METHOD OF USING ANIMAL CHARCOAL. 



107 



Some persons think it unnecessary to pass the liquor 

 through the charcoal filters, until it has been submitted to 

 the process of evaporation, and has acquired the density at 

 which it is proper to transfer it to the vacuum pan, or 

 otherwise finish the concentration at a low temperature; 

 but there can be no doubt it ought to be passed through 

 the charcoal on leaving the clarifier, after being first freed 

 from its insoluble impurities by calico filters, as otherwise 

 a loss is sustained during the process of evaporation, from 

 the scum thrown up, a portion of which consists of sugar, 

 combined with lime, which becomes gradually insoluble 

 from the increased heat to which it is exposed in the 

 evaporators, and is rejected as skimmings. 



By either of the plans proposed, the labour of skimming 

 during the process of evaporation is rendered unnecessary, 

 as the solution of sugar and water is nearly pure, and will 

 throw up no scum. It may be objected to the success of 

 the first process of defecation, without the use of animal 

 charcoal, that the separation of the albumen will not be 

 complete, as the very dilute state in which it exists in cane- 

 juice requires a greater degree of heat than 212° F. for its 

 perfect coagulation. This supposition is very doubtful, 

 but even if there should be any left in solution, after being 

 exposed to that temperature and to contact with infusion 

 of tannin, the quantity must be very small, and not likely 

 to be productive of injury. Many other methods of defe- 

 cation have been proposed as substitutes for the usual im- 

 perfect one. Dr. Evans describes nine different modes, 



