4. The clear oil from the second stage of the process, after being washed, is heated by steam to 176° F., mixed with 10 per cent. of its weight of granular animal charcoal, and then allowed to rest to permit the animal charcoal to subside.

5. After the latter is separated, the liquid portion is filtered through filters heated by steam.

6. The residue is subjected to hydraulic pressure, the expressed oil filtered, and the solid portion again used in the next operation, a sufficient quantity of fresh animal charcoal being added to make up for any loss or waste.

Second process. The raw materials, residuum or mineral tar, are rendered fluid, and the liquid, after the separation of all extraneous matters, is passed through a series of charcoal filters such as are used in sugar refineries.

After passing through twelve to fifteen of these cylindrical filters, the original brownish-black color of the liquid has become wine-yellow. To render it colorless and limpid as water, double the number of filters are required. The liquid acquires a lower specific gravity the more discolored it becomes, but when it has become colorless the specific gravity remains stationary, no matter how long filtration may be continued. After it has thus been freed from all bituminous matter, it is transferred to the "duplicator" where it is brought in direct contact with superheated steam, and the temperature is allowed to rise to 480° F. Samples taken occasionally from the boiler should show no changes in the product after this temperature has been kept up for a few hours. The finished vaseline, amounting to about 25 or 30 per cent. of the raw material, is finally filtered and filled into cans for shipment.

A great drawback in this method is the rapid exhaustion of the animal charcoal, which is able to decolorize only a small percentage of its own weight of crude vaseline. It is, therefore, necessary to provide extensive facilities for extracting the portion of vaseline retained by the charcoal and to regenerate the latter, which may be done by superheated steam at a temperature of 752° to 932° F. It is for this reason that most facto

ries use sulphuric acid for purifying, by means of which the raw material may be brought to the color of beer, so that only about one-third as much charcoal is required for final decoloration. It is, however, almost impossible to get rid of the last traces of the chemicals employed, and for this reason the quality of the vaseline obtained by the other process is much superior. It is pure white, like the best tallow, and entirely tasteless. It is also odorless, not only when rubbed upon the hand, but also when melted in water; the latter property distinguishing it from all other varieties, which, on melting in water, evolve a faint odor of petroleum. When melted, it yields a clear colorless liquid which, on cooling, returns to its former homogeneous condition. Cold 98 per cent. alcohol dissolves, on shaking, 2.2 per cent. of vaseline. The residue left after the evaporation of the alcohol is liquid at ordinary temperatures. Hot alcohol dissolves it completely to a clear solution. On cooling, the vaseline separates in flakes. It behaves in the same manner towards benzol and ether, but is not completely soluble in the latter even on warming. It does not impart an acid reaction to water, and is not affected by solution of potassa. Boiling sulphuric acid of 1.600 specific gravity and boiling nitric acid of 1.185 specific gravity have no effect on it. Fuming nitric acid colors it yellowish-red and sulphuric acid of 1.820 grayishblack. The acid itself acquires a yellowish-brown color. The specific gravity of the vaseline is 0.848.

Saponification of Petroleum Products.

The fact that petroleum absorbs oxygen has already been discussed in the chapter on "Manufacture" and only the industrial application of this property needs here to be mentioned. E. Schaal has endeavored to convert petroleum into acids by treating it in the presence of alkaline reagents with a current of air. Hydrocarbons boiling between 3020 and 752° F., together with a few per cent. of a finely pulverized mixture

* German patent No. 32705.

of lime and caustic soda, are heated to the boiling point in a boiler a, Fig. 257, provided with a back-flow condenser. A current of air or oxygen is then blown in, more alkali is gradually added, and the soap formed drawn off at C. The same object is said to be attained by bringing the hydrocarbons with about 20 per cent. of caustic alkalies, or alkaline carbonates, or other alkaline mixtures, in connection with oxygen-conveying

substances (copper salts, etc.) in a fine state of division, into intimate contact with the air. Many hydrocarbons readily oxidize with chloride of lime, and others not at all. When the action of the chloride of lime is complete, the lime is removed by hydrochloric acid, the acids formed are extracted with alkali, and the oil-mixture remaining behind is treated for a few hours longer with soda lye at 392° to 572° F. The fatty acids formed may be separated by distillation in vacuum. The most volatile acids yield, especially wlth methyl, ethyl, propyl, butyl, amyl and other alcohols, sweet-scented ethers for perfuming purposes. The acids boiling at higher temperatures form with glycerin combinations resembling natural oils, while the acids boiling at the highest temperature yield soaps and fats. It is also claimed that the sulpho-combinations of these acids, which

are obtained by slightly heating with one-half or equal portions of sulphuric acid, may be used for Turkey-red dyeing. By treating petroleum distillates with soda lye, oxygenated hydrocarbons are withdrawn, which in the presence of soaps and alcohol may also be converted into water-soluble combinations. Engler and Bock also found that petroleum contains saponifiable naphthalene-carbonic acids, while Zaloziecky supposes them to be the hydrocarbons of the methane series, which can readily be converted into acids.

A distinction has to be made between this oxidizing property of the hydrocarbons and their saponification with fats, the latter consisting simply in an intimate mixture of the hydrocarbons with sebates. This process is well known, the production of wagon grease and consistent lubricants for which mineral oil is used being based upon it.

A novelty in this process is the use of sebates, which, when melted, are capable of absorbing large quantities of mineral oil. Prof. Dittmar of Glasgow succeeded in preparing such a mixture which contained but a few per cent. of such sebates as cementing material. The fact that mineral oil could be made consistent in so simple a manner led to the most extravagant expectations, such as solid petroleum which could be readily transported, etc. Such expectations, however, have not been

fulfilled.

The so-called naphtha candles have also proved useless. The mode of preparing them in the factory of K. L. Miller, in St. Petersburg, has not progressed beyond the experimental stage. Petroleum with fats or fatty acids which are boiled with water of ammonia or ammoniacal salts is used, or ammonia gas is introduced into a solution of fatty acids in petroleum. Candles prepared from this mass have the defect of the petroleum vaporizing from them, thus imparting to them a disagreeable odor and bad appearance. Coating with varnish (amber or copal varnish) produced only a temporary effect, the varnish being gradually dissolved in the oil. It has also been endeavored to give the surface a better appearance by the addition of resin

and wax. According to statements emanating from the factory the candles are prepared from 65 per cent. stearic acid, 30 per cent. petroleum, 5 per cent. water, and about 0.8 per cent. ammonia. An analysis by the Technological Institute of St. Petersburg, however, gave only a content of 10 to 12 per cent. petroleum, and 82 to 85 per cent. stearic acid, 41⁄2 to 5 per cent. water and 0.6 to 0.75 per cent. ammonia, the candles having thus lost in the course of a month the greater portion of their petroleum. By being further exposed to the air for 45 days they lost 10 per cent. in weight. Photometric examinations were rendered difficult by the fact that the candles burn with a very flickering flame and the separation of much carbon on the wick. The illuminating power of a candle (four to the pound) was found to be equal to 1.05 standard candles with a consumption of 10.5 grammes (162 grains) per hour.

The use of fats for lubricating purposes, if not rendered necessary by special conditions, must under all circumstances be designated as unsuitable. The advantage of a slight consumption of material is nullified by greater friction and consequent greater consumption of fuel, as well as increased expense in repairing bearings, etc. The loss by friction alone counterbalances the greater consumption of liquid oils. A consistent fat answers the intended purpose only when it becomes fluid, i. e. when the lubricated portions of the engine become heated to or above the melting point of the fat. This increase in the temperature can be attained only by friction of the metallic surfaces, and greater expense of power, consequently greater consumption of fuel is required to overcome these resistances. Hence for lubricating machines, transmissions, etc., all fats should be rejected. It is different in the lubrication of cylinders and slide valves, for which purpose neutral fats may be used. Lubrication with tallow is absolutely to be excluded.

Consistent fats, especially the so-called rosin-soaps, which consist of lime soaps of rosin-oil in connection with petroleum distillates of less value or residuum, are used as wagon grease, etc. Their preparation does not come with in the scope of this work, and the reader is referred to books on that subject.