SUGAE.— Beet-root. Defecation. 895

turns a minute, while the cleansed roots are fed intothe hopper and are pressed up to the rasping face,either by their own weight or by a mechanicalarrangement which is not necessary to describe. Atthe same time a stream of water, equal in all to about50 per cent, of the weight of the roots rasped, isallowed to run on the face of the rasp, to assist in keep-ing the teeth clear, and to render the pulp more fluidand more readily pressed. The pulp being obtained,the juice is extracted from it either by pressing inwoollen cloths, by means of an ordinary hydraulicpress; or by feeding it into centrifugal machines,and when the greater part of the juice has beenspun out, giving a good washing with a measureddose of water; or lastly, by passing the pulp throughone of the so-called continuous presses.

In an article of this kind space fails to give ausefully-detailed description of the plant requiredfor each, or, indeed, any of these methods ; it musttherefore suffice to say that the continuous pressesconsist essentially of three or more rollers, some-what similar to an ordinary cane-crusliing mill,between which the pulp is fed by being carried onan endless band of cloth. In some of the manyforms of the machine one or more of the rollers areperforated, to facilitate the escape of the juice beforeit can be re-absorbed by the pulp when relievedof the pressure of the rollers. These continuouspresses extract less of the juice than the hydraulicpresses by about 3 to 5 per cent. ; but this is notlost where cattle are fed on the pulp, and the labourof many hands is saved. By re-rasping the pulpwith further addition of water, and passing it anewthrough a second press, a large proportion of theremaining juice is extracted in a diluted state, andcan be used in place of pure water on the rasp withfresh roots.

In this last case the yield of juice is almost equalto that obtained by the hydraulic presses, or about80 to 83 per cent, out of the 94 per cent, which theroots contain. The last and perhaps the best ofthe continuous presses is that of MM. Manueland SociN, which, with the extreme dimensions of7 by 13 feet, will press the pulp from 50 tons ofroots per day of twenty-four hours.

The second principal method of extraction—theso-called diffusion process — is employed verylargely in Austria and Eussia, where it is of theutmost importance to the manufacturer to extractthe greatest possible quantity of sugar from theroots, because he pays duty on the estimated weightof the latter, and obtains from his Governmentsuch a drawback on the export of the raw sugarthat each pound of sugar which he wins is worth tohim nearly twice its intrinsic value.

The roots are sliced up into strips, about half aninch broad and one-quarter thick by 2 to 4 incheslong, by help of a machine, which may be describedas an improved turnip slicer. The strips are thenfed into a series of iron cylinders, about 6 feet highand 4 feet diameter, furnished with a false bottomand two man-holes—one just over the false bottomand one at the top. These diffusers are so con-

nected together by pipes and valves, that the fluidcontents of any one of the series of six or more canbe forced on into any other by simply driving moreliquid into it. Suppose all to be filled with slicedroots except the last, and that cold (or slightlywarm) water is made to pass into the top of thefirst, and after filling it, out of the bottom to thetop of the second, and so on to the end of the series.During the stay of the first portion of water on thesliced root in the first diffuser it would receive acertain quantity of sugar by exosmose from thecells—indeed, if it stood long enough, the proportionof sugar to water would be the same inside andoutside the walls of those cells. This weak solutionof sugar would pass on to a fresh lot of root, andbecome stronger; and so on in each succeedingvessel. But the first diffuser would all this time bereceiving fresh quantities of water, so that by thetime the sugary liquid began to run from the lastof the series, the whole, or very nearly the whole,of the sugar would have been soaked out of thestrips in the first vessel. When this point has beenreached, the first vessel is disconnected from theseries, to be emptied and refilled with fresh-slicedroots; the second vessel then becomes the first toreceive the fresh water; while the spare vessel,which was not used at first, is brought into work atthe end of the series. In this way the freshest andleast-exhausted roots are always soaked in a solutionof sugar only a little less concentrated than theirown juice, while those which are nearly freed fromsugar find themselves in fresh water.

The extraction of juice by this method is veryperfect, and the product is comparatively pure,because the albuminous and gummy bodies asso-ciated with sugar in the juice of the beet are notcapable of diffusing with any rapidity through themembranous walls of the plant cells in which theyare confined. In this process the quantity of waterused is about two and a half times the weight ofthe roots; but as a very large proportion of thiswater remains in the exhausted slices, the dilutionof the juice is only about equal to 50 per cent. Theloss of sugar by imperfect extraction rarely exceeds05 per cent, of the weight of the roots.

Defecation .—The juice having been obtained byone or other of the above methods, is treated withan excess of lime, which ordinarily amounts to one-half to three-quarters per cent, of the weight of theroots operated on. This lime is added to the juice,heated to about 85° C. (185° Fahr.) in a copper pan,provided with a steam jacket. The admission of steamto the jacket is continued till the liquid is just on theboil, and beginning to break through the crust ofscum formed on its surface. The visible effect ofthis treatment is to change the dark, blackish-greenjuice to a clear light yellow. The real purifyingeffect is small as regards the separation of weigliablequantities of foreign bodies, but important as re-moving some of the most prejudicial, and so alteringothers that they are either rendered less noxiousor more easily removed at subsequent stages of themanufacture.