20 
tained in the sodium hydrate solutions. Rimbach l has shown that 
the humus nitrogen as determined in sodium hydrate and ammonia 
solutions, respectively, occurs in greater amounts in the former solu- 
tions, from which he concluded that sodium hydrate dissolves more 
nitrogen than ammonia. Similar observations have also been made 
by others. From work done in this laboratory it is doubtful whether 
sodium hydrate actually dissolves more nitrogen than ammonia, but 
rather that the increased amounts found represent amid nitrogen, 
which is lost in the methods employed in the determination of total 
humus nitrogen from ammonia solutions. 
While the amounts of ammonia absorbed by the residues left after 
evaporating to dryness ammonia solutions of humus bear no definite 
relation to the amounts of humus nitrogen present, the absorption of 
ammonia by humus took place to a considerable extent, and correc- 
tion should be made for this in humus determinations, as has been 
pointed out by Emery - and others. 
PERCENTAGE OF NITROGEN IN HTJMTJS OF HAWAIIAN SOILS. 
Hilgard 3 has shown that humus from arid regions contains a higher 
percentage of nitrogen than humus from humid sections. He found 
that humus from arid regions contained on the average 15.23 per 
cent nitrogen, while the humus from humid regions contained only 
4.23 per cent. In the work on soils at this station many humus and 
humus nitrogen determinations have been made and some of the 
results obtained are submitted in the following table: 
Total humus arid humus nitrogen in Hawaiian soils. 
Soil "To. 
Humus. 
Fer rent 
of soil. 
347 14.81 
423 14.31 
379 8.20 
406 3.0> 
447 3.61 
345 1.74 
343 2.45 
405 1.74 
292 1.80 
282 2.77 
283 1.78 
284 2.72 
Humus 
Humus 
ash. Per 
nitrogen. 
cent of 
Per cent 
soil. 
of humus. 
2.28 
5.16 
3.89 
4.12 
1.91 
5.35 
1.64 
7.33 
1.54 
5.94 
1.13 
6.88 
1.73 
5.21 
1.07 
4.91 j 
1.87 
3.21 
1.04 
7.87 
.79 
6.40 
.70 
5.62 
285. 
2v6. 
287. 
2S8. 
312. 
313. 
314. 
315. 
316. 
317. 
Soil No. 
Average. 
Humus. 
Per cent 
of soil. 
2.03 
3.15 
3.64 
3.06 
5.26 
4.14 
3.94 
4.33 
3.39 
5.12 
Humus 
ash. Per 
cent of 
soil. 
Humus 
nitrogen. 
Per cent 
of humus. 
0.63 
.94 
1.38 
1.48 
1.19 
1.44 
1.17 
.79 
.81 
1.18 
9.85 
10.35 
7.31 
5.88 
5.27 
6. 85 
6.81 
6.36 
6.22 
6.32 
5.88 
These data show that the humus of Hawaiian soils contains nitrogen 
in amounts similar to those of humid soils elsewhere. Some of the 
soils used in this investigation (Xos. 379 and 447) came from sections 
which have been designated as arid, but the arid conditions which 
now prevail in these sections have probably not existed as such for 
: Loo. eft. 
2 Jour. Amer. Chem. Soc., 22 (1900), p. 285. 
3 Soils. New York and London, 1907, pp. 136, 137. 
