71 



5. This investigation of the distribution of organic nitrogen 

 in the soil indicates a new fraction, the nature of which has not 

 been previously recognized. This is the fraction of nitrogen re- 

 moved from a colorless solution by calcium, iron, and aluminum 

 hydroxides on the addition of calcium hydroxide. The nitrogen 

 retained in this fraction must consist almost entirely of non-pro- 

 tein material, since the organic substances in "this precipitate have 

 been shown to be colorless organic compounds adsorbed by or 

 combined with the metallic hydroxides. This fraction has been 

 reported as nitrogen precipitated by calcium hydroxide. 



6. The true humin nitrogen remains in the residual soil after 

 hydrolysis, but in addition non-humin nitrogenous compounds 

 must also be retained in this fraction. 



7. The strength and volume of the hydrochloric acid used in 

 hydrolysis has little effect On the nitrogen distribution of the hy- 

 drolysate provided acid as strong as constant boiling acid is used, 

 in the proportion of at least two parts of acid to one of soil. 



8. Results gained from a study of different soils -indicate that 

 the organic nitrogen dissolves, during hydrolysis, to almost the 

 same extent regardless of the origin and nature of the soil. 



9. Some very interesting figures are found in the comparison 

 of the different extracts from sphagnum-covered peat (Table 

 XXVI). The portion soluble in sodium hydroxide and not pre- 

 cipitated by hydrochloric acid gives a nitrogen distribution ap- 

 proximating very closely that of a normal plant protein. The nitro- 

 gen dissolving in the preliminary hydrochloric acid leaching shows 

 a nitrogen distribution which is certainly not due exclusively to 

 protein materials, e. g., an ammonia nitrogen percentage of 65.40 

 and amino-nitrogeii-in-filtrate-from-bases of 17.11 per cent. 



10. When an attempt was made to isolate alcohol soluble 

 and salt soluble proteins from the soil the amounts obtained were 

 so small that, it seems safe to conclude that no appreciable quan- 

 tities of these types of proteins are present. 



11. The most significant fact brought out by this study is 

 that the organic nitrogen distribution in different soil types is very 

 uniform. This is to be expected since it has been pointed out that 

 the nitrogen distribution in soils is an average distribution of all 

 the plant and animal nitrogenous products that find their way to 

 the soil. 



