1923J 



CAMP — CITRIC ACID AS A SOURCE OF CARBON 



269 



This may have been due to the fact that the solution was buffered 

 at a P H favorable for the utilization of the dextrose, and that this 

 buffering stabilized the solution against the effect of waste pro- 

 ducts on the reaction. This is well borne out by a comparison 

 of the data on the P H of the solutions, since on the fourth day 

 solution 1 had reached a reaction of P H 3.8. and solution 2 a rp- 



Fig. 4. Aspergillus sp. in solution 1. 



action of 2.6, and while from the fourth to the tenth day the 

 reaction of solution 1 only reached P H 3.9, solution 2 on the tenth 

 day had a P H of only 3.0, the progress in an alkaline direction 

 having been very gradual. The; difference was not very great 

 but might be sufficient to account for the more rapid utilization 

 of dextrose in solution 2. j 



The utilization of carbon in solution 2 did not indicate a very 

 rapid utilization of citric acid, nor did the titration figures indicate 

 it. Had the experiment been run longer a much larger amount 

 of citric acid would probably have been used. The titration for 

 the blank was 46.6 cc. of N/10 NaOH (for 25 cc. of the diluted 



