by a gas or lamp flame, the inner chamber being, tilled with oil and covered with a glass plate perforated with two holes, one for the thermometer, the other for the introduc tion of the test flame. The oil must not be heated more rapidly or slowly than 2° F. per minute. At minute' intervals the test flame is brought to the hole in the glass (-over. A flash is said to occur when a blue flame momentarily plays over the surface of the heated oil, and at this point the thermometer is read. The burn ing-point, usually a few degrees higher, is that temperature at which the oil begins to burn.
Previous to the introduction of petroleum products, bituminous shale had been subjected to destruct ive distillation, yielding gas. ammonia. oil. and tar. This process is still carried out in Scotland, Germany, and various other European countries. Oil does not occur as such in bitumi nous shale. bumf is liberated by flue decomposition of the latter, which is a sort of pitch. Shale, in small pieces, is fed into vertical retorts 'heated to a low red heal, and steam is injeeted into the retorts to promote distillation. The vapors are condensed in a hydraulic main and scrubbers similar to those employed in the distillation of coal (see OAs, ILIA_ MIN.\ TING ), the ga,es given off being utilized fur heating the retorts. The crude oils are refined with acid and alkali, and are redistilled to furnish naphthas, burning and lubricating oils, and paraffin (q.v.).