Sept. 10, 1917 



Formation of "Black Alkali" 



571 



Table XXXV. — Solubility of organic matter and calcium carbonate in 10 per cent solu- 

 tions of sodium chlorid 



Table XXXVI.- 



-Solubility of organic matter and calcium carbonate in 10 per cent solu- 

 tions of sodium sulphate 



As will be seen from Tables XXXIII to XXXVI, with the untreated 

 soil little difference is shown, so far as the action on the organic matter 

 is concerned, between calcium carbonate and other calcium salts when 

 no sodium v/as added. With the h3/drochloric-acid and acetic-acid- 

 treated soils the amount of organic matter fell when the other salts of 

 calcium were present, but rose to practically the same as the untreated 

 soil when calcium carbonate was added. Calcium nitcate, calcium chlo- 

 rid, and calcium sulphate do not alone seem to affect materially the solu- 

 bility of the organic matter of the soil. The acid condition of the soil, 



