Jan., 1921] 
WANN — FIXATION OF FREE NITROGEN 
13 
Table A. Recovery of total nitrogen from ammonium nitrate hy Forster method 
Solution = 1.4285 grams dry NH4NO3 in 250 cc. distilled water 
10 Cc. Solution Made 
Alkaline and Distilled 
Mg. N as NH3 Recovered 
Mg. N as NH3 by 
Calculation 
Mg. Difference 
I 
2 
3 
9.980 
9.896 
9.980 
10.000 
10.000 
10.000 
— 0.020 
— 0.104 
— 0.020 
10 Cc. Solution Digested 
by Foster Method 
Mg. Total Nitrogen 
Recovered 
Mg. Total Nitrogen by 
Calculation 
Mg. Difference 
I 
2 
3 
19.812 
19.540 
19-931 
20.000 
20.000 
20.000 
— 0.198 
— 0.460 
— 0.069 
Table B. Recovery of total nitrogen from ammonium nitrate in the presence of agar agar hy 
Forster method 
Solution of NH4NO3. Total calculated N in 10 cc. = 26.252 mg. 
Total Mg. N Found in 
10 Cc. Solution 
Total Mg. N Found in lo Cc. 
Solution Plus 2 Grams Agar 
Mg. N Found in 2 Grams 
Difco Agar 
Mg. N Recovered 
26.268 
26.219 
26.024 
27.760 
27.372 
26.994 
1.826 
1.741 
1.703 
25-993 
25-615 
25.237 
It is apparent from table B that the agar interferes somewhat with the 
complete recovery of nitrogen. However, as the amount of agar in all 
series was the same in both checks and cultures, the results, though perhaps 
low, are still strictly comparable. 
Results 
The results of the analyses of the cultures are presented in tables 1-9B. 
These are numbered to correspond with the series, each series representing 
a single medium. As already explained, the only constituent of the mineral 
nutrient solution which was varied in the different media was the nitrogen 
source; the latter is indicated in the heading of each table. The presence 
or absence of glucose or mannite is indicated in the sub-heading. In the 
t third column the relative growth in each culture flask is shown by means of 
plus marks; in nearly all cases the growth in the two or three flasks of a 
series inoculated with the same organism was practically the same, but a 
few exceptions may be noted. In the fourth column is given the total 
nitrogen (in milligrams) found in each flask. This figure represents the 
total nitrogen calculated from the titration, minus the average amount of 
nitrogen in the blanks. The other columns are self-explanatory. 
