Sept. lo, 1917 



Formation of "Black Alkali'' 



567 



Portions of acid-treated soil, untreated soil, and soil to which 2 per cent 

 of calcium carbonate had been added were then separately shaken up 

 with the sodium salts in the usual way. When equilibrium was estab- 

 lished, the solutions were filtered off and the soluble organic matter was 

 determined by colorimeter readings against a known standard prepared 

 from peat by extracting the organic matter with ammonia. These 

 results are shown in Tables XXIX, XXX, XXXI, and XXXII and in 

 figures 18, 19, 20, and 21. 



Table XXIX. — Solubility of organic matter in solutions of sodium nitrate 



Table XXX. — Solubility of organic matter in solutions of sodium, chlorid 



Table XXXI. — Solubility of organic inatter in solutions of sodium sulphate 



