STASSFURT SALTS 191 



236. Miscellaneous Potash Salts. — Carnallit, 9 

 per cent. K 2 0, — composed of KCl.MgCl 2 .6H 2 0. 

 Polyhalit, 15 per cent. K 2 0, — composed of K^SO .Mg 

 S0 4 .(CaS0 4 ) 2 .H 2 0. Krugit, 10 per cent. K a O, — com- 

 posed of K 2 S0 4 .MgS0 4 .(CaS0 4 ) 4 .H 2 0. Sylvinit, 16 

 to 20 per cent. K 2 0, — composed of KCl.NaCl and 

 impurities. Kieserit, 7 per cent. K 2 0, — composed of 

 MgSO and carnallit. 



237. Wood Ashes. — For ordinary- agricultural pur- 

 poses, wood ashes are the most important source of 

 potash. Ashes are exceedingly variable in composi- 

 tion. When leached the soluble salts are extracted 

 and there is left only about 1 per cent, of potash. In 

 unleached ashes the amount of potash ranges from 2 

 to 10 per cent. Soft wood ashes contain much less 

 potash than hard wood ashes. Goessmann gives the 

 following as the average of 97 samples of ashes : 64 



Average composition. Range. 



Per cent. Per cent. 



Potash 5.5 2.5 to 10.2 



Phosphoric acid 1.9 0.3 to 4.0 



Lime 34.3 18.0 to 50.9 



In 10,000 pounds of wood. Potash. Phosphoric acid. 



Lbs. Lbs. 



White oak 10.6 2.5 



Red oak 14.0 6.0 



Ash 15.0 1.1 



Pine 0.8 0.7 



Georgia pine 5.0 1.2 



Dogwood 9.0 5.7 



