CANE SUGAR. 



4. Precipitation with lime and collection of the resulting precipitated 

 phosphates and nitrogenous matter. 



5. Collection of the lees in ponds and subsequent excavation of the * lees 

 mud/ and application as manure. 



The concentration of the lees to a density of 1 '25 would mean an evapora- 

 tion of 90 per cent, of their weight, and even if performed in an efficient 

 multiple evaporator would entail great fuel consumption in value over and 

 above the value of the product obtained. The same obstacle stands in the way 

 of the incineration of the residue, although certain beet sugar factories which 

 work up their molasses for beet spirit treat the 'Schlempe,' or 'vinasse ' (as 

 the lees are termed) for collection of potash residues. 



Lees irrigation has been tried, and there is much to be said in favour of 

 this method of conservation of valuable plant food. Experiments in Scotland 

 have shown that the refuse from whisky distilleries is not, at any rate in the 

 quantities in which it would be applied, injurious to vegetation. Such a 

 scheme was once actually in operation in Demerara, but, the distillery being 

 burnt down and not re-erected, it was not continued. 



Lees when treated with lime give a copious precipitate ; it was found by 

 direct experiment that to completely precipitate 1000 gallons, 1501bs. of 

 commercial lime were necessary. After treatment with lime, lees that con- 

 tained originally *01040lb. nitrogen per gallon now contained -00406 lb., so 

 that over 60 per cent, of the nitrogenous matter was recovered in the precipi- 

 tate. On nitration a sludge was obtained, in volume about 1 5 per cent, of the 

 lees treated; when dry this material contained 3-82 per cent, nitrogen. To 

 treat lees in this way would require no expensive outlay, but the method would 

 still let the potash run to waste ; per 1000 tons of cane, 4 tons more or less of 

 a filtered sludge carrying 50 per cent, water would be obtained, the material 

 containing about 1*9 per cent, of nitrogen. 



The present method of utilizing lees is to run them into a pond or blind 

 trench, which is periodically excavated and the material obtained, a soft black 

 mud, carried to the fields ; this method, while allowing a considerable loss in 

 drainage, is expensive owing to the bulkiness of the material. "Where the 

 estate has a large quantity of cattle, and where the pen manure is systematically 

 collected, the lees can very well be absorbed by the soiled litter. 



In many districts a distillery is not an adjunct of the sugar house, and 

 instead of having lees to dispose of, molasses form the refuse of the factory. In 

 Hawaii the molasses are sometimes returned to the soil in irrigation water, and 

 in Mauritius they often find their way to the manure heaps. Another way of 

 utilizing the molasses is to feed them to the plantation stock, and recover their 

 manurial value in the excreta. 



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