Treatment of the Lime Scums.The scums collected in the lime defecation process contain, in the fresh state, sugar, numerous nitrogenous matters, and other fertilizing elements. Plicque, workiug upon scums having the composition : Water .. .52.70 per cent. Organio matter .. 9.24 per cent.
Sugar .. .. 3 50 Phosph ates .. 4 77 Nitrogenous matter .. 3.72 Lime, silica, iron, &e. .. 26.07 obtained the following products, estimated on the dry weight : Animal black 50.0 per cent. Alcohol at 85° 2 0 per cent.
Lime .. .. 35 . 5 Sulphate of ammonia 1.0-2.0 The excess of moisture is removed from the " green' scums by the use of ffiter-presses. The scums of the two carbonations are collected in the same cistern, fitted with two monte-jus. The escape-pipes from these monte-jus re unite into one, so that though the monte-jus are used alternately, there is no fluctuation in the supply of scum to the fil ter-presses. The systems most largely used are those of Trinks, and Durieux et Roettger.
Trinks' press, Fig. 1313, is com posed of a series of cloth bags, held against metallic plates pierced with holes. The monte-jus forces the dirty liquid into these bags; the juice runs away clear, while each bag fills with the solid scum, which is strongly com -pressed by the steam in the monte-jus. When the bags are full, the juice no longer escapes ; then, to remove the superfluous moisture from the scum, steam alone is forced in. The steam condenses and washes the scum, dissolving the last traces of sugar, and yielding a slightly saccharine liquor. The action of the steam is continued until, having forced a passage, it escapes at the lower part of the apparatus. Steam is then shut off, and the operation is con cluded. To enable the bags to be opened easily, they are formed of two quadrangular cloths put together, the four borders of which are pinched, two and two, between wrought or cast-iron frames, presenting an opening only for the passage of the scum and steam. The frame, and consequently the set of cloths forming bags, are separated by metallic plates, which permit the juices to escape ; these juices run along the plates, and collect in a gutter closed by a tap, with screws to regulate the speed of the outlet, and even to suspend the working of a cloth, when it is torn for instance, without stopping the whole press.
Farinaux's press is composed of plates analogous to those of Trinks. In the upper part of the frames are two hearers, on which is screwed a wrought-iron stirrup. A horizontal traverse is fastened to one side of the fixed frame, and passes through all the stirrups, supporting the frames. The advantages claimed for it are that it is easy to adjust all the frames to the same height, and that the dismounting and replacing of the frames is much easier. According to another plan of Farinaux's, tho working of the press is rendered largely mechanical, so that ono labourer out of two is dispensed with. The bags are made of sail-cloth, and last 24-30 days, while those of jute endure only 5-8 days.
Durieux et Roettger's press is shown in Figs.1314 and 1315. Numerous other forms might be specified, but their effect is practioally the same.
Ammonium phosphate Process.A process was invented some years ago by Lagrange, chemist at the refinery of Guions, Paris, for separating the calcium and magnesium salts, with which beet sugar is especially liable to he contaminated (see analyses p. 1846). The object of the process is to throw down the calcium and magnesium as tribasio phosphates, by the addition of tribasic ammonium phosphate, (NR,) 3PO to the syrup. Much, sometimes nearly the whole, of these earthy salts, exists as sulphates, though portions are usually chlorides or nitrates. The salts of tho earthy bases retard the crystallization of the sugar, with varying effect according to the particular metals they may contain ; and the acids, especially if they be mineral acids, with which the earthy metals are in combination, likewise possess specific powers of their own in retarding the crystalli zation of more or less sugar. Sulphuric acid would appear to be tbe most powerful, while phosphoric acid seems to exert little if any influence ; small quantities of ammonium phosphate are indeed stated to rather favour crystallization. Lagrange's process simply and ingeniously contrives to get rid of tbe calcium and magnesium, and, by the same operation, to precipitate and extract any sulphuric acid present.