Java factories have been the foremost in elaborating a system, through their eminent technologists, so that today one may find the bulk of the sugars they turn out from certain factories 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 removed. 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) + CO2—>CaCO3 (calcium carbonate) + H2O (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 CO2 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):
- H3PO4 (ortho phosphoric acid).
- CaH4(PO4)2 (mono-calcium phosphate).
- Ca2H2(PO4)2 (dicalcium phosphate).
- Na2HPO4 (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 removed 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 be found on the market, under trade names, which have as their base the above acid. “Clariphos” is one of these compounds, which has found extensive use in many of the Louisiana sugar factories.