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Page:Popular Science Monthly Volume 35.djvu/220

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THE POPULAR SCIENCE MONTHLY.

from impurity. With, the mere washing of the beets the sugar manufacturer is not content; they are therefore freed from those parts which are poor in saccharine, damaged or otherwise undesirable, by a machine called a carousal.

When cleaned, the beets are thrown from the wash-barrel into a hopper, from which they pass into an endless elevator which carries them to the top floor, where they are discharged-into a large hopper. They then pass into a cage which will hold one thousand pounds of beets, and, when this weight is indicated, the cage empties its load into the cutter or slicer. Fig. 5. The cage and the indicator enable the factory people to closely estimate the amount of raw material used each day. It is also a check on every department. It will show any error that may arise in the receiving or shipping departments. The slicer is a round iron shaft, rotating horizontally, and fitted with steel knives capable of slicing four hundred tons of beets in twenty-four hours. The rotating knives, which, descend upon the beets, cut them into thin slices, thus exposing the sugar-cells, which is an important factor in the diffusion system. The lower end of the cutter opens into a wooden trough about two feet square, on the bottom of which is an endless belt. As the sliced beets fall from the cutter, the belt carries them along to the diffusion tanks.

In alluding to the operation of the diffusion battery in the article on Growth of the Beet-Sugar Industry," it was said that "though simple in its conception, it nevertheless illustrates well known laws of chemical science in the transfusion of liquids, and successfully opens the membranous walls of the sugar-cells of the plant, giving a higher grade of juice, with less gummy, nitrogenous, and fibrous impurities, at less cost than by the old methods of mechanical pressure." By membranous diffusion is understood the process of exchange between two fluids of unequal density, contained in two vessels separated only by a membrane. Supposing the sugar-cells to be brought in contact with pure water, then, theoretically, if the cells contain twelve per cent of sugar, transfusion will go on till an equal weight of water contains six per cent of sugar, while by the passage of water into the cells the juice there is reduced to the same degree. Taking the six-per-cent watery solution and treating with it fresh roots containing twelve per cent of sugar, a nine-per-cent solution will be obtained, which, on being brought a third time in contact with fresh roots, would be raised to a density of 10ยท5 per cent. Thus, seven eighths of the whole sugar would be obtained at the third operation, and it is on this theory that the diffusion process is based.

A diffusion battery, Fig. 6, consists of a range of twelve large, close, upright cylinders called diffusers, provided with man-holes above and perforated false bottoms, with a like number of heaters.