INTRODUCTORY DISCUSSION. 



15 



recently has also been studied in relation to the absorption of water and 

 growth. 



From a study of the action of alkalies on the pentoses in the absence of 

 oxygen or an oxidizing agent, some insight can be gained into the formation 

 of malic acid in the succulents. When a solution of 1-arabinose is thus 

 treated with eight times normal sodium hydroxide there is formed a variety 

 of acid products. Special interest is attached for present consideration to the 

 dl-1, 3-dioxybutyric acid: dl-2, 3-dioxybutyric acid: 



OH H H OH 



COOH- 



-CH 3 OH, 



COOH- 





-CH,OH 



By oxidation these acids go over easily into d-1 malic acid. 1 



Finally, to turn to the action of alkalies or metallic salts on sugars in the 

 presence of oxygen or oxidizing agents : The relative stability of the sugars 

 in aqueous solution toward oxidizing agents and the influence of small 

 quantities of metallic salts has already been mentioned. Before entering 

 upon the discussion of the way in which alkalies and salts affect the sugar 

 molecule, it will be helpful to indicate the products which are formed in the 

 oxidation of sugars. The nature of the products and the relative propor- 

 tion of these varies tremendously with different conditions and depends 

 upon a number of factors, more especially the concentration of the alkali or 

 salt, the oxidation potential, i. e., whether the oxidizing agent is air, hydro- 

 gen peroxide, cupric hydroxide, silver oxide, etc., and the temperature. The 

 different sugars also show wide variation in the proportion of the products 

 formed. Thus, for example, certain sugars yielded as shown in table 1 : * 



TABLE 1. 



1 NEF, J. U. Liebig's Annalen, 376, 13-52, 1910. 

 1 SPOEHB, H. A. L. c., p. 234. 

 8 NEF, J. U. Liebig's Annalen, 403, 244, 1913; Ibid., 357, 220, 1907; Ibid., 357, 

 1907. 



