1913] GODDARD—SOIL FUNGI 281 
of ammonia, as in nitrogen-free cultures, the distillate was passed 
into N/2o sulphuric acid, which was then titrated by the use of 
N/2o sodium hydroxide. In some cases with larger nitrogen 
content, N/ro or even N/s5 solution of the acid was used. 
Ammonia-free water was employed for all the distillations. The 
distilled water of the laboratory was found to contain o. 21 mg. of 
nitrogen in 300 cc. of the water. The ammonia-free water for this 
was prepared by the evaporation of distilled water to one-halfits origi- 
nal volume after the addition of a small piece of sodium hydroxide. 
After the titration, the quantity of nitrogen was calculated as 
follows: 1 cc. N/ro sulphuric acid is equivalent to 1 cc. N/10 
ammonia (NH;); 1cc. N/ro ammonia contains 1.404 mg. of 
nitrogen; then the nitrogen present is equal to the number of cc. 
of N/tio acid used times 1.404 mg. 
All chemicals used in the analyses were the purest that could be 
obtained. The sulphuric acid was marked “Baker and Adamson, 
standard purity.” At the same time, the purity of the chemicals 
was tested by a blank in which only the chemicals were used. 
This showed the chemicals used in the nitrate-free method to con- 
tain 0.42 mg. of nitrogen, and in the nitrate method 0.56 mg. 
The amount of the proper blank was subtracted in each case from 
the total nitrogen of the determination. The filters used in separat- 
ing the mycelium from each of the cultures were analyzed and found 
to be nitrogen-free. 
The apparatus employed for the digestion consisted of 500 cc. 
Kjeldahl flasks of the oval form, each provided with a straight 
bulb tube, which was inserted in the neck of the flask to prevent 
loss of sulphuric acid. The distillation was carried out in 500 cc. 
round bottom Jena flasks. These were connected with Kjeldahl 
bulbs by means of rubber stoppers, and the bulbs led into glass 
condensers which were placed in an upright position. The distil- 
late was collected in a 500 cc. Erlenmeyer flask. The burettes 
used for the titrations were the most carefully standardized, with 
enamel backs and a blue line for accurate readings. All apparatus 
and utensils were washed with the greatest care after use each time. 
In addition, they were rinsed at least twice with distilled water, 
after which they were either inverted or covered. 
