SUGAR. 271 



dium proportion ; and even then, that it 

 ought to be dissolved in boiling water, that 

 as little as possible may be precipitated. 

 The heat is suffered gradually to increase, 

 till it approaches within a few degrees of the 

 heat of boiling water, that the impurities 

 may be thoroughly separated. But if the 

 liquor was suffered to boil with violence, the 

 impurities would again incorporate with it. 

 It is known to be sufficiently heated when 

 the scum begins to rise in blisters, which 

 break into white froth, and appear generally 

 in about forty minutes. The fire is then 

 suddenly extinguished by means of a damper, 

 which excludes the external air, and the 

 liquor is allowed to remain about an hour 

 undisturbed, during which period the impu- 

 rities are collected in scum on the surface. 

 The juice is then drained off, either by a 

 syphon or a cock ; the scum being of a tena- 

 cious or gummy nature, does not flow out 

 with the liquor, but remains behind in the 

 clarifier. The liquid juice is conveyed from 

 the clarifier by a gutter into the evaporating 

 boiler, commonly termed the grand copper, 

 and, if it has been obtained from good canes, 

 it generally appears transparent. 



