The washer.— Passing over the stone-catcher, the beets are carried by the aid of an Arch imedean screw, or a beet wheel, up into the mechanical washer, where they are entirely freed of all remain ing dirt. This washer consists of a large tank in which arm-agitators revolve. As the beets have had most of their impurities removed in the hydraulic transportation from the sheds, the agitation in the washer renders excellent service in removing the particles that still adhere.
Slieing.—During the entire operation of washing, fresh water is being run in at one end and the dirty water out at the other. The beets enter the washer at one end and are thrown on an endless carrier at the other end and carried to the bucket elevator, which elevates them to the slicer several floors above. Here they are cut into strips, or slices as they are called, and emptied into the various cells of the diffusion battery for the extraction of the sugar which they contain.
The slicer.—In order that the greatest amount of surface may be exposed to the action of the water in the extraction of the sugar, it is necessary to cut the beets into long, slender strips, or cossettes, by the aid of knives made especially for this pur pose. These knives vary in shape as regards their cutting surfaces, but all types tend to secure one result, that of producing a long slender strip, cut lengthwise of the beet, and having a smooth, uni form surface. To secure this, a special apparatus is used which generally consists of a cylinder, or hopper, at the bottom of which is a circular disk with openings for knife attachments, and having a rotary motion. This is the slicer. The beets are fed into the hopper from the automatic scales, if these are used, otherwise directly from the beet elevator, and, falling on the knives, are cut into cossettes. These drop either from a spout into the cells of the battery direct or else on a moving belt conveyor, as in the case of a longitudinal battery, and from this are fed into the various cells as is necessary.
Diffusion batterg.—The diffusion battery consists of a series of ten to fourteen iron tanks, or cells, known as diffusors, which are arranged in a circle or in a straight line. Each diffusor is connected at the bottom by means of a pipe with the top of the next in the series, so that a continual flow of water passes through the mass of sliced beets as long as they remain in the cell of the battery. Their shape is that of a round tank set on end, which permits of the extraction of the sugar from the cassettes regardless of how they lie in the dif fusors, and at the same time does not retard the circulation of the juice. There are openings at the
top for filling the cells and at the bottom for emptying after the sugar has been extracted, tight fitting doors being used in all cases to close these openings. Near the bottom of each cell and above the opening of the pipe there is a screen of heavy sheet iron for the purpose of preventing the cas settes entering the juice as it leaves the diffusor, thus resulting in a stoppage of the pipe.
The principle of diffusion is based on the theory of osmosis, and, as sugar belongs to the category of crystaloids, the advantage of the diffusion pro cess over all others for the extraction of the sugar from the sugar-beet will be easily understood. Owing to the fact that a certain number of the cells in the beet become either broken or cut in the course of their passage through the slicer, thus allowing the contents of the cells other than sugar to pass into the juice, which would otherwise be absent, it will be seen why it is necessary to watch the knives and to take such precautions as will tend to keep them in the finest possible condi tion. Keyr estimates that about 6.41 per cent of all the cells of the beets are either crushed or torn in the slicing.
Care must he taken in the way the battery is worked, for, should the water remain too long in contact with the tissue of the beet, or reach too high a temperature, other impurities than those which pass into the juice from the broken cells would be absorbed by the water and produce trouble in the further treatment of the juice. The cell walls of the cossettes contain organic salts of lime and potash, and pectic compounds which be come dissolved under the influence of too high tem perature. As an example : Asparagine and gluta min, by heating in the presence of an alkali, are converted into apparetic and glutaminic acids, which, in the combination with alkalis, remain as salts in the juice ; by the above heating, ammonia is constantly given off, which tends to show a higher percentage of alkalinity than is really present. This interferes with the work at the car bonatation stations. The best working temperature of the battery is between 75° and 80° Centigrade, as above SO° there is a tendency for the pectine and the pectates to be absorbed from the cellulose of the beet, and this, as well as the high alkalinity at the carbonatation stations, tends to make the presses slimy and hard to wash. Frozen beets take an en tirely different temperature from those that are fresh from the field. The size of the slices as well as their thickness has an influence on the circula tion of the water through the cells if the tempera ture is not right.