802 SORGHUM. 



ordinarj defecation, or the defecator is at once emptied into a sub- 

 siding tank where the defecated juice is left until complete subsidence 

 is effected, when the juice is drawn off for evaporation as usual. 



Superphosphate of Lime. 

 The use of this compound has been very highly commended in defe- 

 cation. It is added in solution to the juice just before the neutrali- 

 zation with lime. The superphosphate of lime forms, with some of 

 the lime which is added in liming the juice, an insoluble phosphate 

 of lime, which is readily precipitated, carrying with it the lighter sedi- 

 ment which would the more slowly settle. As superphosphate of lime 

 of a high grade may now be readily obtained in the market, a solution of 

 it in Avater may be easily prepared for use. 



Alumina in Defecation. 



The use of alumina, either as the sulphate, phosphate, hydrate, or in 

 other forms, depends upon its property of forming, when precipitated 

 from its solutions, a gelatinous mass, which mechanically entangles the 

 impurities rendered insoluble by heat and lime, and in its subsidence 

 carrying such impurities along with it. Its use in clarifying water for 

 the purpose of the laundry, depends upon this same principle. 



The various forms in which it is used, are the sulphate (porous 

 alum so-called), and a mixture patented in England, over a half 

 century ago, known as " Howard's Finings," which, patented in 

 England, October 31st, 1812, by Edward Charles Howard, the in- 

 ventor of the Vacuum Pan, was largely used in the refining of sugar. 

 Similar mixtures are largely used in the United States. The ob- 

 jection to the use of alum is, that by it compounds of potash would 

 be introduced into tlie juice, the presence of which are very in- 

 jurious. 



Howard's Finings may be prepared, by boiling in a convenient vessel 

 thin cream of lime, until, after a few minutes, a sort of lime curd is 

 formed. Then, for each 100 gallons of juice, 2^ pounds of alum are 

 dissolved in 6 gallons of water, and 3 ounces of whiting, finely pul- 

 verized, is added to the alum solution, the mixture being stirred until 

 all effervescence ceases. It is then allowed to settle, and the clear 

 liquor is poured off. To the residue from Avhich the'liquor has been 

 drawn, enough of the curdy lime previously prepared is added, with 

 thorougli intermixture, until a slip of yellow turmeric paper is just 

 turned a slight brownish red when placed in the mixture. Then, after 

 letting the mixture settle and pouring off any supernatant liquid, it is 



