11. Mineral Oils have of late years taken immense strides in the popular and merited estimation of consumers, for general lubricating purposes. Their application in horology will be discussed in another part of this volume. They are obtained from the residuum of petroleum distillation, and vary so greatly in their properties that many of them are not applicable to delicate mechanism; but as the lighter varieties seem to fulfill all the necessary conditions, the writer will here consider their source and method of treatment.
12. Petroleums are obtained from many different localities, being fluid, bituminous oils, all having the same general characteristics and origin. They are all hydrocarbons, and contain little or no oxygen. As their origin is thoroughly discussed in many works on that subject, and as there is such a diversity of opinion regarding it, the reader is referred to such works.[3]
13. Paraffine, both liquid and solid, is obtained by the distillation of crude petroleum by means of superheated steam. When the heavier hydrocarbons begin to come over the receiver is changed and the butyraceous distillate is filtered through a long column of well dried animal charcoal. The first portion of the percolate is colorless or nearly so.
The distillate is made water white by some refiners by an acid treatment, followed by a water-and-alkali washing. On exposing this mass to a low temperature it becomes thick, somewhat like "cosmoline" but white. (59.) It is then shoveled into cotton bags of very strong material and subjected to powerful pressure by means of a hydraulic press. This operation divides the paraffine into two parts: the solid paraffine wax from which candles, etc., are made remaining in the bags, while that which is expressed is paraffine oil. If the operation is carefully performed the oil will be free from crystaline paraffine at a very low temperature.
Fig. 5.—Extracting Oil from the Head of a Porpoise.
14. Neutral Oils[4] "are refined paraffine oils varying in specific gravity from 0.8641 to 0.8333. For the purpose for which these oils are employed it is especially necessary that they be thoroughly deodorized. They are largely used for the purpose of mixing with animal and vegetable oils. It is said that a mixture of 95 per cent of a good neutral oil of the right gravity, and 5 per cent of sperm oil, has been sold for pure sperm. Ordinary inspection as to the odor and general appearance would fail to detect the adulteration. Having been subjected to the usual process for the extraction of crystaline paraffine, they will stand a very low cold test, and having been passed through bone black cylinders, they are free from odor and have but little color. They are usually exposed for a few days in open shallow tanks for the purpose of removing the flurescence of petroleum oils. Unmixed with heavier oils they are too light in body (especially the lighter varieties) to be employed as spindle or machinery oils, but when mixed with such oils in the proper proportions they form admirable lubricating compounds for general lubricating purposes when very high speed is not required." (70-71.)
Fig. 6.—Rendering Room in D. C. Stull's Factory.