THE CLARIFICATION OE DEFECATION OF THE JUICE. 



Effect of Alkalies on Reducing Sugar. The action of large 

 quantities of alkalies on reducing sugars is discussed in the next chapter. As 

 shown originally by Lobry de Bruyn and van Ekenstein 4 , reducing sugars, 

 when heated with small quantities of alkalies, suffer isomeric change ; depen- 

 dent on the conditions of experiment, dextrose and levulose are mutually 

 convertible into each other ; in addition, mannose, and a sugar to which the 

 name glutose 5 has been given, are also formed. Mannose is formed in only 

 small quantity, but the prolonged action of alkalies on the naturally 

 present reducing sugars of the cane results in the 

 formation of considerable quantities of glutose ; this 

 body is unfermentable, its reducing power is half 

 that of invert sugar, and it may account for the 

 unfermentable reducing residue found after fer- 

 menting molasses with yeast. In cane juices the 

 dextrose is always in excess of the levulose, but 

 in molasses due to this isomeric change a reversal 

 of this order may happen. 



This isomeric change also takes place under 

 the influence of the alkali salts of weak acids, such 

 as sodium acetate. 



The Use of Sulphur. After lime the 

 agent that has been most used in clarification, and 

 one the real effect of which is but little known, 

 is sulphur, in the form of sulphurous acid or 

 sulphur dioxide. Various apparatus are in use for 

 impregnating juices with sulphurous acid, of which 

 three forms are illustrated below. 



The ' sulphuring ' is often performed in the 

 apparatus shown in Fig. Ij^.. It consists in general 

 of an upright vertical chamber, about twelve feet 

 high, constructed of wood. At every foot or so 

 horizontal perforated plates 0, or some other device 

 calculated to throw the juice into a shower, are 

 fitted. The sulphur fumes enter the box at the 

 bottom, being led by the pipe c from the oven where the sulphur is 

 burnt. The juice enters the sulphur box at the top of b, and falling down 

 in a fine shower passes out at d. An upward draught is created in the 

 sulphur box by allowing a jet of steam to exhaust through the pipe . 



In Fig. 145 is given a view of a more detailed scheme ; an air compressor 

 or pump b forces the air necessary for combustion first through the vessel d,' 

 packed with quicklime, and thence to the ovens a. The rate at which the 

 sulphur burns is controlled by the speed of the pump or compressor. Above a 



FIG 144. 



247 



