The Romance of Modern Chemistry

FATS AND OILS grounds, the natives will have nothing to do with animal fat of any description, vegetable butter is prepared in large quantities from cocoa-nut oil and palm-nut oil. The Greenlander, on the other hand, who has no such scruples, revels in blubber. The preparation of edible butters and oils is only one of the many industries which depend on the utilisation of fats and oils. If it were not for their disguise, for the chemical processes to which they have been subjected, we should detect these materials in many an unsuspected place. They may be traced not only in the butter on our bread, but also in the candles which light our tables, on the artist’s canvas, in the linoleum on our floors, and in the “matchless cleansers” which delight the house- wife’s heart. The chemical processes which have been referred to as disguising the obvious characteristics of fats and oils are not all carried out by the manufacturer. There is one class of oils, the so-called “drying” oils, the value of which is due actually to their own instability and to their sensitiveness to atmospheric influences. Common linseed oil, obtained from the seeds of the flax plant, is the typical member of this class. If a film of linseed oil is exposed to air it absorbs oxygen with great avidity, becoming gradually more and more sticky and viscous during the absorption, until at last it dries to an elastic skin. The amount of oxygen thus absorbed by the oil may be as much as twenty per cent, of its weight In this respect linseed oil is abso- lutely different from, say, olive oil, which remains liquid however long it is exposed to the air, and is therefore described as a “ non-drying11 oil. The complete drying of a thin layer of linseed oil 240