Reaction between arsenic III and chromium VI

The reaction between arsenic(III) and chromium(VI) in 0.01-0.05 M sulphuric acid was studied by DeLury . On recomputing his data taking into consideration the dichromate-hydrogen chromate equilibrium 

Edwards has pointed out that, at low acid chromate concentrations, the plot of A /[HCr04][H ] against 1/[H ] is linear but not horizontal. Therefore the rate law 

Mason and Kowalak have found that, in 0.2 M acetate buffer at low concentrations of chromate and high concentrations of arsenous acid, the rate law has the form 

Considering also the stoichiometry of the reaction, we find that 

In the case of high concentrations of chromate and low concentrations of arsenous acid, we must take into account that dichromate ions are also involved in reaction. Thus 

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