When crude petroleum is subjected to distillation and the uncondensable gases and moisture have gone over, a series of light hydrocarbon compounds known as "benzine" are first obtained, about 15 per cent. Then a number of grades of burning oil, known as "distillates," come over and are collected separately. They are treated and bleached and freed from adhering scorched impurities with sulphuric acid and solutions of caustic soda. From 50 to 60 per cent of these oils is obtained and the remaining residuum oil forms the basis for the petroleum lubricating oils.

The lighter products of the distillation, the crude benzine, are subjected to redistillation with steam heat and are separated into their respective degrees of specific gravity and characteristics required by the manifold demands for their use. They are purified, deodorized and bleached by treatment with chemicals and are sold as naphtha, gasoline, benzine, and under many fancy names.

The "distillates," which are next obtained, are likewise purified and bleached by treatment with sulphuric acid and solution of caustic soda and by exposure in bright and shallow tanks to the bleaching influence of sunlight. Numerous grades of distillates are produced by being carefully separated from each other during distillation.

The proceeds of distillation at specific gravities are the benzine series, from the highest gravity (the first distillate obtained) down to about 56° to 58°, standard white or export oil of 110° F. flash or 70° Abel test, from 56° to 54° and then from 42° to 39°. Water-white oil, 120° flash or 150° fire test, the legal test of Ohio and now the generally accepted test of most states, from 54° to 46°, or until the distillate begins to show color. Prime white oil, 150° fire test, from 46° to 42°, and headlight oil, 175° fire test, from 46° to 39°.

In case 110° standard white and 175° headlight oils are not desired, there will be but two separations between 56° and 39°, viz., 150° water-white oil and 150° prime white oil, the necessary fire test being obtained by driving off the lighter vapors by redistillation in a steam still, or by steaming and spraying in an agitator or open tank, but preferably in a steam still, in which case what is known as a "Straight Run" (distillate from 58° to 46°) water-white oil, the requirement of almost any State law as to flash or fire test, can be made. These gravity separations are not absolute, but flexible within a few degrees, dependent upon the nature of the crude oil used and the grade of oil desired.

The continued distillations from 39° down to 29° constitute the neutral distillates, and are divided by separation into what is known as 300° F. or mineral seal oil and 34° to 36° neutrals, or by redistillation into a small percentage of prime white or headlight, 300° or mineral seal, 34° to If the distillation from the crude still is carried from 29° to 20° and the product afterwards redistilled, the residual of the second distillation will be the commercial red oils of high viscosity and gravity of from 30° to 23°.

The residual oil in the crude still at 24° to 19° is usually pumped hot into a tar-still and the distillation continued down to coke, producing the paraffine distillates hereafter to be described.

The carbonaceous residuum or coke left in the still is used in the manufacture of carbons for electric lighting.

The neutral oils are purified and bleached by treatment with sulphuric acid and solution of caustic soda. They are deodorized by air-blast and their fluorescence skillfully removed with chemicals. They are largely used for adulterating the more costly animal and vegetable "fatty oils."

The crude paraffine oils hold crystalline paraffine wax in suspension, produced by the disintegration of hydrocarbon compounds during the process of distillation. It is extracted from the oil by freezing and pressure, and is purified by treatment with sulphuric acid and caustic soda while being kept in a liquid state by heat. It is bleached with benzine and then cast into solid blocks.

Paraffine wax is largely used in waterproofing fabrics, for insulating, and in the manufacture of candles and matches, and numerous other products. The paraffine oil left after separation from the wax is treated with acid and solution of caustic soda and is filtered through animal charcoal. It is used for lubricating and is known as "Golden Machine Oil." The paraffine oils of varied degrees of specific gravity form the basis for many engine lubricating oils and are compounded with fatty oils in endless proportions.

In order to make the residuum oil left in the still, after distilling off the burning oils, directly useful for the purpose of lubricating engine cylinders, the oil is put into tall vessels, surrounded by steam, and the impurities, produced by the scorching influence on the oil against the heated bottom and sides of the still during the process of distillation, are allowed to settle. This kind of residual is sold under the name of " Steam Refined Cylinder Oil."

Crude oil of proper character will also produce a good cylinder oil by introducing steam during distillation in the bottom of the still, sufficient to prevent scorching or carbonizing by running down to 23° to 27° in the still. The lower the gravity the higher the fire test. If run slowly and carefully and strained while hot, a second steaming and settling will not be necessary to produce a good steam-refined cylinder oil.

Crude oil not suited for cylinder oil produces a black lubricating oil or "West Virginia oil," as it is sometimes erroneously called.

Residuum oil is also filtered, while hot, through animal charcoal, to give it a brighter color and deprive it of all charred impurities held in suspension. As such it is known in the market as "filtered cylinder stock." Repeated filtration produces the products well known under the names of " vaseline," " cosmoline," " petrolatum," and many other fancy names. They are all compounds of paraffine wax in an amorphous state, to which the original crystalline wax of the residuum oil has been converted by chemical action during the repeated filtering through animal charcoal.

Petroleum Oils For Lubricating

Petroleum oils for lubricating should have a flash point above 300° F. On general principles, the most fluid oil that will stay in place should be used ; the oil that possesses the greatest adhesion and the least cohesion is the best. These conditions are possessed first by the petroleum oils and second by sperm oil, neatsfoot oil, and lard oil. For light pressure and high-speed machinery, mineral oils of a specific gravity of 30° Baume and 350°

F. flash point, mixed with sperm oil, olive oil or rape oil, are used. For ordinary machinery, oil of a specific gravity of 25° to 29° Baume, with a flash point of 350° to 400°F., mixed with lard oil, neatsfoot, tallow, or with vegetable oils is used. For use on spindles in cotton mills, oils of 360° are quite safe, and the flash point for cylinder oil should not be below 500° F.

For gas engines and gasoline engines, a pure hydrocarbon oil of high vaporizing point, about 260° F., a flash point of 430° F. and a fire test of 550° F., is considered best.

A compound of lard oil and petroleum burning oil, used in lanterns as signal oil, should not contain less than 40 per cent of prime lard oil and have a flashing point not below 200° F., and a burning point or fire test not above 300° F.

Uses Of Petroleum

Petroleum is one of the greatest gifts bestowed by nature on mankind. Gasoline derived from petroleum oil enables us to travel in automobiles, with airships and motor boats. The burning oil from petroleum supplies light and heat to the humblest cottage. The lubricating oils derived from it lubricate the endless number of machines used in industrial working, and enables us to travel by steam and electric power over land and water. The neutral oils and the paraffin oils are utilized in the manufacture of the "Valve-Oleum" oils, well known as mineral castor oils and mineral gelatines, and the many grades of vaseline are used to give medical relief to suffering mankind.

The "Dieterichs Kafer-Oil Liniment" and the carbolated "Kafer-Ointment," two reliable household remedies in use for many years and recommended by thousands, are products of petroleum compounds.

The paraffin wax derived from petroleum oil serves for saturating paper, for water-proofing, and in ironing fabrics, for covering to protect canned fruits, for insulating electric currents and for many other uses.

The residuum oils left from the distillation of petroleum oils and the heavier natural ground oils are used as fuel oil for heating steam boilers and stills in place of coal.

Coke, the last of the products from petroleum oils, is utilized for the manufacture of carbon candles, for electric lamps and many other electrical appliances.

Deblooming Petroleum Oils

For adulterating animal or vegetable fatty oils with petroleum, neutral oils are debloomed, which means freeing them from their fluorescent appearance, by refining them with chromic acid, or more readily as follows :

The oil is heated to about 140° to 160° F., and nitro-naphthaline, binitro-benzol or binitro-toluol, known as myrbane oil, is added and well stirred into the oil in proportions of about three ounces to from twenty to twenty-five gallons of oil with a slight bloom, and from fifteen to twenty ounces for oil with heavier bloom. No material influence is thereby exerted on the the oil and no tendency of the bloom to reappear remains.

For test, boil one part of the oil with three parts of a ten per cent solution of potassium hydrate in alcohol for one or two minutes. If either of the nitro-compounds is present, a blood or violet-red coloration will be produced. A pure oil is changed by this test to a yellow color only.

Deodorizing Petrol Oil

Kerosene oil and benzine can be freed from their bad odor as follows:

The kerosene oil is mixed with chloride of zinc and then poured into a vessel which contains burnt lime, and after stirring well, is left standing for some time, to settle, when the pure kerosene is drawn off.

The benzine is mixed and well stirred with a mixture composed of alkali manganese oxide, some water and sulphuric acid. After some twenty-four hours' standing the benzine is drawn off again, treated with permanganate and soda in water.

Benzine and kerosene oil can also be deodorized and bleached, and their specific gravities improved, by a treatment with nascent or fixed hydrogen gas. One per cent of amylacetate will also deodorize petroleum oils.