CANE-JUICE CLARIFICATION. 51 



of a very satisfactory grade and color. The method they use 

 requires a great deal of skill and attention in order to yield 

 results that are satisfactory. It is patterned after the process 

 used in beet-sugar factories, with some distinct modifications, 

 which make it applicable to a juice containing glucose, as is 

 always the case with cane juices. 



The object of applying any clarifying material is to effect a 

 rise in purity, and it is especially desirable to remove, in all cases, 

 the substance added, since this itself would tend to act as an 

 impurity and thus give a lower coefficient, if not properly re- 

 moved. The lime, which has been added previously, may be 

 partly removed, as the original precipitate formed, and any free 

 lime or compound which may be easily decomposed will combine 

 with carbon dioxide, forming calcium carbonate or limestone, 

 which is quite insoluble and may be very easily filtered off. 



Ca(OH) 2 (calcium hydroxide) +C0 2 -CaC0 3 (calcium car- 

 bonate) +H 2 (water). 



Whether single or double carbonation is used, the same general 

 methods are employed, and results are expressed by the same 

 chemical equation. 



As stated before, the carbon dioxide may be recovered from 

 the kilns during the burning of lime, as is commonly done in 

 the beet-sugar industry, or it may be purchased in the form of 

 liquid C0 2 contained in heavy iron containers. It is also feasible 

 to use flue gases for this purpose, where a good combustion is 

 obtained, and after they have been properly treated. 



Phosphoric acid. It is sometimes advisable to apply a form 

 of phosphoric acid as a clarifying and precipitating agent after 

 the lime. This may be used in various forms depending upon 

 the individual desires of the operator. 



The compound usually found on the market may consist of 

 one of the following (or a combination of them) : 

 H 3 PO 4 (ortho phosphoric acid). 

 CaH 4 (P0 4 ) 2 (mono-calcium phosphate). 

 Ca 2 H 2 (P0 4 ) 2 dicalcium phosphate). 

 Na,HP0 4 (sodium phosphate). 



The sodium phosphate contains very little acidity, and the 

 main purpose of its use is based on the principle that the sodium 

 is readily given up for any soluble calcium that may be present. 

 This forms the insoluble calcium phosphate, which is easily re- 

 moved as a precipitate or filtered off. The "Reserve Factory" in 

 Louisiana has been using this reagent in their clarification for a 

 long time, where a very good grade of granulated sugar is made. 



Besides these forms of phosphorous, various compounds may 



