382 | Urea and Ammonia in Placenta 
to cause complete liberation of the ammonia from as much as 
20 cc. of solution when aerated vigorously for 30 minutes. In 
view of the increasing difficulty in obtaining potassium salts as 
well as their increasing cost and the necessity for conservation, 
minimal amounts consistent with adequate action are indicated. 
Table I shows the results of a series of comparative tests when 
using 5 and 10 gm. of solid carbonate, other conditions being equal. 
In view of the fact that large variations in the amounts of NH; 
in the tissue suspensions might cause appreciable variations in 
the efficiency of the amounts of carbonate used, advantage was 
TABLE I. 
Relative Quantity of NH; Liberated from Placenta Tissue Suspensions in 15 
Ce. of Solution When Using 5 and 10 Gm. of K2CO3 and Strong 
Aeration for 30 Minutes. 
NHsz in 100 gm. of placenta tissue. 
5 gm. KeCOs. 10 gm. K2COs. 
me mg. 
22.8 23.0 
16.3 15.8 
13.9 14.4 
12.3 11.9 
11.4 11.6 
fe 7.6 
4.9 4.8 
4.8 4.6 
4.7 4.7 
taken of the NH;-forming ability of urease to produce in some of 
the suspensions higher NH; values. Accordingly, some of the 
figures represent not only the ammonia as such of the tissue, 
but also the ammonia liberated from the urea. 
It is quite plain that 5 gm. of potassium carbonate is a sufficient 
quantity for general use. | 
Time and Vigor in Aeration. 
If two samples of the same tissue differing in weight are aerated 
slowly for 2 minutes and then vigorously at the rate of 5 liters a 
minute for the remainder of 30 minutes, the amount of ammonia 
blown over is proportional to the amount of tissue taken for 
