Potassic Manures 



Carnallite. 



This is a crude salt of potash extracted at 

 Stassfurt. It is of variable colour, according to the 

 impurities which it contains. It is red, yellow, grey, 

 black, often pink, etc. It is deliquescent, therefore 

 difficult to preserve. Crude carnallite gives bad 

 results when applied to growing crops, being corrosive 

 because of the chlorure of magnesia which it contains. 

 Employed in this form it ought to be buried a long 

 time in advance so as to destroy its harmful cha- 

 racteristics, which are thus eliminated before sowing 

 or planting. If used fresh it is destructive to any 

 crop. It is chiefly used in the manufacture of 

 chlorine and sulphate and potash. It is a compound 

 of chlorure of potash and of magnesia (KClMgCl2 

 6H2O) of water, chlorure of soda, and kieserite. 

 Nearly 2,500,000 tons per annum are extracted and 

 used, for the greater part in the manufacture of 

 chlorure of potash. For this purpose a solution of 

 chlorure of magnesia (MgCl2) is saturated in heat, 

 and the carnallite dissolved in it. The KCl crystal- 

 lises in cooling. 



Sylvinite. 



This is a mixture of common salt and chlorure of 

 potash, etc., extracted at Stassfurt. As it is not 

 largely exported, it is of no particular interest. 



Chlorure or Muriate of Potash. 



When pure, this is a white salt, and takes the 

 form of cubic crystals. It is very soluble in water, 

 and has a salty taste. It is efflorescent, in distinc- 



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