Concluding Remarks. Refined sugar (Saccharum—Ph. L., S. PURUM—Ph. E., S. PURIFICATUM—Ph. D.), raw sugar (S. COMMUNE—Ph. E.), and molasses or treacle (SACCHARI FÆX—Ph. L. & E.), were officinal.
The relative sweetening power of cane sugar is estimated at 100; that of pure grape sugar, at 60; that of fecula or starch sugar, at 30 to 40.
According to Messrs Oxland’s method (patented 1849) of defecating and bleaching the juice of beet-root, cane, &c., acetate of aluminium, formed by dissolving 4 lbs. of that earth in acetic acid, is boiled with each ton of sugar, and as soon as the acetic acid is nearly all driven off, a solution of tannin, formed from 1 lb. of bruised valonia and 2 galls. of hot water, is added to the boiling syrup; the excess of aluminium is afterwards separated by lime, and the usual method of further procedure adopted. By their second patent (1851), superphosphate of aluminium or of calcium is substituted for acetate of aluminium, in the proportion of about 6 lbs. of aluminium, dissolved in phosphoric acid, for each ton of sugar.
The presence of certain saline bodies in a solution of cane sugar, exercises a very prejudicial effect upon it, since these, by combining with the sugar, give rise to compounds which contribute to the more or less reduction of the sugar to the uncrystallisable condition, and to a consequent increase of the molasses.
Of one of the chief constituents of the sugar-cane that possesses this objectionable property is potash in combination with acids, both organic and inorganic. Last year a patent for the removal of these potash salts was taken out by the Messrs Newlands. The patentees proceed upon the facts that the solubility of alum in water is very trifling, and that it contains only 1⁄10th part of its weight of potash. They add to a concentrated syrup a strong solution of sulphate of alumina (having by a previous examination of the syrup determined the quantity required). Sulphate of potash is thereby formed, and this, uniting with the sulphate of alumina, the resulting alum after a time deposits in a crystalline form at the bottom of the vessel containing the sugar solution. This being run off into another receptacle, the free acid, of which it now contains a large quantity, is neutralised with lime or chalk, boiled, filtered, and passed through charcoal.
The addition of the lime has also thrown down the alumina liberated by the reaction, which has carried with it and removed certain injurious nitrogenous principles previously present in the saccharine liquid.
Some few years back Messrs Dubrunfaut
and Péligot being cognisant of the fact of the insolubility, in boiling water, of the compounds of sugar with lime, based upon it a method of separating crystallisable sugar from treacle. Péligot has obtained from common treacle one fourth of its weight of crystallised sugar, by dissolving the precipitated sugar lime in water, and separating the lime by passing into the mixture a stream of carbonic acid.
Sugar may be obtained from nearly all sweet vegetable substances, by a process essentially similar to that described above.
Table showing the Specific Weight of Sugar Solutions with the corresponding percentage of Cane Sugar at 17·5° C.—Gerlach.