WRAY’S METHOD. 157 
chanical means which are of wider application, and more 
generally understood. Defecation requires the use of such 
chemical agents, and mechanical appliances, as will cause 
the separation of the impurities from the juice without im- 
pairing the quality of the sugar—a substance which in 
such association is remarkably unstable, and liable to be 
either injured or totally destroyed. It should be men- 
tioned also that there are many beautiful methods known 
to the chemist, and extremely useful and successful in the 
laboratory, which,-on account of the expense, complexity 
in the use of the means employed, or for other reasons, are 
totally inapplicable on the larger scale in practice. With 
these at present we have nothing to do. 
WRAY’S METHOD 
first deserves attention, as it was originally brought into 
notice in connection with the earliest attempt to make 
sugar from sorghum in thiscountry. At the first view the 
merits of this process are obvious. Throughout, it is 
simple and easily understood... It consists in treating 
sorghum juice—previously neutralized by lime—with a 
solution of nut-galls (tannin), which has the property of 
precipitating in an insoluble form from the juice of ripe 
cane, nearly all the impurities which hinder the crystalliza- 
tion and drainage of the sugar. Tannin, or tannic acid, 
the active agent used, is an abundant natural product, and, 
as has been already mentioned, may be obtained in a suffi- 
ciently pure and inexpensive form for ordinary use. The 
defecation is begun and finished in the cold juice, and the 
detrimental effects of successive reheatings are entirely 
avoided, and the evaporation may be carried on expedi- 
tiously to the close without any interruption. These are 
important considerations. I will add to them by saying, 
14 
