E, NEWTON HARVEY 



417 



to 



b-J 



I— 

 3 



atmospheric pressure and placed in a thermostat at 20° with safety 

 because the diffusion of dissolved oxygen from the surface into the 

 solution is very slow, if the tubes are undisturbed. 



44 

 40 

 36 

 3Z 

 Z8 

 24 

 ZO 

 16 

 IZ 

 '8 

 4 



u 



T. 



-^ 11 



10 12 14 16 18 20 

 OF OXYGEN 



Z 4 6 

 PER 



Fig. 1. Time necessary for reduction of methylene blue in varying concentra- 

 tions of oxj'^gen. 



It will be noted from Fig. P that the curve is practically a straight 

 line and the time for decolorization proportional to the oxygen con- 

 centration. It is obvious that this method can be used for determin- 



^ The results of this chart were obtained by Mr. J. P. Kelly, Princeton Univer- 

 sity, who undertook the determination at my suggestion. 



