[Vol. 10 



220 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



distillate and that if a good condenser was used the receiving 

 flask need not be iced. Likewise, the accuracy of the Messenger 

 titration was tested in this work and the method found to be 



efficient. 

 With this in mind the writer attempted a study of the oxidation 



of citric acid by 



the Messeng 



for the determination of the acetone. As only a short, straight- 

 tube condenser was used the receivers were sometimes iced. 

 Potassium permanganate of the concentration suggested by 

 Pratt ('12) was used for the oxidation. 



In the first experiments, using a known solution of citric acid 

 and the conditions given by Pratt, the yields were extremely 

 low, and although different concentrations of HtPCX were used 

 the yield never rose above 85 per cent. K 2 Cri0 7 and HjSO* 

 were tried under the conditions of the Shaffer method but the 

 yield was low. On trying H 5 SO< with the KMnCh the yield 

 increased to about 90 per cent and was much more constant, nor 

 did any interference occur due to substances formed from the 

 sulphuric acid. In using HsSO, a brown precipitate was formed 

 when the oxidation was complete and KMnO< was still added. 

 Some of the distillations were stopped as soon as the brown color 

 appeared, new receivers were substituted, and the distillation 

 continued. By this method it was found that practically all the 

 acetone yielded by the method had been collected in the first 

 distillate, and no more than traces could be detected in the second 

 receiver. Moreover, tests for citric acid failed when tried on the 

 residue in the distilling flask. 



As the work was being carried out with special regard to its use 

 in culture solutions, the effect of various constituents of culture 



solutions was tried. The non-volatile compounds, such as sul- 



phates and phosphat 



Nitrates gave a 



substance utilizing large quantities of thiosulphate, but this com- 

 pound was readily eliminated in the redistillation from alkali. 

 Various sugars and organic acids were known to form oxidation 

 products, and the yield of aldehyde from malic acid had been 

 studied byJorgensen ('07). These were studied for interference. 

 One-half gram of malic acid was placed in each of 2 Kjeldahl 

 flasks, and 100 cc. of water and 5 cc. of 5 iVII,S0 4 added. The 



