148 AGRICULTURE 



three hundred feet thick, of a natural deposit 

 of various kinds of potassic and other salts ; 

 which, having been ground up, are put 

 on the market either in their natural con- 

 dition or after undergoing certain methods 

 of artificial concentration. The commonest 

 potash manure is Kainit, a natural salt con- 

 taining about 23 per cent, of sulphate of 

 potassium (including a small amount of 

 chloride of potassium), which is equivalent 

 to 12 J per cent, of pure potash. The materials 

 present in kainit, beside sulphate and chloride 

 of potassium, are sulphate and chloride of 

 magnesium (27 per cent.), chloride of sodium 

 or ordinary salt (36 per cent.), and a small 

 quantity of gypsum. While nothing in 

 kainit is valued except the potash, it is well 

 to bear in mind that fully one-third of the 

 total weight consists of common salt, and 

 for this reason a preference would be given 

 to kainit for the treatment of crops to which 

 it was desired to apply salt. 



The relationship between pure potash and 

 sulphate of potassium, usually called sulphate 

 of potash, is apparent when it is stated that 

 174*2 Ib. of sulphate of potash contain 

 94*2 Ib. of pure potash, combined chemically 

 with 80 Ib. of sulphuric acid. It follows, 

 therefore, that if kainit is guaranteed to 



