Osmosis.—The osmosis process is based on the same principles as the diffusion method for extracting beet- and cane-juices (see pp. 1842-5), the salts contained in the molasses diffusing much more rapidly through a porous diaphragm than sugar. The difference of time is, however, insufficient to enable direct separation to be made. At the commencement of the operation, the membrane is traversed by much salts and little sugar, whilst later on, the reverse takes place; the operation is, therefore, interrupted when 2% part of the salts is extracted, so enabling a part of the sugar to be crystallized by evaporation. The second molasses separated from the crystals is of the same composition as the first ; this is again diffused, and the operation is repeated until the product is too impure to be worked further. The process is inexpensive, but it causes a loss of nitrogenous matters and potash salts, and it is difficult iu some cases to get rid of the washings, which arc apt to contain deleterious matters.
The " osmogene '' employed in the process is shown in Figs. 1328 aud 1329. It consists of two chambers, separated by a suitable diaphragm. One chamber contaius molasses, while the other is filled with ordinary water, the two being parted by a septum of parchment-paper. Each com partmeut is a wooden frame 39 in. wide, 26 in. deep, and about in. thick ; 4 wooden stays divide the interior of the frame into 5 compartments, communicating by openings. On each face of the frame, are fitted leaves of parchment-paper, held up by:thin cords. The molasses, entering at the bottom, rises in a serpentine into the 5 compartments of the frame, and escapes at the top. A second similar frame, filled with water, is placed in juxtaposition to the first, so that the same sheet of parchment-paper serves to separate the two frames, and consequently the two liquids. This constitutes one " element " (coupie): several such placed in rotation form the complete osmogene. Circulation is established by channels in the frames, one at the left, below, com municating only with the molasses frames, the other, above on the right, for the circulation of water. The frames are screwed together by long bolts ; they usually number 50, sometimes 100. To change the tapes, the screws are undone, and the frames laid on a table. The molasses enters at a temperature of 60°-75° (140°467° F.), and the water at 85° (185° F.); the density of the molasaus is reduced from 41° B. to 30° or 25° B. It might be atill further lowered, with corresponding mat in evaporation.
A modification of the osrnogene, introdneed by Lilpop, Ran, and LOwenstein, of Warsaw, takes the form of Trinks' filter-press. The frames, to the number of 51, rest by mum of projections
upon two horizontal arms, and aro screwed together. The discharge of the apparatus and change of liquids is facilitated by arranging the whole t,o rotate on its axis.
Elution.—In thin process, the sugar of the molasses is converted into tribasie suemte of lime, by mixing the molasses with about a quarter of its weight of lime, when the mass solidifies ; it is treated with water, which removes the organic matters, while the suerate of lime remains solid. This latter is carbonated (like lime juice), and gives a syrup of 23° B., containing 33.7 per cent. of sugar, and 5.7 of impurities. Much sugar is lost in the washing-water ; it has been proposed to remedy this by washing with alcohol of 37^, instead of water. The loss is then much less, and the exosinosis waters con tain for I00 parts sugar 131 parts of total im purities. The former process is due to Lair et Bilange ; the latter has been named " elution " by Dr. Seheibler.
Seyferth has modified the elution method by using molasses at 43°-44° B. at a tetnpera ture of 30°-33° (86°-91i° F.), filtered through a perforated plate to remove foreign matters. Then 30-40 per cent. of quiek-lime,—free from clay, dry, and very finely powdered,—is made into a cream with water, and added to the molasses in little vats. The mass heats to 125° (257° F.); the water evaporates, and swells the bulk or 4-fold. At the same time, ammonia is disengaged, in the propor tion of 2.35 parts of steam for 0.008 parte of ammonia, per 100 of molasses. During the swelling-up, the mass is btirred, to prevent it running over. When the operation is finished, the whole is cooled. The vat is opened, and the cake is broken into froginenta the size of a nut, without making any powder. These fragments are regularly supplied to lurge " elutors," having the form of diffusors, arrauged in a battery, and surmounted by an outlet-tnbe for the displaced air, which tube plunges into a sort of condenser for the purpose of retainiug the alcohol disengaged with the game. Alcohol of 35 per cent. is introduced int,o the elutors from below, and remains for 12 bolus upon the lime mixture. It is then drawn off, and replaced by another charge for a further 12 hours. This latter, being but slightly charged, eorves for the maceration of a fresh quantity of lime mixture. Tbe suerete is thus treated 5 or 6 times, till at last it is quite white and pure. At this moment, steam is injeeted int,o the elutor. The alcohol which remained imprisoned in the inmate distils, while the suerate itself is reduced to a paste, and ean be readily drawn off.