28 
BULLETIN 782, U. S. DEPARTMENT OF AGRICULTURE. 
sponds on the plot to a hydrogen-ion concentration of P H 7.65. The av- 
erage hydrogen-ion of the cultures which fermented this acid was P H 
8.1 ; therefore the alkali produced by the fermentation of this organic- 
acid salt can not be due to the formation of sodium bicarbonate alone 
but must be due to sodium carbonate, or a combination of the two. 
In the 14 acids calculated and shown in Table 12 by similar manip- 
ulation of the plot, it was found that 6 of the acid salts, namely, 
citric, malic, succinic, glyceric, tartaric, and malonic produced 
alkali enough to account for the production of sodium carbonate 
alone, or the carbonate and bicarbonate together. The remaining 
acid salts can furnish alkali enough upon complete oxidation to 
account for the entire alkalinity either through the formation of 
sodium bicarbonate alone or a combination of the two. These plots 
do not show exactly the conditions found in the cultures when there 
is a replacement of a strong acid radical by the weak carbonic acid. 
Although these plots show only the effect of the addition of car- 
bonates, they nevertheless clearly indicate the tendency of both the 
carbonate and bicarbonate to decrease the P H value of the medium. 
They further show the relatively weak effect of bicarbonate when 
the medium is at a P H included in the zone where the carbonic- 
bicarbonate equilibrium is obtained, and indicate very nearly the 
quantitative effect of the replacement mentioned above provided the 
acid replaced has a dissociation constant much larger than that of 
carbonic acid. This last condition does in fact apply to all the acids 
studied. 
Table 12. — Theoretical carbonate production from organic-acid salts, together with the 
average Pb value produced by the alkali-forming bacteria. 
Acid. 
Na 2 C0 3 ob- 
tained by 
complete 
oxidation of 
0.01 gram of 
acid. 
NaHCOs ob- 
tained by 
complete 
oxidation of 
0.01 gram of 
acid. 
Equiva- 
lent in 
N/10 alkali. 
Average 
hydrogen- 
ion con- 
centration. 
Gram. 
0. 008275 
. 007905 
. 005887 
. 008974 
. 008822 
.007158 
. 006019 
. 005165 
.004996 
. 007062 
. 01020 
.0152 
. 004341 
. 003838 
Gram. 
0.01311 
. 01252 
. 009333 
.01422 
.01399 
. 01134 
.09541 
. 007997 
. 007921 
.01119 
.01615 
. 01826 
.006882 
. 06084 
C.c. 
1.562 
1.490 
1.110 
1.693 
1.665 
1.351 
1.136 
.9520 
.9429 
1.333 
1.923 
2.169 
.8191 
.7241 
8-53 
8.56 
7.72 
8.32 
8.00 
7.42 
Butyric 
7.27 
7.53 
Glyceric 
8.10 
Tartaric 
8.33 
8.66 
Formic 
8.20 
Benzoic 
7.15 
Salicylic 
7.25 
When hippuric and uric acids and urea were used no other source 
of nitrogen was supplied; therefore the organisms had to obtain both 
their necessary carbon and nitrogen requirements from these com- 
