182 Mr Ennos, The Omdation of Ferrous Salts. ' 
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The Oxidation of Ferrous Salts. By F. R. Ennos, B.A, 
St John’s College. (Communicated by Mr C. T. Heycock.) 
[Read 24 February 1913. ] 
THE rate of oxidation of ferrous salts in aqueous solution and 
in absence of free acid was studied by bubbling air or oxygen 
through the solutions at a constant rate of about one litre in 
three hours, portions of the solution being removed at definite 
intervals and titrated with potassium permanganate or bichromate. 
At the ordinary temperature ferrous sulphate and chloride are 
oxidised exceedingly slowly. In the case of the former the initial 
rate of oxidation in an 10 solution at 25° C. 1s of the order ‘03 per 
cent. per hour, and this rate is doubled roughly for a rise of 10°C. 
A temperature of 60° C. was finally employed in comparing different 
ferrous salts and it was found that the oxidation of the chloride is 
about one-tenth and of the acetate ten times as fast as that of the | 
sulphate. For the sulphate the reaction appears to be of the | 
second order as regards the ferrous salt and also proportional to | 
the partial pressure of the oxygen, results agreeing with those | 
obtained by McBain by a different method (Jowr. Phys. Chem. | 
1901). It has not yet been possible to find the order of reaction | 
for the chloride or the acetate. 
The influence of temperature, dilution and nature of the acid 
radicle indicates that the oxidation depends on the non-ionised — 
part of the ferrous salt molecule. It remains to be seen whether | 
there is any quantitative relationship between the two. 
