3o6 



CHAPTER XVII 



and, when the rate of filtration slows down, completes the filling at a pressure 

 of 40 lbs. per sq. in. The washing is effected by a third centrifugal pump at 

 a pressure of 60 lbs. per sq. in. 



In filtering decanted juices and second carbonation juices and syrups 

 through either a leaf filter or a chamber press, it is not usual to employ a 

 pump. Better results are obtained when the filtration takes place under a 

 head of about ten feet. 



In order to preserve the expensive heavy cloth, beet sugar practice 

 places over this a very thin inexpensive cloth, which may be frequently 

 renewed at a net saving in expenditure. 



Fig. 182 



Capacity of Filters. — There is so much variation in the rate at which 

 cane products filter, and so much variation in the demands made by different 

 houses on this station that it is impossible to give anything more than a 

 very rough statement, which is referred to a weight of juice equal to that 

 of the cane. 



Defecation. — With juice equal to cane, scums 10 per cent, on the volume 

 of the juice and dry matter in the scums 0-3 to 0-4 per cent, on cane, a 

 filtering area of 65 sq. ft. per ton-cane-hour will be sufficient, provided no 

 washing is required. This figure is to be considered a minimum, and 80 

 sq. ft. per ton-cane-hour would be a better allowance. When washing of the 

 cake is required, from 100 to 120 sq. ft. per ton-cane-hour should be allowed. 

 The same figure will serve when double pressing is followed, since the second 

 pressing is much more rapid than the first. When the whole volume of the 



