19 
nitrogen bodies not soluble in the solvent. In view of the relatively 
large amounts of amid, basic, and nonbasic nitrogen contained in the 
original humus solutions, it is believed that considerable hydrolysis of 
the proteins occurring in soils has taken place through the action 
of bacteria, and that the humus nitrogen is probably of more immedi- 
ate value as a source of available nitrogen than is the nonhumus 
nitrogen. It seems justifiable to believe, therefore, that the humiilca- 
tion process is really one of importance in soils as a step toward the 
production of available nitrogen compounds. 
DETERMINATION OF HUMUS NITROGEN. 
In view of the large amounts of amid nitrogen obtained in the 
original humus solutions some study was directed to the question of 
methods for the determination of total humus nitrogen. The data 
previously submitted, showing the total humus nitrogen, were ob- 
tained by first evaporating the solutions after acidification with hy- 
drochloric acid, then subjecting the residues to nitrogen determination 
by the use of the regular Kjeldahl method. The determination of 
humus nitrogen is frequently made from ammonia solutions of humus 
after expelling the free and combined ammonia present by distilling 
the magnesium oxid. 1 But on account of the relatively large amounts 
of amid nitrogen found in the sodium hydrate solutions, which, if 
present in corresponding amounts in ammonia solutions of humus, 
would be lost in the magnesium oxid distillation, there is brought 
into comparison the nitrogen of these soils as found in both the sodium 
hydrate and ammonia solutions. The results are recorded in the 
following table: 
Total humus nitrogen by different methods. 
Soil No. 
Amid 
nitrogen 
in NaOH 
solution. 
Per cent 
of soil. 
Total 
humus 
nitrogen 
in NaOH 
solution. 
Per cent 
of soil. 
Total 
humus 
nitrogen 
in am- 
monia 
solution. 
Per cent 
of soil 
Nitrogen 
absorbed 
from am- 
monia 
solutions. 
Per cent 
of soil. 
Soil No. 
Amid 
nitrogen 
in NaOH 
solution. 
Per cent 
of soil. 
Total 
humus 
nitrogen 
in NaOH 
solution. 
Per cent 
of soil. 
Total 
humus 
nitrogen 
in am- 
monia 
solution. 
Per cent 
of soil. 
Nitrogen 
absorbed 
from am- 
monia 
solutions. 
Per cent 
of soil. 
347 
428 
379 
406 
447 
0.100 
.073 
.059 
.039 
.033 
0.774 
.590 
.439 
.226 
.215 
0.657 
.609 
.284 
.179 
.218 
0.502 
.753 
.523 
.264 
.147 
345 
! 343 
1 405 
292 
0.025 
.020 
.026 
.009 
0.147 
.127 
.087 
.058 
0.140 
.117 
.099 
.067 
0.085- 
.175 
.139 
.072 
In some instances much higher percentages of nitrogen were found 
in the sodium hydrate solutions than in the ammonia solutions, and 
in some instances this difference about equals the amid nitrogen con- 
1 In determining the nitrogen in the ammonia Folut ions of humus it was found advantageous to evaporate 
to dryness two portions of the solution. In one the combined ammonia only was determined, which 
amounts were subtracted from the total nitrogen found in the other without distilling with MgO. 
