106 MANUFACTURE OF FERTILIZING MATERIALS 



33 9 to 35 Be., it forms soft crystalline needles. 

 It is clear that the size of these crystals must 

 considerably affect the purity of the potassium 

 chloride, as attenuated crystals must retain 

 more mother liquor than large ones, and that 

 consequently they contain more magnesium chlo- 

 ride. It may be remarked in passing that the 

 salt that is deposited on the sides of the crys- 

 tallizers is always more pure than that deposited 

 at the bottom. To obtain high strength prod- 

 ucts, a portion of the two sorts may be taken, 

 especially for continuing the treatment. 



As potassium chloride of 60 to 70 per cent 

 strength is hardly marketable, it is necessary 

 to submit it to new treatment that is, clarifi- 

 cation. For this purpose it is run into vats, 

 termed clarifying vats, fitted with a double 

 bottom covered by cloth or with a network of 

 osiers. It is covered with water, so that the 

 water is 2 to 3 in. above the salt, and left in con- 

 tact with it for five or six hours; then the clari- 

 fied solution No. 3 is run off through a bung- 

 hole in the bottom of the vat. This liquid runs 

 into a special basin, from which it is run into 

 the dissolving pans by a pump. 



If the potassium chloride be not sufficiently 

 enriched by a single clarification, this opera- 

 tion is repeated once or twice until the salt con- 

 tains at least 80 per cent of dry potassium chlo- 

 ride. The above clarifying liquor constitutes 

 a saturated solution. Now a solution of this 



