CANE- JUICE CLARIFICATION. 49 



This calcium oxide, commonly known as "quick lime," is the 

 substance desired in clarification. It should be slaked by being 

 placed in water just before it is desired for use. This milk of 

 lime should not be used until after the high temperature caused 

 by the violent chemical action has subsided. On account of the 

 heat involved and the high alkalinity in local portions, it is 

 never safe to apply crude lime to the juice without previously 

 slaking it in water, nor is it advisable to use a quantity of juice 

 to mix this lime, as is quite often practiced in these Islands, 

 since in this case there may be a loss of sucrose, with a resulting 

 dark-colored product, which will impair the color of the clarified 

 juice. The following chemical equation will express the reac- 

 tion when this lime is slaked: CaO (calcium oxide) -f H,O 

 (water) ^Ca(OH) 2 (calcium hydroxide). 



This calcium hydroxide is a substance which is very caustic, 

 and care must be exercised in handling it. Like all bases, it 

 has a great affinity for acid, and consequently its first action 

 is to neutralize part of the acids present. It then coagulates 

 albumins and albuminoids, which form a part of the impurities, 

 and throws down insoluble salts of sulphates, carbonates and 

 phosphates, and of the bases iron and aluminum. These act as 

 mechanical precipitants, assisting in bringing down other im- 

 purities. The compounds of calcium are practically insoluble 

 in cold cane juices, and may be readily filtered, or settled, and 

 the supernatant liquor drawn off. In the addition of lime, as 

 well as in the application of other reagents, much care must be 

 observed that the proper amount is added. If too little is used, 

 there will be poor clarification and settling of the precipitate, 

 while if too much is used, so that alkalinity is reached, and the 

 juice heated to a high temperature, there will be a darkening 

 of the juice caused by the decomposition of the reducing sugars 

 by the calcium, and the formation of dark-colored compounds, 

 which are very hard to remove. If the juice is limed to three- 

 tenths or four-tenths cubic centimeter acidity against N/10 

 NaOH, using phenolphthalum as an indicator, there will be little 

 or no chance of trouble. With the above dangers in view, it is 

 not safe to employ the haphazard methods of liming usually prac- 

 ticed here, but the milk of lime should always be made of stated 

 density and a measured or weighed amount should be supplied 

 to each clarifier of juice, corresponding to prevailing conditions. 



Sulphur dioxide. Where a better grade of sugar than 96 

 test is desired, it is often advisable to subject the juice to fur- 

 ther treatment, one reason for which is to increase the acidity 

 so that a larger amount of lime may be added to effect the clari- 



