Superphosphates Potash 97 



and most generally used. It varies somewhat in composi- 

 tion, according to the method of manufacture, though 

 practically only three grades are met with in this country 

 and only one of these is used to any great extent for agri- 

 cultural purposes. These grades are : 



Basis 98 per cent pure . . contains 61.9 per cent actual potash 

 Basis 95 per cent pure . . contains 60.0 per cent actual potash 

 Basis 80 per cent pure . . contains 50.5 per cent actual potash 



The last grade is most common, and because it absorbs 

 moisture is guaranteed to contain 48 per cent actual 

 potash, though the absorption of water makes little differ- 

 ence because it occurs after the material is placed in the 

 bag and hence the correct amount is contained even if it 

 is slightly diluted. The chief impurities of muriate of 

 potash (chlorid) are common salt, or sodium chlorid, and 

 insoluble matter, which are not deleterious substances. 

 The lower the content of potash, the higher the content of 

 impurities, though in all cases this form of potash is sold 

 upon the basis of 80 per cent muriate. 



High-grade sulfate of potash. 



High-grade sulfate of potash is manufactured and used 

 in much smaller quantities than muriate. It is made 

 from muriate and kieserit at the present time, though 

 formerly was manufactured exclusively from kainit. The 

 commercial product contains from 47 to 52.7 per cent of 

 actual potash, or about 90 to 96 per cent of pure sulfate of 

 potash, though the most common grade contains 48 per 

 cent of actual potash. It naturally varies somewhat in its 

 composition, owing to impurities, either introduced or 

 imperfectly removed. It is, however, regarded as prefer- 

 able to the muriate for some crops, for reasons already 



