Petroleum

Mineral oils of poorer quality are well adapted for lighter transmissions and rapidly running turbines.

For the working parts of fine machines, for instance the spindles of spinning machines, which make 8,000 to 10,000 revolutions per minute, and for looms, the selection of a good mineral oil is of the utmost importance. For the lubrication of spindles thickly-fluid and very viscous oils cannot be used; thinly-fluid and at the same time sufficiently viscous oils with a high flashing point being only suitable for the purpose.

The following summary of the properties of mineral oils is given in Spon's "Encyclopaedia of Arts:"

1. A mineral oil flashing below 300° F. is unsafe.

2. A mineral oil losing more than 5 per cent. in 10 hours at 60° or 70° F. is inadmissible, as the evaporation creates a gum, or leaves the bearing dry.

3. The most fluid oil that will remain in its place, fulfilling other conditions, is the best for all light bearings at high speeds. 4. The best oil is that which has the greatest adhesion to metallic surfaces and the least cohesion in its own particles; in this, fine mineral oil stands first, sperm oil second, neat's-foot oil third, and lard oil fourth; consequently the finest mineral oils are best for light bearings and high velocities. The best animal oil to give body to fine mineral oils is sperm oil. Lard oil and neat's-foot oil may replace sperm oil when greater tenacity is required.

5. The best mineral oil for steam cylinders is one having a density of 0.900 and a flashing point of 540° F., with burning point of about 600° F.

6. The best mineral oil for heavy machinery has a density of 0.890 and a flashing point of 360° F.

As previously mentioned, the distillates obtained from the residuum may be grouped according to their specific gravities and viscosities, the so-called solar or mixing oils being the lightest products obtained. The specific gravity of these oils varies between 0.860 and 0.890, according to their derivation. In consequence of their slight viscosity and low flashing

point they are not suitable for lubricating purposes, being employed only for small machinery, such as clocks, sewing machines, etc. Since these fractions form quantitatively the greater portion of the products obtained, provision must be made for their utilization. If their specific gravity is low enough, they are, in some cases, used as an addition to illuminating oils, and if pale enough and only slightly fluorescent, they are under the name of mixing oils added to vegetable oils to make the latter cheaper. They are also used as wool oils for preparing wool, as saturating oils in sugar houses, for the production of vaselines and pale wagon grease, and finally, in an unrefined state, for the production of oil-gas.

Of greater value, of course, are the heavy products of distillation, discussed above, which are used for lubricating purposes. Besides the general rules which govern the selection of a lubricating oil, it is also of interest to know the difference in the quality of mineral oils according to their derivation, in order to draw a conclusion as to their availability.

The cylinder oils embrace all the distillates boiling at a high temperature, while the machine oils include all other distillates, from the solar and mixed oils up to the cylinder oil.

The cylinder oils form a strictly defined group for one and the same purpose, while, on the other hand, the machine oils may be divided into various groups, they finding numerous applications.

As will be seen from the tables pp. 644 and 645 the specific gravities of Russian cylinder oils, which were examined by Künkler, rise from 0.911 to 0.923, and their flashing point from 188° to 238° C. (370.4° to 460.4° F.), and the specific gravities of machine oils of the same derivation from 0.893 to 0.970 and their flashing points from 138° to 197° C. (280.2° to 386.6° F.) The specific gravity of the American machine oils examined varies between 0.884 and 0.920, and their flashing point between 1870 and 206° C. (368.6° and 402.8° F.), and the specific gravity of American cylinder oils between 0.886 and 0.899, and their flashing point between 280° and 283° C. (536 and 541.4° F.).

If we now consider the conherence of the oils with regard to the purposes for which they are to be used, it will be seen that all oils serving the same purpose also possess approximately the same viscosities, and consequently that the viscosity is closely connected with the lubricating power. Thus the Russian spindle oils of 0.893 to 0.895 specific gravity show at 50° C. (122° F.) a viscosity of 3.15 to 3.44, and Russian machine oils of 0.903 to 0.909 specific gravity, at 100° C. (212° F.) a viscosity of 2.07 to 2.88. American spindle oils of 0.908 to 0.911 specific gravity possess a viscosity of 3.15 to 3.35, while the American cylinder oils of 0.966 to 0.889 specific gravity examined show at 100° C. (212° F.) a viscosity of 4.17 to 4.82.

These investigations show that, as regards flashing point and viscosity, American cylinder oils are far superior to the Russian, and on the other hand, that Russian machine and spindle oils surpass those of American origin.

It will further be seen from the tables, which also agree with the practice, that flashing point and viscosity are independent of each other, and that even very viscous oils may possess a low flashing point. The American oils congeal near o° C. (32° F.) with the separation of paraffine, while the Russian oils acquire an ointment-like consistency at -10° C. (+14° F.). American as well as Russian cylinder oils thicken sooner than machine oils.

The lighter Russian oils possess a bluish, and the American oils a greenish, fluorescence. American oils, almost without exception, are distinguished, as compared with Russian oils, by a better odor and taste, and greater purity of color. They also show less inclination to volatilization, and consequently are of greater constancy.

Regarding the properties of German oils, Engler finds that the Oelheim and older Alsace pit oils resemble Russian oils in so far that rising specific gravities correspond to rising viscosity and flashing point. The more recent Alsace oils, however, are distinguished from Russian oils by less viscosity if used for the same purpose, and by congealing at a higher temperature.

As regards viscosity the Oelheim pale oils are inferior to Russian, and about equal to American oils.