2 . The odsorption is not a hinction of the gra11~iIesurface per unit weight. j. The a n i w n t of tlic adsorption is i:ll.:ch greater for sodium hydroxide than for either hydrochloric acid or s o d i u m cliloride. 1.I n the case of itarch-hydrochloric acid, the ordinary atisorption ride is follonwl for Si)ln$
1911
')'he data g i i u in tliis paper, as well as in a Iirevioiis one.' show, in agreement with nunie:'oiis in\-estigations by others, that the ainoiint of amnionia iil soils i,q iiuite irriall: r:inging froiri :I few thoiisands to a few hundreds oi olit' p r ccnt. The 1)rol)ortiun or' nitrite:; and nitrates, too, is in the great imjc!rit>. of c'ax> 1 1 1 + p ~ i i i c ~being i ~ t ~but ;i fe\v thoiisands of one per cent. and 1( , wliich ib true of the soils herein examined. Hence, prricricailj. all of the nitrogen occurring in soils i h o f ari organic nature. This e:iiphatic:all~ypuiiits to t h e iliiportancr. of reyt.drclie> with a Tie\\*to i;.ndiIig out 111~iiaturt' he organic, liitrogenoiis compounds present i\uulcl enable 115. in tlie Grit place, to tetter in the soil. Such ltno\:.l understand the import :I iological In-ocesses of amnionification, nitrification mcl denitril;catim ; t u coniprehentl -!I!.:; t::c r:itrc!gen in one soil is more iiseiiil or a x ailallle than in another: to see wliet!ier there are among the riitrogcvoii.; c(:itill)o.jt:d>~ :.ucii. that are detrimental t o plant life ; and last- h u t not l w ~ t i, t xi11 enable uc to utilize tlie .;oil nitrogel: to better atiwntage than i,s iioxv the case. \T'hile 501i1e iIitr(.)gei1- rin.+ the precipitate from the filter into a beaker and returning to the filter three coiisecuti\ e timei. The ammonia resulting from Kjeldalilizatiori of the precipitate rcpresented the nitrogen of the diamino acids present in the soil. With very few exceptions, all of the estimations given in this paper vrere made in duplicates and their averages only recorded in the tables
CHEMICAL NATURE OF ORGANIC NITROGEN I N SOIL.
12333
Subtracting the sum of ammoniacal, amido, and diamino nitrogen from 100,we find the percentage of monoamino nitrogen. For the sake of convenience the data were arranged in tabular form (see Table V). TABLEV.-AMOUNT
OF
NITROGENIN THE VARIOUSCOMPOUNDS.
Plat.
Gram.
Per c e n t of Per c e n t . of Per c e n t of total soil n i t r o z e n in ovennitrogen soiution. dried soil.
E Total nitrogen in solution (obtained by
J
boiling with hydrochloric acid). . . . Ammoniacal nitrogen. . . . . . . . . . . . . . . . . Nitrogen of acid amides.. . . . . . . . . . . . . Nitrogen of diamino acids. . . . . . . . . . . . . Nitrogen of monoamino acids (difference from 100) ....................... Total nitrogen in solution (obtained by boiling with hydrochloric acid). . . . . . Ammoniacal nitrogbn. . . . . . . . . . . . . . . . . Nitrogen of acid amides. . . . . . . . . . . . . . . Nitrogen of diamino acids. . . . . . . . . . . . . Nitrogen of monoamino acids (difference from IOO).. .......................
0.10380 0.00127 0.02643 0.01306
0.226 0.0027 0.0575 0.0284
81.20
10.21
25.46 12.58
0.06304
0.I371
49.32
60.74
0.=2795
76.23 I .50 20.46 9.91
100.00
0.03435 0.01663
0.1669 0.0033 0.0448 0.0217
0,07445
0.0971
44.36
58.19
0.1161 0.00192 0.03835 0.01432
0.1983 0.0033 0.0655 0.0245
75 -41 1.25
100.00
0.06151
0.093I2 0.00165
0.00252
0.99 20.67
100.00
1.22
1.97 26.85 13.00
Q Total nitrogen in solution (obtained by
boiling with hydrochloric acid). . . . . . Ammoniacal nitrogen. . . . . . . . . . . . . . . . . Nitrogen of acid amides.. ............. Nitrogen of diamino acids. ............ Nitrogen of monoamino acids (difference from 100)......................... U Total nitrogen in solution (obtained by boiling with hydrochloric acid). ..... Ammoniacal nitrogen. . . . . . . . . . . . . . . . . Nitrogen of acid amides.. . . . . . . . . . . . . . Nitrogen of diamino acids. . . . . . . . . . . . . Nitrogen of monoamino acids (difference from 100).........................
9.30
1.65 33.03 12.33
0.1051
39.95
52.98
71.12
100.00
1.26
0.02858
0.1864 0.0033 o.oj72
1.77 30.69
0.01137
0.0228
21.83 8.68
0.0515 2
0.1031
39.35
24.91
12.21
55.33
Having separated the soil nitrogen into the various groups, the next thing to do was to demonstrate that the groups obtained in the manner described actually represented the acid amides, diamino acids and monoamino acids. Acid Amides. Inasmuch as acid amides, by boiling with mineral acids, split off their nitrogen as ammonia, we should naturally expect that the evaporated hydrochloric acid extract of a soil containing amides when distilled with magnesia would give pure ammonia, provided the soil does not contain, in addition to amides, any volatil organic bases. To establish the nature of the distillate the following experiments were carried out: A definit amount of the soil extract, usually from 1000 to 1500 cc.,
I*
