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 2 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 yield of carbon 
dioxide being obtained when water was used as solvent, less with 
amyl 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 
