The Romance of Modern Chemistry

FATS AND OILS signals being still fed with rape oil. In lighthouses, too, there is a certain extent of adherence to the old kinds of burning oil, inasmuch as whale and seal oil are largely employed in the lamps; it is true these are animal oils, in contrast to olive and rape oils, but they belong to the same class of chemical compounds. Fats and oils are made available for illuminating purposes not only directly, in the way just described, but indirectly also, after being subjected to chemical treatment by the manufacturer, and being made to yield up the fatty acids which they contain in com- bination with glycerine. In connection with the subject of lubrication it was said that under the influence of high-pressure steam a fatty oil might be decom- posed into fatty acid and glycerine. Now, although this may be undesirable behaviour in the case of a lubricant, yet it is precisely the change which the manu- facturer brings about on a large scale in order to pro- duce candles. Our forefathers, it is true, used unchanged fats in the manufacture of candles ; we have all heard of “ tallow dips,” and the “ snuffers ” which went along with them. Tallow is the rendered fat of cattle and sheep, and con- sists chiefly of two fatty acid glycerides, those of stearic and oleic acids, together with a small quantity of the glyceride of palmitic acid. The mixture is easily melted, and the “ dip ” was made by repeatedly dipping a cotton wick in molten tallow. The wick in a modem candle, on the other hand, is made of yarn, plaited in such a way that the end of the wick bends over and is burned at the side of the flame, as the reader has doubtless observed himself. Such a wick cannot be employed in a tallow candle, 244