Scientific Proceedings. 



79 



54 (197) 



The oxidation of sugars by cupric acetate-acetic acid 

 mixtures. 



By A. P. MATHEWS and HUGH MCGUIGAN. 



[From the Laboratory of Biochemistry and Pharmacology ', Univer- 

 sity of Chic ago. ~\ 



The study was undertaken to learn precisely upon what the 

 oxidizing powers of cupric acetate and Fehling's solution depended. 

 The addition of acetic acid to cupric acetate diminishes its speed of 

 oxidation so that one sugar after another ceases to be oxidized at 

 a rapid rate as more acid is added. The amount of acid that may 

 be necessary to check the oxidation to any given rate depends 

 on the concentration of the acetate ; the more concentrated the 

 acetate the more acid is required. McGuigan determined the 

 amount of acid necessary to check oxidation of the various sugars 

 in different concentrations of the acetate within a certain time (one 

 half minute's boiling). The results showed that the sugars arranged 

 themselves as follows according to the amount of acid necessary 

 to check oxidation. Levulose (most acid required), galactose, 

 glucose, maltose, lactose. 



Solutions of different concentrations of acetate and acetic acid 

 were prepared which would just fail to oxidize levulose to a visible 

 reduction of cuprous oxide on one half minute's boiling. Similar 

 solutions were prepared for the different sugars. Each of these 

 solutions for any given sugar of one per cent, concentration had 

 the same speed of oxidation. 



The cupric ions in these solutions were measured by the elec- 

 tromotive force developed between the solution and a plate of 

 copper. The hydrogen ions were determined by the inversion of 

 cane sugar. From the figures thus obtained the result appeared 

 that in all solutions oxidizing any one sugar with the same speed 

 the decomposition tension of the cupric oxide in the solutions was 

 a constant. 



For the different sugars the following data for decomposition 

 tension were obtained in those solutions that just failed to oxidize 

 to a visible extent in one half minute's boiling. 



