373 
Mr Fenton, Oxidation in Presence of Iron. 
(d) Ferric iron although probably inactive in inducing the 
initial oxidation has the effect of encouraging the breaking down 
of the oxidation-product with evolution of carbon dioxide. (Com- 
pare Ruff’s experiments ( loc . cit.) and the formation of mesoxalic 
semi-aldehyde.) 
(e) The oxidizing influence in presence of ferrous iron is 
selective, certain groups only being prone to attack. Nearly all 
the results may be primarily expressed by the replacement of 
hydrogen by ltydroxyl, and this action appears to be chiefly con- 
fined to hydrogen atoms which are directly associated with hydroxyl 
groups. Hydrogen directly associated with a cyclic nucleus how- 
ever, as in benzene and pyromucic acid, and with certain unsatu- 
rated linkages in aliphatic compounds, is also liable to attack. 
The aldehydic HC : 0 group appears to be remarkably resistant 
to the oxidation-process in question. 
(f) In some cases the changes could be most easily explained 
by the supposition that non-hydroxylic hydrogen atoms are simply 
withdrawn, as for example in the oxidation of tartaric acid to 
dioxymaleic acid. This explanation in the latter instance although 
satisfactory in other respects would, according to the hypothesis of 
van ’t Hoff and Wislicenus, necessitate the formation of a fumaroid 
derivative, whereas a maleinoid form actually results. This question 
has recently been investigated by W. F. Cooper of Clare College 
and the author, and their experiments shew that the di-acyl 
derivatives of tartaric acid do not appear to lend themselves to 
the oxidation-process in question, so that the hydroxylic hydrogen 
atoms would appear to be essential. 
Incidental Observations. 
In the process of working out the problems above described 
a large number of interesting observations, not directly connected 
with the primary objects, have been made, and in following up 
some of these side issues results of considerable importance have 
been obtained. It has been considered advisable in the present 
communication to include a very brief account of these in order to 
give an idea of the extent of ground which has been covered. 
Esterification by Ethyl Ether. [Fenton and Gostling, Trans. 
Chem. Soc. 1898. 554.] In studying the properties of dioxymaleic 
acid it was found that hydrogen bromide acted in an interesting 
manner, and various solvents were employed for the reaction. In 
using perfectly pure, dry ethyl ether an unexpected result was ob- 
tained, the product being ethyl dioxymaleate. An excellent yield 
is obtained in this way, and the observation was extended to other 
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