Mr Fenton, Oxidation in Presence of Iron. 369 



as the concentration of the acid increases. Based upon this 

 observation the authors have devised an extremely simple method 

 by which the relative affinity-values of various acids at 100° may 

 be compared. A given weight of the hydrazone is heated with a 

 known amount of the acid in question, and the resulting carbon 

 dioxide is measured. 



The nature of the above decomposition is explained by 

 assuming the instability of the negative ion 



COOH . CN a HPh . CH 2 C0 2 



and causes which prevent ionization, such as a sufficient concen- 

 tration of hydrogen ions, should have the effect of diminishing 

 the amount of carbon dioxide produced. This hypothesis was 

 tested in various ways with very satisfactory results ; a salt in 

 presence of its own acid, for example, greatly diminished the 

 influence of the latter, and solvents having different ionizing 

 powers gave widely different results, the greatest }deld of carbon 

 dioxide being obtained when water was used as solvent, less with 

 ainyl alcohol, and least with toluene and nitrobenzene. 



Mesoxalic semi-aldehyde. 



CHO 



I 

 CO 



I 



COOH. 



Hitherto all the principal observations upon the results of 

 oxidation in presence of iron have been made with the use of 

 hydrogen dioxide as oxidizing agent. In the earlier experiments 

 on tartaric acid however it was observed that the same effect 

 could be produced, to some extent at any rate, by electrolysis 

 with use of an iron anode and also by chlorine, hypochlorites 

 and other oxidizing agents. 



The effect of oxidizing agents other than hydrogen dioxide 

 is now being investigated by Mr Ryffel and the author, and the 

 first experiment tried has given an important and interesting 

 result. 



Tartaric acid was again first selected for experiment, with 

 chlorine as the oxidizing agent. When chlorine is passed into a 

 solution of tartaric acid at the ordinary temperature the absorp- 

 tion is very slight, although it is shewn that a certain amount of 

 change does occur ; but in presence of ferrous iron (preferably 

 ferrous tartrate) the action is greatly facilitated. Under the 

 latter condition, after saturation with chlorine, the resulting 

 yellow solution soon becomes colourless, and the treatment is then 



