COMMERCIAL FERTILIZER MATERIALS 463 



potash, especially in the United States. Kelp, saline brines, 

 deposits in old lake beds, and flue dust yielded considerable 

 potassium. Most of these sources, however, are too expensive 

 to compete with European potash in normal times. 



260. Stassfurt salts and their refined equivalents. — The 

 Stassfurt salts contain their potassium either as a chloride 

 or as a sulfate. The chloride has the advantage of being more 

 diffusible in the soil, but in most respects the sulfate is pref- 

 erable. Potassium chloride in large applications has an in- 

 jurious effect on certain crops, among which are tobacco, 

 sugar-beets, and potatoes. On cereals, legumes, and grasses 

 the muriate appears to have no injurious effect. 



Kainit is the most common of the crude products of the 

 Stassfurt mines and is imported into this country in large 

 amounts. It is generally a greyish vari-colored salt, soluble 

 in water and alkaline to litmus. It carries from 12 to 14 

 per cent, of KgO, largely as potassium sulfate. Its potash 

 is immediately available to the crop. Below is a typical 

 analysis : 



K,SO, 21.3 



KCl 



MgSO^, 



MgCla 



21.3 



NaCl 



34.6 



2.0 



CaSO^ 



1.7 



14.5 



Insoluble 



8 



12.4 



H„0 



12.7 



Silvinit contains its potassium both as a chloride and as a 

 sulfate. It also contains sodium and magnesium chlorides. 

 Potash constitutes about 16 per cent, of the material. Owing 

 to the presence of chlorides, it has the same effect on plants 

 as has kainit. There are a number of other Stassfurt salts, 

 consisting of mixtures of potassium, sodium, and magnesium 

 in the form of chlorides and sulfates. They are not so widely 

 used for fertilizers as are those mentioned above. 



A great proportion of the crude salts are refined for ex- 

 port purposes, appearing on the market as either the chloride 

 or the sulfate. They usually contain from 48 to 50 per cent. 



