MANUAL FOR SUGAR GROWERS. 113 



diice the density to about 20° B., and lime added, 

 plienol-phthalein being used as an indicator ; the 

 mixture is heated in a steam-heated vessel or "blow- 

 up," carefully skimmed, to remove impuiities, and 

 boiled to grain in the vacuum pan, yielding second 

 crystals. It is often the practice to submit the 

 syruj) obtained by this operation to similar treat- 

 ment, thus obtaining a small quantity of third sugar. 



It is possible to obtain upwards of ninety-two to 

 ninety -three per cent, of the total cane sugar in the 

 juice in the form of crystallised sugar, and upwards 

 of seventy-four per cent, should be in the form of 

 first crystals. With good working the quantity of 

 molasses should not exceed fifteen to twenty gallons 

 per ton of sugar made. 



Various processes are employed to produce sugar 

 of fine colour direct from cane-juice. The one most 

 commonly employed consists in decolourising the 

 syrup by means of sulphurous acid. When sulphur 

 is burned, pungent fumes of sulphur dioxide are 

 given off, which dissolve in water, forming sulphur- 

 ous acid. This substance has powerful bleaching 

 action on most vegetable colouring matters and in 

 the act of bleaching is itself converted into sul- 

 phuric acid. To apply this in the sugar industry 

 sulphur is burned in a small furnace, and the fumes, 

 urged forward by means of a steam jet, are brought 

 into contact with the cane-juice, by which they are 

 dissolved and Avhich they decolourise. There is 

 some difference of opinion as to the best time in 

 the treatment of the juice at which to apply the sul- 

 phurous acid. Some apply it as the juice runs 

 8 



