CONTRIBUTIONS FROM THE CHEMICAL LABORATORY 

 OF HARVARD COLLEGE. 



THE SPEED AND NATURE OF THE REACTION OF 

 BROMINE UPON OXALIC ACID. 



By Theodore William Richards and Wilfred Newsome Stull. 



Received June 16, 1902. 



While the rapid actioD of bromine upon neutral oxalates is well known, 

 there is a difference of published opinion as to whether or not oxalic acid 

 itself is affected by this halogen in aqueous solution. Wurtz * maintains, 

 without stated authority, that action takes place ; while Schonbein f denies 

 this contention, giving brief but inadequate experimental evidence. 



The further study of the behavior of these two substances is therefore 

 an obvious need. Moreover, the outcome must be of practical value no 

 matter which statement should prove to be true : for if bromine really 

 acts upon oxalic acid, the speed of the reaction could not but give in- 

 teresting light as to the disposition of the dissolved acid ; while if no action 

 takes place, a ready mode of separating bromine from chlorine (which 

 reacts readily) might be afforded. 



A few rough experiments sufficed to show that Wurtz was right and 

 Schonbein wrong. The two substances react slowly upon one another 

 at ordinary room temperatures, and rapidly at high temperatures. 

 Schonbein must have been misled by the fact that at 20° no obvious 

 diminution in the intensity of the color of the mixture takes place in 

 many minutes. 



The interest of the problem first centers on the question as to whether 

 the bromine attacks the ion C2O4", the ion HC 2 0/ or the undissociated 

 acid. From the fact that the neutral salt is at once oxidized, the first 

 alternative seemed the most likely ; but the hypothesis of ions is not yet 

 on so stable a basis as to permit certain inference. 



The oxalic acid used in the following work was purified by recrystal- 

 lization from hydrochloric acid and water. It contained no residual 



* A. Wurtz, Diet, de Chem., 2, 671. 



t C. F. Schonbein, J. fur ppt. Chem. 88, 484 (1863). 



VOL. XXXVIII. — 21 



