896

SUGAR.— Beet-root. Defecation.

The clear, liighly-alkaline juice is drawn off frombelow the scum, and while still hot submitted tothe action of a stream of carbonic acid gas, obtainedeither from the burning of coke or charcoal, ordrawn from the top of a special lime kiln. Thecarbonic acid unites with the excess of lime left inthe defecated liquor, forming insoluble carbonateof lime, which, in precipitating, carries down withit some of the organic impurities of the juice as asort of “lake.” This “carbonation” is pushed so faras still to leave the juice slightly but distinctlyalkaline. The right point is marked by the readyseparation of the carbonate of lime in granularflocks; or in certain cases, is found by means of avery weak solution of an iron salt, from which ajuice which is still alkaline precipitates an oxide.The turbid liquid is then allowed to settle for some

time, and the clear portion run off from the sedi-ment, and either again limed and again carbonated,or passed straight to the charcoal filters after beingreheated. The sediment of carbonate of lime, to-gether with the juice mixed with it, is passed throughfilter presses, and the clear filtrate added to the restof the liquid. At the present time the defecationand carbonation are combined in one operation (pre-cede Jelineck , or carbonatation trouble') in a very largenumber of factories. Lime in considerable quantity(1'5 to 2'5 per cent, on the roots) is added to theslightly-warmed juice, and the stream of carbonicacid gas turned on, while the temperature is allowed torise at such a rate that a temperature of about 93° C.(200° Fahr.) is attained, at the same time that theelimination of the excess of lime becomes sufficientlycomplete. The whole mass of turbid liquid so

. mts s

produced is then forced through filter presses. Itis found that the total purifying effect of defecationand carbonation (saturation) is equal to the removalof about 40 per cent, of the soluble impuritiesoriginally present in the juice ; and as the alkalinesalts are not at all diminished, this purification mustmainly consist of the removal of the albuminousand gummy bodies.

The filter presses alluded to above have manyforms, but all consist essentially of a series of per-forated metal plates, covered with wire-gauze andcloth, and so arranged between movable frames ofwood or iron that the space between each two cloth-covered surfaces can be filled with the liquid to. befiltered under any desired pressure, while the clearliquid escapes on the other side, and is conductedinto a channel communicating with a reservoir.

Fig. 1 represents the arrangement of this filterpress. The lime scums from the purification of beetjuice are separated with great ease by this apparatusin the form of cakes, which only need to be againbroken up with water and dosed with carbonic acid,and passed again into a fresh filter press, to be almostentirely freed from adhering sugar. It is not toomuch to say, that without this most valuablepiece of apparatus the beet-root sugar industrywould never have attained its present perfection.The extreme convenience and rapidity of workingwhich it exhibits in the beet factory have naturallyinduced repeated trials of it for the purpose of clari-fying cane juice and the liquors of the refinery.These attempts have hitherto failed, the sliminessof cane juice and liquors from raw cane sugarcausing the filtering surfaces to become rapidly