182 SOILS AND FERTILIZERS 



50 per cent, of potassium oxide (K 2 O), and is one of 

 the most concentrated forms of potash fertilizer. It 

 is particularly valuable because it can be safely used 

 on crops as tobocco and potatoes which would be in- 

 jured in quality if muriate of potash were applied, or 

 if much chlorine were present. 



237. Miscellaneous Potash Salts. Carnallit, 9 per 

 cent. K 2 O, composed of KCl,MgCl 2 ,6H 2 O. Poly- 

 halit, 15 per cent. K 2 O, composed of K 3 SO 4 ,MgSO 4 - 

 (CaSO ) 2 ,H 2 O. Krugit, 10 per cent. K 2 O, composed 

 of K 2 SO 4 ,MgSO 4 ,(CaSO 4 ) 4 ,H 2 O. Sylvinit, 16 to 20 

 per cent. K 2 O, composed of KCl,NaCl and impur- 

 ities. Kieserit, 7 per cent. K 2 O, composed of 

 MgSO 4 and carnallit. 



238. Wood Ashes. For ordinary agricultural pur- . 

 poses, wood ashes are an important source of potash. 

 Ashes are exceedingly variable in composition. 

 When leached the soluble salts are extracted and 

 there is left only about i per cent, of potash. In un- 

 leached 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 : 6s 



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 i.i 



Pine 0.8 0.7 



Georgia pine 5 .o 1.2 



Dogwood .* 9.0 5.7 



