POTASH FROM FEUDSPATHIC ROCKS 519 



K 2 O, per cent. 



Digestion in distilled water 0.03 



Grinding with water in a mill 0.32 



Digestion in dilute solution of ammonia salts 0.25 



Grinding with same solution 0.57 



Digestion with limewater 0.50 



Grinding wet with calcic sulfate 0.35 



Grinding wet with lime 0.70 



Removal of the alkali by electrolysis 0.50 



Alternative grinding and electrolysis 3.50 



These results indicate that the action of water alone, as well 

 as the combined action of water and other substances found in 

 the soil, carries on the decomposition of fine ground feldspar to 

 a very considerable extent. The high yields of alkali that can be 

 obtained by means of wet grinding and electrolysis indicate that 

 the decomposition might readily go on to complete kaolinization 

 of the feldspar, if any tendency were at work to remove the de- 

 composition products from the surfaces of the particles upon 

 which they are first formed. Since electrolysis does not produce 

 decomposition but merely aids the water reactions by removal 

 of the decomposition products, it would seem probable that in 

 the soil this removal may be done by the plant roots themselves, 

 thus leading to a continual and steady decomposition of the fine 

 feldspathic particles. Until a comparatively recent time the fine 

 grinding of rocks was a costly operation, but the development of 

 improved methods used in the cement industry now makes it pos- 

 sible to grind rocks to extremely fine powders at low cost. 



In 1850 G. Magnus observed that plants could be successfully 

 grown and matured in ground feldspar, which apparently suf- 

 fered decomposition during the process. 11 In 1887 Aitken in 

 Scotland conducted successful plat experiments on a small 

 scale, using Norwegian feldspathic rock rich in potash, ground to 

 I2o-mesh powder. 12 Peas and turnips were the crops used, and in 

 all cases an increased yield was obtained as the result of the use 

 of feldspar. 



11 Journal fur praktische Chemie, 1850, 50 : 65. 



11 Highland and Agricultural Society of Scotland, Transactions, 1887, 

 19 : 253- 



