Apr. 30, 1917 
Fixation of Ammonia in Soils 
143 
hydroxid solution, was distilled. The distillate was titrated with 
alizarin. 
The acid-extraction method was used in preference to direct dis¬ 
tillation with magnesium oxid, because duplicate determinations by 
acid extraction gave a much closer agreement than could be secured by 
distilling the soil with magnesium. Ten per cent of acid was used, as 
it was found that this amount of acid was necessary to extract as much 
ammonia as would be given off by distilling with magnesium oxid. 
The results stated in the following tables are averages of a number of 
determinations. In no case is a result for a single analysis given, and 
in some instances the figures as given are averages of six or more 
determinations. 
COMPARISON OF METHODS FOR RECOVERY OF AMMONIA FROM SOILS 
Fifty mgm. of nitrogen in the form of ammonium sulphate, chlorid, or 
nitrate were added to 100-gm. portions of soil from Riverside, Cal. 
After standing for 30 minutes, the soils were treated as shown in Tables I 
and II. When the soil was extracted with water only, but little more 
than one-fourth of the nitrogen added was recovered. When extracted 
with increasing strengths of hydrochloric acid, the percentage of nitrogen 
recovered increased with the strength of the acid; but even when the 
acid solution was increased to 10 per cent, only a little more than half of 
the nitrogen added was recovered. 
Table I .—Recovery of ammonia from soil by extracting with water and increasing the 
amount of hydrochloric acid 
Soil extracted with— 
Nitrogen 
added per 
100 gm. 
of soil. 
Nitrogen recovered 
from ammonium 
sulphate. 
Nitrogen recovered 
from ammonium 
chlorid. 
Nitrogen recovered 
from ammonium 
nitrate. 
Mgm. 
Mgm. 
Per cent. 
Mgm. 
Per cent . 
Mgm. 
Per cent. 
Water only... ... 
50. 00 
12. 88 
25. 76 
13. 28 
26. 56 
13. OO 
26. OO 
1 per cent acid. 
50. OO 
22. 12 
44 . 24 
22. 33 
44. 66 
22. 30 
44. 60 
2 % per cent acid. 
50. 00 
22. 68 
45 - 36 
23 - 30 
46. 60 
23. 20 
46. 40 
5 per cent acid. 
50. 00 
24* 36 
48. 72 
24. 74 
49. 48 
24. 50 
49. OO 
10 per cent acid. 
50. OO 
26. 04 
52. 08 
25. 76 
SI- 52 
25.76 
5 1 * 52 
The acid-extraction method and the magnesium-oxid method for 
determining ammonia in soils are compared in Table II. A glance, first, 
at the Riverside soil will show that between 52 and 53 per cent of the 
nitrogen added was recovered by either method. In the Eordsburg soil 
the percentage of nitrogen recovered is much smaller than in the River¬ 
side soil, and it would seem that the magnesium-oxid method was slightly 
more effective than the acid-extraction method, although the difference 
is small. It is observed that the ammonia fixed is practically the same 
whether the ammonia is added as a sulphate, chlorid, or nitrate. It 
would therefore appear that the anions have no effect on the fixation 
of ammonia. 
