134 CHEMICAL AGENTS IN DEFECATION. 
Scoffern asserts, it assists in the conversion of a portion of 
grape sugar into glucate and molassate of potash, which, 
like the product of the decomposition of grape sugar by 
lime, is to be preferred to a solution of grape sugar itself, 
being less viscid. The decomposition of organized sub. 
stances containing nitrogen also, is inferred to take place 
during the evaporation. 
After complete neutralization of the acid by the use of 
lime, the juice must be defecated or deprived of a number 
of substances which, if allowed to remain, would totally 
prevent the crystallization of the sugar, besides being pro- 
ductive of other injurious effects. I here recommend two 
methods for common use, giving the preference to that first 
mentioned only when its employment is indicated by certain 
favorable conditions described in Ch. XXX. It effects the 
separation of a very large amount of impurities, and particu- 
larly those which are the chief obstacles to crystallization. 
DEFECATION BY TANNIC ACID AND ALBUMEN. 
The peculiar advantage derived from the use of these 
substances consists in the removal of all glutinous, albu- 
minous, mucous, or gummy substances, together with all 
feculancies and other matters mechanically suspended in the 
juice, at the same instant, after heat has been applied, and 
they are firmly incorporated with the scum, which is not 
again permitted to remain in contact with the clarified 
juice. In the method of Wray, described in a subsequent 
page, one of these agents, tannic acid, is used ; but in that 
case it is necessary to add asecond dose of lime; the tannic 
compounds are suspended in the liquid, and are separable 
only by repeated filtrations, and much time is lost and much 
trouble incurred before the juice can be prepared for evap- 
oration. Besides, the clarification is by no means as per- 
