D£F£CAX10>', PRINCIPLES OF. 287 



CHAPTER rX- 



(a.) Defecation, principles of. 



(6.) Defecation with lime. 



(c.) Other agents in defecation. 



{d.) Sulphurous acid and sulphites in defecation. 



(e.) Experiments in defecation. 



DEFECATION, PRINCIPLES OF. 



The juice extracted from the sorghum, or cane, by either of the 

 processes already described, is found to consist of a solution of not only 

 sugar, but of other soluble constituents of the cane which may be 

 present. Besides, the juice secured by the roller mill contains a 

 considerable portion of mechanical impurities, i. e., those which are 

 suspended in the juice as solid particles, and are visible to the eye, 

 often being in a state of subdivisioii so small tliat the effect of these 

 impurities may be only to render the juice turbid instead of clear, 

 as it should be when free from them. 



The juice obtained by the process of diffusion, is quite free from such 

 impurities, and is generally clear, containing only those substances 

 which are in solution with the sugar. 



The composition of the juice of sorghum, as obtained by the roller 

 mill, is given upon page 252. 



The production of sugar from the juice is accomplished by the re- 

 moval of the water and those constituents of the juice, wholly or in 

 part, which are present with the sugar. The more perfectly this is 

 done, the larger the amount of sugar which may be obtained from any 

 juice. 



Defecation, as the word implies, is the removal of impurities; and 

 from what has already been said, it is obviously the most important 

 operation in the manufacture of sugar. All the other operations are 

 mechanical merely. 



Defecation is both a mechanical and chemical problem, since the 

 impurities are both mechanical and chemical, and even the removal 

 of the latter is only possible, for the most part, after, by some means, 

 they have been converted into mechanical impurities. 



