OILS, FATS AND WAXES. The term "oils" is loosely used as a generic term for substances having the common property of being greasy fluids, either at the ordinary temperature, or at temperatures below the boiling-point of water. Formerly, when substances were principally classified by obvious characteristics, the word included such a body as "oil of vitriol" (sulphuric acid), which has, of course, nothing in common with what is now under stood under the term oils.
In its most comprehensive ordinary acceptation the word em braces at present the fluid, "fixed," or fatty oils (e.g., olive oil), the soft fats which may be fluid in their country of origin (e.g., coconut oil, palm oil), the hard fats (e.g., tallow), the still harder vegetable and animal waxes (e.g., carnaiiba wax, beeswax), the odoriferous ethereal (essential) oils and the fluid and solid volatile hydrocarbons—mineral hydrocarbons—found in nature or obtained from natural products by destructive distillation (petroleum, shale oils, oils from the low-temperature distillation of coal).
The importance of fatty and mineral oils to the life and industry of a nation is a commonplace of everyday observation; the exigencies arising from the World War did but emphasize human dependence on these raw materials for food and power, and stimulated development and research in all branches of the industries connected with them. Great advances have been made in the utilisation of mineral (petroleum) oils (q.v.). The last two decades have seen great developments in oil-fuelled internal combustion engines and the widespread adoption of oil as a fuel for steam-raising, both in stationary boilers and for shipping, and more especially for battleships, where high power output corn bined with economy in fuel-storage space and stokehold labour are of primary importance. Improvements in the production of lubricating oils have been necessitated by the advances in modern machinery, which involve higher working temperatures and pres sures. We may note in passing the development, especialiy ire Germany, probably as a direct result of war-time isolation from supplies of mineral oils, of the production of oils by the distilla tion of lignites and by synthesis from producer gas.
The fatty oils, ever of paramount importance as food, acquired an increased significance during the War as sources of glycerine, the basis of explosives of the dynamite class. In England, strict
government supervision was exercised over soap manufacture, and all industries involving the hydrolysis of fats, to ensure the maximum recovery of glycerine (about 10-14% of the weight of a fresh oil). Towards the end of the War period a process was mooted to replace the glycerol in edible fats by mannitol or a similar sugar, in order to obtain both the glycerine and a product equal in nutritive value to the original fat.
The shortage of edible oils in all countries during the War led to great advances in the technique of oil-refining; oils hitherto regarded as purely industrial became available for food as a result of improved methods of purification, and it may be said that to-day almost all fats, with the exception of those possessing marked physiological action, such as castor, curcas and chaul moogra oils, can be utilised as food. Especially in the Central European countries, where, as a result of the blockade, the short age of fats became acute, every effort was made to stimulate the investigation and production of synthetic fats. In some cases pro cesses were put into actual operation ; and in Germany attempts were made to supplement available resources with fat obtained from yeast under intensive cultivation. Synthetic fatty acids can be prepared by the oxidation of paraffin wax and other hydro carbons, and glycerides have been synthesised on the large scale by heating these acids, under pressure, with glycerol, which may be obtained by the fermentation of non-crystallisable sugars. In view, however, of the enormous expansion of which the natural production of the fats is capable, it is extremely improbable that these methods will be commercially successful under normal economic conditions.
The common characteristic of all the "oils" is that they consist principally, in some cases exclusively, of compounds of carbon and hydrogen. They are all readily inflammable and are prac tically insoluble in water. The mineral hydrocarbons found in nature, or obtained by destructive distillation do not come within the range of this article (see NAPHTHA, PARAFFIN, PETROLEUM), which is restricted to the following two large groups of bodies, formed naturally within the vegetable and animal organisms, viz. (I) Fixed oils, fats and waxes, and (2) Essential, ethereal or volatile oils.