16 



THE CARBOHYDRATE ECONOMY OF CACTI. 



An alkaline solution of cupric hydroxide (Fehling's solution) yielded 

 from 100 grams of the following sugars : 



TABLE 2. 



An alkaline solution of silver oxide oxidizes the following sugars with 

 the formation of only three products, carbonic, formic, and oxalic acids. 

 The oxidation is apparently much more drastic than with the other oxidiz- 

 ing agents ; the relative amounts of the three products vary with the nature 

 of the sugar and the concentration and temperature of the mixture : 



TABLE 3. 



D-glucose in alkaline solution when oxidized with air or with 3' per cent 

 hydrogen peroxide yields besides carbonic and formic acids a large amount 

 of non-volatile acids. The latter are a mixture composed of d-arabonic, 

 d-erythronic, 1-threonic, and dl-glyceric acids. The total amounts of these 

 non-volatile acids, as well as the relative amounts of the individual acids, 

 vary greatly, according to whether air or hydrogen peroxide is used as an 

 oxidizing agent. Thus Glattfeld 1 obtained for every 100 grams of glucose 

 oxidized with H 2 O 2 , 23.7 grams of the mixed non-volatile acids, while with 

 air 72 grams of the acid mixture were obtained. 



These illustrations have been cited in order to show the variability of the 

 process of glycolysis even in vitro. Among the important variable factors 

 which influence enormously the course of glycolysis and the nature of the 

 products are the rate of oxidation, concentration, the oxidation potential, 

 temperature, and undoubtedly other less definite elements. It is therefore 

 not in the least surprising that the living organism in which many of these 

 factors are so closely interrelated and almost constantly changing should 



1 GLATTFELD, J. W. E. On the oxidation of d-glucose in alkaline solution by air as 

 well as by hydrogen peroxide. Amer. Chem. Jour., 50, 135-157, 1913. 



