Sept. lo, 1917 



Formation of ''Black Alkali'' 



583 



chlorid, sodium sulphate, and sodium nitrate may under field conditions 

 exert a protective action upon the organic matter of the soil from the 

 solvent action of "black alkali." 



A 0.5 per cent solution of sodium carbonate was prepared and used to 

 make up soil extracts in the regular proportion of i of soil to 5 of solution. 



Graduated amounts 

 of sodium chlorid and 

 sodium sulphate were 

 added to the solu- 

 tions, which were 

 brought to equilib- 

 rium. The amount of 

 organic matter which 

 went into solution in 

 each instance is indi- 

 cated inTables XLIII 

 and XLIV, and in 

 figure 23. 



A rapid decrease is 

 noticed in the amount 

 of organic matter dis- 

 solved by 0.5 per cent 

 of sodium carbonate 

 when either of the 

 other sodium salts are 

 introduced into the solution. This action is more marked with sodium 

 chlorid than with sodium sulphate. The neutral salts seem to be acting 

 in a protective role upon the organic matter of the soil. 



Table XLIII. — Solubility of organic matter in sodium carbonate in the presence of sodium 



chlorid 



O- J" /o /S ^^ ^S ■JO. 



/^Sy? CS'A^r A^c?C/ a^ A/q^SQi 



Fig. 23. — Graphs showing the protective action of sodimn chlorid and so- 

 dium sulphate upon organic matter of the soil in the presence of so- 

 dium carbonate. 



Table XLIV. — Solubility of organic m,atter in sodium carbonate in the presence of sodium 



sulphate 



