328 PRODUCTION OF VOLATILE FATTY ACIDS 



The mode of treating the results depended somewhat upon the 

 number of volatile acids found to be present in the cultures under 

 examination. For only two acids the algebraic method^ (page 2036) 

 was used, although the graphical method (page 2040) was found to 

 be som.ewhat more rapid. When three acids were found to be present 

 the graphical method mentioned by Gillespie and Walters (page 

 2054) was followed. This latter method involved much less calcula- 

 tion than the algebraic and was equally accurate. 



As a check on the modified Duclaux method, the formic acid was 

 determined in several cultures by the mercuric chloride method of 

 Franzen and Egger.^ The two methods gave values for this acid 

 harmonizing within 2 per cent of the whole. It is assumed that the 

 values found for the other acids are as accurate. 



In the cultures containing butyric acid its presence was further 

 established by preparing the quinine salt as outlined by Phelps and 

 Palmer^ and determining its melting point. The distillation values 

 accurately establish the identities of the acids, provided the manipula- 

 tions are carefully conducted and the constants are determined with 

 purified acids. 



Sugar determinations were conducted upon the media and several 

 cultures to obtain data regarding the utilization of the sugar and the 

 amount of acid formed therefrom. From 30 to 40 per cent of the 

 sugar was utilized by the bacteria in cultures 2 and 14 days old. It 

 was at first feared that, because the total quantity of volatile acids 

 produced by each organism in the same length of time reached about 

 the same value, not enough glucose was present. It is evident, 

 however, if we view Fig. 1 in the light of this sugar utilization, that 

 the organisms growing in sugar media reached their limiting zones of 

 volatile fatty acid production in the presence of sugar. This may 

 have an important bearing on the growth curve of bacteria. This 

 large yield of formic acid by these bacteria from glucose suggests a 

 possible commercial problem. 



Table I contains a summary of the determinations under the four 

 sets of conditions. Fig. 1 pictures the results of the progressive series 



^ Franzen, H., and Egger, F., /. prakt. Chem., 1911, Ixxxiii, 323. 

 3 Phelps, I. K., and Palmer, H. E., J. Biol. Chem., 1917, xxix. 199. 



