SUGAE. 



175 



the bottom of the clarifier, the impurities remain behind, and are 

 thoroughly separated. Bisulphite of lime is now commonly used 

 with the same object as sulphurous acid gas. It is added in solution 

 as soon as possible after the juice leaves the crushing rolls. 



In making inferior kinds of sugar, the clarified juice is run into 

 a battery of open pans, called " taiches," the whole apparatus being 

 styled a " copper wall." These pans are heated by direct fire under 

 them, and the juice, as it concentrates, is ladled from one pan to the 

 other, being skimmed all the time, and finished at last in the pan 

 farthest away from the furnace. The whole operation is " messy," 

 and extravagant in fuel. An improvement on the copper wall is the 

 " concretor," a shallow tray set over a furnace, down which the juice 

 runs in a thin stream, and is rapidly concentrated ; but in this appa- 

 ratus, also, on account of the steam from the juice being wasted, the 

 expenditure of fuel is very great. For the higher classes of sugar 

 the clarified juice is run through bag filters, and afterwards through 

 animal charcoal, or through the latter only, and concentrated in the 

 manner above described, or by means of double-action or treble-action 

 tubular concentrators. At Bene Mazar four sets of treble-action con- 

 centrators are used. Each set consists of three vessels. The first set 

 is heated by the waste steam from the various steam engines. The 

 steam evolved from the juice in these boils the syrup in the second 

 set of vessels, and in like manner the steam produced in the second 

 set boils the syrup in the last set of vessels. The first set works at 

 about the pressure of the atmosphere, the second set at a partial 

 vacuum of ten inches, and the third set, like vacuum pans, under a 

 vacuum of about twenty-six inches. After concentration, and for the 

 higher classes of sugar, the syrup, at about 22° Beaume, is again 

 passed through charcoal filters, and then boiled to grain in vacuum 

 pans. Inferior sugars are struck either directly from the last " taiche 

 of the copper wall, or from some one of a numerous array of tubular 

 and other granulators, working at the ordinary atmospheric pressure. 

 The molasses is now almost universally separated from the crystal- 

 lized sugar by means of centrifugal machines. There is great diffi- 

 culty in getting the juice and syrups to pass through animal charcoal 

 of sufficient fineness to produce much effect. The animal charcoal 

 used by refiners, for example, is about as fine as No. 1 shot, while 

 that used in Egypt is as coarse as hazel nuts, and even then it clogs 

 very quickly. It appears that, until the molasses has been in a 

 great measure separated from the crystallized sugar — which is only 

 to be done in the curing room — the syrups cannot be made to filter 

 efficiently, and that, for this reason alone, it is well to avoid charcoal 

 filtration. It is certain that juice is degraded by passing over large 

 surfaces, as it thereby has a tendency to get sour, and thus to in- 

 crease the percentage of molasses. It is hardly necessary to remark 

 that the first cost of the charcoal, the daily waste, and the charges 

 for fuel and labour in reburning, are serious items in the account. 



A valuable contribution to the ' Chemistry and Physics of Sugar 

 Manufacture ' was also given in the foregoing paper by Mr, George 

 Ogston, analytical chemist, in the following terms : 



