Reaction between iron II and chromium VI

The fact that the rate of reaction is inversely proportional to the concentration of iron(iri) is explained by Wagner and Preiss on the basis of an equilibrium between chromium(VI) and iron(II), viz. 

In the presence of iodide ions the reaction of iron(II) with chromate induces the formation of iodine. The induced formation of iodine can be represented by reaction (21) and (22). 

Relative rate coefficient, lc3Tjk2i, has been calculated by Wagner end Preiss from the expression 

The induced iodine formation can be formally explained by the following reac- 

However, there is no experimental evidence for an iron(IV) intermediate. 

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