THE COMPOSITION OF THE SOIL 147 



Morrow^ has shown that the figures for the distribution of 

 nitrogen given by the van Slyke method are unreliable in 

 presence of ferric chloride, which always occurs in soil ex- 

 tracts. Potter and Snyder have studied the amino-nitrogen 

 in soil.'' 



^ Soil Sci., 1918, 5, 163. 



^yourn. Amer. Chem. Soc, 1915, 37, 2219, and Journ. Ag. Res., 1916, 6, 61. 



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