The Romance of Modern Chemistry

SUGAR AND STARCH wool—that is, cellulose—is treated with nitric acid, the explosive gun-cotton is obtained. If a weaker acid is employed, and the time during which it acts is shortened, another compound is produced, intermediate between cotton and gun-cotton. This product, when mixed with camphor and properly worked up, is celluloid. Although not explosive like gun-cotton, it is highly inflammable, and numerous burning accidents have been caused by the ignition of combs made of this material. Attempts have been made to render celluloid un- inflammable, but this can be done only by sacrificing some of its valuable properties. One of these is its plasticity; separate pieces of celluloid, when heated to a temperature a little above the boiling-point of water, can be welded together by pressure, just as two pieces of red-hot iron are welded under the blacksmith’s hammer. Then, again, celluloid can be planed, carved, or turned on the lathe, and the appearance of the articles so pro- duced leads to its name of “ artificial ivory.” It is em- ployed not only in combs, but in the manufacture of such various things as piano keys, billiard balls, dolls, and photographic films. At the beginning of this chapter carbohydrates were spoken of as important constituents of food, but it will now be evident that this important class of chemical com- pounds figures largely in common* life apart from food- stuffs. They are to be detected in our stationery, in our clothes, on our postage stamps, and indirectly in celluloid and the many useful articles which are made of this material. 236