ip/o] CARBON, PHOSPHORUS AND NITROGEN IN SOILS 95 



by treatment with a mineral acid; yet, if this artificial liumic acid 

 be heated in a current of ammonia gas, combination took place and 

 the resulting compound could not be decomposed by treatment 

 with mineral acids. He, therefore, concluded that the nitrogen 

 formed an integral part of the humic acid radical. 



Berthelot and Andre (26) studied artificial humic acid pre- 

 pared out of sugar. This acid formed salts with various bases, 

 which were easily decomposed again by treatment with an acid, 

 except in the case of the ammonium sali, the nitrogen of which 

 could not be entirely liberated by this treatment. They concluded 

 that the nitrogen in part at least, formed an integral part of the 

 humic acid radical. 



Hilgard arid Jaffa (3o),4n 1892, propounded their well known 

 view regarding the importance of the nitrogen associated with the 

 extracted matiere noire. 



Berthelot and Andre (31) regarded the organic matter of the 

 soil as of great importance since it prevented the loss of nitrogen 

 thru drainage since the nitrogen was held in insoluble combination 

 in the organic matter. 



Fulmer (38) determined the humic nitrogen in 53 samples of 

 Washington soil and attempted to work out the relationship be- 

 tween carbon and nitrogen by means of the formula c= ^~, 

 where c= the percentage of nitrogen in the matiere noire; b= 

 the percentage of the total soil nitrogen; a= the percentage of 

 humus. By means of this formula the 53 samples of soil were 

 separated into three classes; the first class contained 19 samples in 

 which the variation in the humic nitrogen calculated by means of 

 the formula was within one percent of the analytical result; the 

 second class contained 10 samples and the variation was from one 

 to two percent ; the third class contained 24 samples and the varia- 

 tion was anywhere over two percent. These results furnished good 

 evidence that no one given relation would hold for all soils. 



Wheeler (48) found that lime or gypsum caused a decrease in 

 the amount of humus but that the percentage of humic nitrogen 

 was increased. Similar results were obtained by Frear and Hess 

 (54) on manured land. 



Dojarenko (56) recently studied the "humic" nitrogen of soils. 

 He determined the total, humic, amid, ammoniacal and amido ni- 

 trogen in seven samples of black Russian soils. The results are 

 reported in Table 2. 



