24 



concentrated acid and the residue analyzed. His results calculated 

 on the ash free basis showed the residue to contain 64.11 per cent 

 carbon, 3.35 per cent hydrogen, and 0.80 per cent nitrogen. The 

 residue becomes lower in nitrogen*, hydrogen, and ash but richer 

 in carbon as the hydrolysis is continued. 



Detmer (1871) pointed out that similar results were true in 

 peat beds where the deposits remained undisturbed for years. He 

 found that there is an increasing carbon and nitrogen content of 

 the humus for varying depths. This is shown by the following 

 table : 



Likewise Gortner (1917) observed 



that there is a much greater wastage of carbon than nitrogen. Hilgard 

 (1906) calls attention to the increased nitrogen content of the humus over 

 that of the original vegetable materials. If we take the average carbon con- 

 tent of proteins as 51.15 per cent (average of 30 analyses given by Mathews 

 1915) a C:N ratio of 3.06 found in soil A-1916 would give a nitrogen content 

 of 16.71 per cent, which approaches very nearly to the average nitrogen content 

 of these 30 proteins, i. e., 17.66 per cent. It is evident that the materials re- 

 maining in the soils are rapidly increasing in nitrogen content. 



Suzuki (1906-08 c) made further studies on a 500 gram sample 

 of the humic acid obtained from Merck. It was hydrolyzed with 

 concentrated acid and the solution obtained subjected to esterifica- 

 tion and fractional distillation according to the method of Fischer 

 (1901). He obtained: 



Alanine 2.39 gm. 



Leucine , 2.16 gm. 



Alanine + aminovalerianic acid 0.11 gm. 



Aminovalerianic acid 0.57 gm. 



Proline (copper salt of active proline) . 0.67 gm. 



(copper salt of inactive proline) (?) 0.50 gm. 



Aspartic acid 0.06 gm. 



Impure aspartic acid (?) 3.16 gm. 



Glutaminic acid present 



Tyrosine trace 



Histidine trace 



Ammonia 1.90 gm. 



Copper salts of unknown acids 30.30 gm. 



As these compounds are typical protein decomposition prod- 

 ucts, his work proves that the humic acid examined by him was 

 either of a protein nature, a mixture of protein decomposition prod- 

 ucts, or probably both together with some as yet unknown com- 

 pounds. Unfortunately, the origin of the acid was unknown to 

 Suzuki, but he states that it was probably prepared from peat. 



From a study on Michigan peat soils Jodidi (1909) has con- 

 cluded that the bulk of the organic nitrogen is made up of acid 

 amides, di-amino acids, and mon-amino acids. He used slightly 

 modified methods. The ammonia was determined as above by 

 distillation with magnesium oxide. The residue from distillation 

 with magnesia was dissolved in dilute sulfuric acid and the 



*He stated that although the nitrogen content decreases, it is very difficult 

 to entirely remove all of the nitrogen. 



