6 BULLETIN 921, U. S. DEPARTMENT OF AGRICULTURE. 



DISCUSSION OF RESULTS. 



These results show that raw cane juice, without the addition 

 of lime, sulphur dioxid, or other chemicals, can be rapidly filtered in 

 an ordinary plate and frame filter press when sufficient infusorial 

 earth of a good grade is added to the heated juice. It is very desir- 

 able, however, that the infusorial earth be of very low specific 

 gravity and also of fine mesh. The best results were obtained with 

 commercial grades of infusorial earth obtained from California, 

 Oregon, and Washington. It is also desirable that the infusorial 

 earth be dry and free from lumps and trash. For successful filtration 

 the infusorial earth must be mixed thoroughly with the juice. If it 

 is wet and lumpy it does not mix well, and if it is trashy there is 

 always trouble with the pump valves becoming clogged. However, 

 with a good, clean, dry grade of infusorial earth, such as is at present 

 on the market, no trouble whatever was experienced in obtaining a 

 steady filtration, a firm press cake with each frame entirely filled, 

 and a filtered liquor bright and clear. 



Most of these experiments were made by adding a weighed quan- 

 tity of infusorial earth to 200 gallons of juice. Based upon a 78 

 per cent extraction obtained by the mill, a dilution of approximately 

 14 per cent, and the average final Brix of the dilute juice, which was 

 13°, this volume of juice is almost exactly the amount obtained from 

 1 ton of cane. With a good quality of infusorial earth 10 pounds to 

 the ton of cane gave a satisfactory filtration. With less than this 

 amount the filtration was slow and there was danger of a slimy, 

 almost impervious, coating forming on the cloths which would retard 

 the rate of filtration. 



With 10 pounds of infusorial earth per ton, 1,200 gallons of juice, 

 or that from 6 tons of cane, could be put through the 18-inch 18- 

 f rame filter press in about three and one-half hours. Using 12 pounds 

 of this earth to 1 ton of cane, a much more rapid filtration resulted, 

 the juice from 5 to 5| tons of cane filtering in two to three hours. 

 With 11 pounds of high-grade infusorial earth per ton, satisfactory 

 results were also obtained, the juice from 5 to 6 tons of cane filtering 

 in about four hours. No trouble at all was experienced in obtaining a 

 steady, clear filtration and a firm press cake. It is not well, however, 

 to try to put through the press a larger quantity of juice than will 

 filter readily under moderate pressure. In the press available for 

 these experiments, using 11 pounds of infusorial earth per ton of 

 cane, it was found best not to try to force through more than the 

 amount of juice from 5-| tons of cane. This amount, filtered in about 

 four hours with a pressure not exceeding 40 to 50 pounds, made a 

 hard and firm cake throughout the entire frame. This press cake 

 could be washed easily and thoroughly and peeled readily from the 



