MANUAL FOB SUGAR GROWERS. 115 



stance, falls to the bottom of the vessel, carrying 

 with it a considerable amount of impurities and col- 

 ouring matter. The carbonic acid required for this 

 process is usually obtained from the kiln in which 

 the lime for the use of the factory is burned. 



In the phosphoric - acid process, lime is added to 

 the juice in somewhat larger quantities than is re- 

 quired to effect clarification in the ordinary way. Af- 

 ter the removal of the scum, phosphoric acid is 

 added to the juice, when an insoluble phosphate of 

 lime is produced, which is best removed by sub- 

 siding ; this precipitate carries down with it colour- 

 ing matter and other impurities. Various forms of 

 phosjDhoric acid are on the market, so prepared as to 

 render them easy of carriage. The process is one 

 requhing no special appliances, and is easily carried 

 out. 



The use of animal charcoal is but rarely resorted 

 to in the colonies. For the removal of the colouring 

 matter from the juice no other agent so completely 

 decolourises sugar solutions. The difficulties attend- 

 ing its use are such as can only be successfully coped 

 with when the manufacture is conducted on a very 

 large scale. Its use is almost entirely confined to the 

 process of refining. The charcoal is placed in ii^on 

 cylinders 5 or 6 feet wide and 20 or more feet high. 

 The juice after clarification is allowed to flow in at 

 the top of the column, and after percolating slowly 

 through the charcoal it flows out at the bottom in a 

 colourless state. After having been in use for some 

 time the charcoal loses its decolourising properties ; 



