112 MANUFACTURE OF FERTILIZING MATERIALS 



and steam and consequently . fuel. This draw- 

 back is obviated by diluting the solution which 

 flows from the clarification vats, with water, 

 so that after complete cooling it yields chloride 

 of potassium of high strength directly, and 

 no longer carnallite. In this way the crystalli- 

 zation and solution of carnallite is conducted 

 in a single operation. The advantages of this 

 method of working are evident: Instead of treat- 

 ing as before, two different solutions and two 

 different salts, only a single solution and a single 

 salt have now to be treated. /The potassium 

 chloride so produced is so pure that when it 

 is freed from magnesium chloride by a little 

 water, it contains only 0.5 per cent of common 

 salt, all the rest being potassium chloride with a 

 little moisture and some slight impurities. 



In the manufacture of potassium sulphate, 

 the process is by drenching potassium chloride 

 with sulphuric acid and calcining in a rever- 

 beratory furnace. The reaction which takes 

 place is the same as that used to manufacture 

 sodium sulphate from common salt and sul- 

 phuric acid. First of all the material heats, 

 gaseous hydrochloric acid is given off, and acid 

 potassium sulphate formed. Afterwards the 

 temperature continuing to rise, the acid sulphate 

 of potassium being weak acts on the remainder of 

 the potassium chloride. A new disengagement 

 of hydrochloric acid gas is produced, and finally 

 potassium sulphate remains as a solid mass. As 



