CHAPTER XVII. 

 THE CONCENTRATION OP THE SYRTJP TO MASSECUITE. 



The juice after being treated in the multiple effect evaporator emerges as 

 a thick syrup of density about 1'25, and contains about 55 per cent, of solids 

 in solution. Before being passed on to the vacuum pan to be boiled to grain 

 it is sometimes subjected to a further treatment. This treatment may be 

 either mechanical or chemical ; when high class consumption sugars are being 

 made the syrup is sometimes sulphured or treated with phosphoric acid or other 

 decolourant ; this treatment is often combined with a filtration of the syrup in 

 sand filters or in the mechanical filters already described; in other factories 

 the only treatment that the syrup receives is that it is allowed to stand and to 

 deposit its suspended matter ; the practice of reheating the syrup in connec- 

 tion with steam economy schemes has been described in Chapter XYI. 



In the vacuum pan the syrup is further concentrated until it is a magma 

 of crystals of sugar and mother liquor ; the usual routine processes followed 

 are outlined below ; the magma of crystals of sugar and mother liquor is 

 known as massecuite. 



Processes followed. In the actual routine work the processes 

 followed to obtain the sugar in the juice are as below. 



1. Repeated Soilings. The syrup is boiled to a masse cuite and the cry- 

 stals separated from the mother liquor giving first sugar and first molasses ; 

 the first molasses are boiled into second massecuite and from this is obtained 

 second sugar and second molasses ; this process is carried on until fourth or 

 even fifth sugar is obtained after which the molasses are, or should be, 

 exhausted ; the number of operations required to obtain exhausted molasses 

 depends very largely on the initial purity of the juice ; the purer the juice the 

 purer being the first molasses and so on. The first massecuite may be cooled 

 before the crystals are separated from the mother liquor or it may be treated 

 direct from the pan ; if cooled, it may be cooled at rest or in motion. With 

 juices of purity 85 or over, the first molasses are generally pure enough to boil 

 to grain ; other first molasses, and in all cases second and subsequent molasses, 

 are boiled blank, '.<?., crystals are not formed in the pan but appear after the 

 mass has been struck out, and allowed to cool for a number of days. 



This scheme gives as many as four or even five grades of sugar and is 

 wasteful of time, fuel, and labour ; in addition, the third and fourth sugars 

 will often not be treated in the centrifugals for a whole year after they are 

 made, entailing an excessive floor space and the locking up of much money. 



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