144 



CHEMISTRY OF FARM PRACTICE 



It contains, as a rule, between 12 and 13 per cent of 

 potash (K2O). Sylvinit is similar in appearance to kainit; 

 but it is redder in color. It is someties sold as kainit, 

 and contains a slightly higher percentage of potash, rang- 

 ing from 12| to 15 per cent of potassium oxide (K^O). 

 The disadvantage in the use of these salts is that they 



FIG. 56. Sweet potatoes grown on same soil as those of Fig. 55 but 

 fertilized with phosphoric acid and nitrogen. 



are more expensive per pound of potash delivered on the 

 farm than the purified salts. This is due to the fact that 

 the transportation, charges on a pound of potash in the 

 form of kainit are four times those on the same amount 

 of potash in the form of muriate of potash, because kainit 

 contains 12 to 13 per cent potash, while muriate contains 

 from 48 to 52 per cent. 



The purified potash salts on our market are muriate 



