CHAPTER XVIII. 
PROCESS OF MANUFACTURE (CONTINUED). 
Drainage—In what it consists—Mode of Working—Extent to 
which the Production of the Higher Grades of Sugar may profit- 
ably be carried in Draining Vessels—Sugar Moulds—Descrip- 
. tion of the Process of Natural Drainage and the Mode of pre- 
paring White Sugar—Reboiling and Crystallization—Summary 
of Conditions necessary to Success in Liquoring Sugars—Sep- 
aration of the Molasses by Mechanical Pressure and Other 
Means—The Centrifugal Drainer. 
NATURAL drainage does not remove all the molasses in 
contact with the crystals of sugar, and hence sugars pre- 
pared by that mode are always more or less impure. Mo- 
lasses is hygroscopic, or attracts moisture from the air; 
_hence the sugar becomes more or less moist and ‘“ heavy.” 
The crystals are always in some degree colored, because of 
the molasses which coats them, and fills the interstices, and 
for the same reason they have not the pure sweet taste of 
white sugar. 
The purification of sugar is effected by simply washing 
the crystals with a liquid that is capable of expelling or 
taking the place of the molasses without dissolving the 
sugar. This liquid is syrup of greater purity than that 
which is to be expelled or washed out. It is poured over 
the top of the mass of impure sugar contained in a vessel 
which admits of drainage, and is carried down by the force 
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