The Romance of Modern Chemistry

SUGAR AND STARCH is to immerse the canes in water and soak out the sugar. The juice obtained in this way is then concentrated to its crystallising point. The crystals are not pure, and are spoken of as “ raw ” sugar; the uncrystallisable juice which is separated from the crystals—uncrystallisable because of the mixture of substances which it contains— is used as food in the form of treacle or molasses. Although a good deal of raw cane sugar finds its way into the market as “Demarara,” the bulk of it is first refined. The process of refining consists in dis- solving the raw sugar in water, filtering the brown solution through cotton bags, and then decolorising it by keeping it in contact for some hours with animal charcoal. Contrary to what one might expect from the name, animal charcoal contains only one-tenth of its weight of carbon. It is got from bones in the same way as coke is obtained from coal, that is, by heating strongly in a retort. The organic matter in the bones is charred by this treatment, and the resulting carbon is distri- buted in a finely divided condition over the phosphate and carbonate of lime which constitute the bulk of the mass. In this state of fine division the carbon has the re- markable property of absorbing any colouring matter from a solution with which it is left in contact for a time. Red wine, for instance, if shaken with animal charcoal and then filtered, runs through as a colourless liquid, like water. A coloured sugar solution is similarly affected, and pure sugar is then obtained by concen- trating the decolorised liquid to the crystallising point, as already described. It is somewhat startling to reflect that a heap of uninviting-looking bones may be destined 230