MANUAL FOR SUGAR GROWERS. 97 



monia ; and thus five hundredweight will be worth 

 about twenty shillings, or fully four pounds per ton, 

 if used direct as manure. 



What scum-cake is produced in excess of what 

 the stock can eat should be ploughed into the soil 

 at the rate of about five hundredweight per acre, or 

 sold if a profitable market can be found. 



The quantity produced will be roughly half a 

 hundi'edweight per hogshead of sugar made. It 

 will thus be seen that no estate can afford to be 

 without a filter-press, and it is somewhat surprising 

 to notice how slowly proprietors have placed them 

 in their boiling-houses. 



Of the nature of the colouring matter of cane- 

 juice very little is known ; it becomes darker when 

 the solution is alkaline, and also when submitted to 

 the oxidising action of the air ; hence, when it is 

 desired to obtain sugar of fine colour, it is neces- 

 sary to render the juice slightly acid ; and for this 

 reason only those chemical agents which bleach by 

 reduction are of any value in bleaching sugar solu- 

 tions. 



7 



