CANE SUGAR. 



Sand Filtration. In Fig. 156 is shown the general type of appar- 

 atus used for sand nitration ; it consists of a cylinder a a about 6 ft. high, 

 and 2 ft. in diameter ; within the cylinder is arranged a perforated pipe I b 

 about 8 in. in diameter ; between the pipe and the outer casing are a number 

 of conical rings, each about 3 in. high, and standing one on top of the other ; 

 the space between the central pipe and these rings is filled with sand ; the 

 juice or other material to be filtered enters by the pipe c c, fills the cylinder, 

 passes through the sand into the perforated pipe and is discharged through 

 the pipe dd\ the sand when foul is discharged through a manhole at the 

 bottom of the cylinder and is easily washed in a stream of water. The 



FIG. 156. 



perforations in the pipe are of such a size that the sand does not pass through. 

 The capacity of these filters varies with the nature of the juice and with the 

 size of the grains of sand used ; as a general rule two filters of the size quoted 

 above should be sufficient for every 1000 gallons of juice per hour.. 



The advantages of mechanical or of sand filtration are most pronounced 

 when high class direct consumption sugars are being made, and to this end they 

 form an invaluable adjunct to the factory ; it has also been found that they 

 remove large quantities of suspended matter, and have a very useful effect in 

 lessening the deposit of scale in the evaporators, and thus materially adding 

 to their capacity. 



280 



