LABORATORY FOR PLANT PHYSIOLOGY. 55 



Oxidation of Glucose by Means of Air, by H. A. Spoehr. 



The marked stability of hexoses in pure solution toward oxidizing agents 

 as compared to the apparent ease with which these sugars are oxidized in 

 the living organism has led to extensive speculation as to the chemical nature 

 of glycolysis. While it has been known for some time that oxidation of the 

 sugar can be effected by raising the reduction potential of the sugar solutions 

 through the addition of alkali, there is considerable doubt whether the degree 

 of alkalinity necessary to bring this about exists in the living organism. 

 On the other hand, when the hydroxyl-ion concentration is lower (0.3 molar 

 NA2HPO4) air is incapable of oxidizing the sugar. For a continuous oxida- 

 tion of glucose with air it is clear that certain conditions must be met, viz: 

 (1) activation or dissociation of the glucose molecule; (2) activation of at- 

 mospheric oxygen through catalysts or oxygen carriers; (3) proper buffer 

 solutions to prevent the accumulation of the acid products of sugar oxidation. 

 After considerable experimentation, these conditions have been most ade- 

 quately met by the following system : The sugar is dissolved in a solution of 

 Na2HP04 and NaH2P04. This mixture, it was found, decolorizes a solution 

 of methylene blue, and, on passing air through the solution, the blue color 

 is again formed and CO2 is liberated. However, the rate of sugar oxidation 

 of this mixture is low. A number of substances accelerate the reaction; thus 

 far the most effective agent in this respect has been found to be iron. A 

 large variety of iron compounds have been tried, including a number of 

 complex colloidal preparations. In all of these, however, the iron precipi- 

 tates out in time, usually as the insoluble ferric phosphate. This was finally 

 overcome by using the complex salt formed by dissolving FeS04 in sodium 

 pyrophosphate. 



The chemical reactions resulting in the complete oxidation of glucose in 

 this manner are undoubtedly very complex, involving a number of steps. In 

 all probability the following reactions express the more important steps, all 

 of which are catalyzed by iron: 



C6Hi206+methylene blue — >6C02+6H20+leuco methylene blue 

 02+leuco methylene blue — > methylene blue+H202 

 C6H12O6+H2O2— >6C02+6H20 



Thus, by drawing air through a glucose solution containing the sodium- 

 phosphate mixture, the iron-pyrophosphate complex and methylene blue 

 in 0.001 molar concentration, considerable quantities of the sugar are oxi- 

 dized with the formation of CO2. The investigation is being continued with 

 a view of determining whether the role of the phosphate mixture is that of an 

 isomerizing agent, converting the glucose into levulose, as the latter sugar is 

 much more easily oxidized than glucose, or whether the function of the phos- 

 phate is one of salt formation. The rate of reaction can be further increased 

 by the use of certain promoters and adsorbents — this, however, further 

 complicates the system. It is evident that the kinetics of the reaction in the 

 dark and in a homogenous system must first be established before a rational 

 interpretation of the effect of light thereon can be attempted. 



Isolation of Phosphatides from Opuntia discata, by Earl B. Working. 



The attempt was made in this work to obtain phosphatides from active 

 growing cells rather than resting or storage tissue. The season was unsatis- 

 factory from this viewpoint, as the excessive drought inhibited the growth of 



