CHAPTER XIX 

 Sugar Boiling and Crystalization-in-Motion. 



After concentration in the multiple effect the juice emerges as a thick sjTup, 

 containing from 50 to 70 per cent, of gra\'ity solids. The actual density 

 obtained is controlled by the caprice of the executive, by the capacity of the 

 evaporators, by the purity of the juice, and by the type of sugar that is being 

 made. Considered from the standpoint of fuel economy, as high a densit}' as 

 possible should be obtained. Sugar boilers, however, find difficult}- in main- 

 taining an even regular grain when the sjnrup is delivered to them at too high 

 a densit}', since in this case the sugar deposits so rapidly that the successive 

 charges do not have tim.e to mix thoroughly with the contents of the pan 

 before granulation occurs. There should, however, be no difficulty in handling 

 syrups at 60° Brix, and this density may be regarded as standard in Cuba. 

 With the extremely pure juices obtained in Hawaii from the Lahaina cane, 

 svTups up to 70° Brix are treated, 65° Brix bemg the average with the less 

 pure juice from Yellow Caledonia cane. It should be noted that as the purity 

 increases, the difference between gravity solids or Brix and absolute solids 

 decreases, and herein lies the possibility of working at so high a Brix N\ith the 

 purer juices. 



In making 96 test sugar, the syrup usually undergoes no treatment other 

 than being allowed to casually stand in the supply tanks as stock in process. 

 A certain amount of settling takes place here, the bottoms being diluted and 

 run back to the scum tanks as may be convenient. The dirt that is found here 

 is partly due to inefficient settling of the juice and parti}' to matter that has 

 become insoluble on concentration. To the presence of suspended matter 

 trouble in boiling and in dr^dng the massecuites may often be traced. 



When making white sugar, the syrup is allowed to settle and to deposit 

 its suspended matter or else is filtered in stocking, leaf, or plate and frame 

 presses. For satisfactory subsidence concentration to not more than 50° Brix. 

 is necessar}^, whereby the consumption of steam is much increased. Filtration 

 is also Hmited by concentration, the rate falling rapidlv at concentrations above 

 60° Brix. 



Algebraical Theory of Sugar Boiling. — The whole process of, and principles 

 involved in, sugar boiling can be explained on a very simple algebraical reason- 

 ing. Starting with a S3Tup, the continued removal of water by evaporation 

 allows a point to be reached at which the water is insufficient to keep all the 

 sugar in solution, which then begins to crystallize out. If the S3T:up consisted 

 of sugar and water only, the complete removal of the latter would afford a 

 complete recovery of the former in a dry and pure state. Since, however, 

 bodies other than sugar are present, some water must be left in the magma 



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