Investigation of Mo(VI) monomer–dimer equilibrium in highly acidic solutions by UV absorbance spectroscopy using refined numerical processing Original Research Article

The chemical forms of molybdenum(VI) in highly acidic media (0.5–3 M HClO4) were investigated by UV absorbance spectrometry at 25°C, confirming the existence of dimeric forms. Comparing the results obtained for various HClO4/NaClO4 mixtures showed that water activity has a greater effect on the dimerization equilibrium than the acidity. A conditional dimerization constant Kd′ can be defined as a function of the perchloric acid concentration. New numerical methods were used to estimate the value of Kd′, which was found to vary according to an empirical law:log(Kd′)=1.55+0.32[HClO4]−0.05[HClO4]2.