The Romance of Modern Chemistry

FATS AND OILS place when a newly washed cloth is hung out on the clothes-line. In the latter case simple evaporation of water, a purely physical process, takes place, while the drying of paint involves a chemical change, the com- bination of the oil with oxygen from the air. Like the painter, the glazier depends on the drying qualities of linseed oil when he fixes up a new pane of glass with putty. This dough-like material is obtained by grinding up whiting with linseed oil, and it is the latter ingredient which is responsible for the gradual hardening of the mixture on exposure to air. This curious drying power of linseed oil is made to contribute to the equipment of our houses, not only in paint, but also in linoleum. Linseed oil is the raw material of the linoleum manufacture, and the first operation in the factory is the drying of the oil on a large scale; this is effected by hanging up sheets of textile material and allowing the oil to run slowly over them; under these circumstances it dries gradually to a tough, gelatinous mass. This oxidised and solidi- fied linseed oil is then mixed with rosin and ground cork, spread on a canvas backing and sent into the market as linoleum. One purpose for which drying oils are obviously not suited is lubrication. If linseed oil were put into the bearings of a machine, it would get viscous and tough in the manner already described, and the running of the machinery would be hindered instead of helped. For lubricating purposes a non-drying oil is required, such as tallow oil, lard oil, neat's-foot oil, olive oil, rape oil, or castor oil. The metallic variety of palm oil, which travellers frequently find necessary to stimu- late official activity or to produce temporary blindness