TESTING WHEAT FOR PROTEIN 
23 
35 milligrams of nitrogen if a 1-gram sample is digested, or 70 milli- 
grams if a 2-gram sample is digested. These conditions would re- 
quire 12.5 cubic centimeters of 0.2 normal acid when a 1-gram sample 
is digested, and 25 cubic centimeters when 2-gram samples are taken 
for analysis. 
Again referring to the article by Paul and Berry, 14 it is found (1) 
that their figures for the volume of distillation are correct. Accord- 
ing to the figures of this laboratory, namely, practically all the am- 
monia passes over with 75 cubic centimeters of the distillate and all of 
it with 100 cubic centimeters; and (2) when sufficient acid is pres- 
ent to neutralize 85 per cent of the distillate no loss of the uncom- 
bined ammonia takes place. The writers find it is advisable, how- 
ever, to use 50 cubic centimeters of water in the receiving flask so 
that the nose of the glass tubing will be immersed. 
CHOICE OF RECEIVING ACIDS 
So far as receiving acids are concerned, there is apparently no 
difference between hydrochloric and sulphuric. It was thought by 
some that hydrochloric acid would not hold the ammonia distilled 
over at the high temperatures sometimes occurring in the distillation 
flasks. This is not the case, as can be seen by consulting Table 16. 
Table 16. — Influence of temperature on ability of HCL, H 2 SOt, and boric acids 
to hold ammonia 
Acid 
Per cent NH3 retained at a temperature of — 
25° C. 
30° C. 
35° C. 
40° C. 
45° C. 
50° C. 
60° C. 
70° C. 
HCL 
100 
100 
100 
100 
100 
100 
100 
100 
100 
100. 00 
100. 00 
99.25 
100. 00 
100. 00 
98.44 
100. 00 
100. 00 
96.71 
100. 00 
100. 00 
1 90. 19 
100.00 
H2SO4 
100. 00 
Boric 
86.89 
1 Can smell NH3 at this temperature. 
This table records the data comparing the ability of HCL, H 2 S0 4 , 
and boric acid to hold ammonia at increased temperatures. For this 
study, 10 cubic centimeters of approximately 0.1 normal NH 4 OH 
was added to 0.1 normal HCL and H 2 S0 4 , and 4 per cent boric acid 
solutions. The acid was present to the extent of 50 per cent more 
than was necessary to neutralize the ammonia. The temperature 
varied in 5° intervals from 25° to 50° C, then by 10° intervals to 
70°. It will be seen that there was no loss of ammonia when hydro- 
chloric or sulphuric acid was used, but that boric acid began to lose 
ammonia at 40° and the quantity lost gradually increased as the tem- 
perature was raised to 70°. 
Boric acid will also release or lose ammonia on standing. Titra- 
tions were made after adding ammonia and allowing to stand for 
1, 2, 3, 4, 5, 6, 7, 8, 16, and 24 hours. No ammonia was lost in 4 hours 
but at the end of 5 hours, 0.85 per cent of the original ammonia was 
lost and at 6, 7, 8, 16, and 24 hours, 0.86, 1.23, 1.99, 2.89, and 5.18 per 
cent of ammonia was lost at the intervals listed. Boric acid, there- 
14 See footnote 8, 
