Oxoacids of molybdenum VI

This process seems to take place because of the extremely strong acidic properties of Mo03. The cation particle Mo02+ adds chloride ions forming the oxochloride Mo02C12 which is volatile under the experimental conditions, and evaporates from the chloride melt as white smoke 

Shapoval asserted that they observed a blue colouration of the melt containing molybdenum oxide, which seemingly arose owing to partial reduction of Mo03 to lower oxidation degrees of molybdenum with the simultaneous oxidation of chloride ions to chlorine, which evaporated from the melt. The molybdenum oxides formed were of the general composition Mo 03 i. 

The reaction (1.2.70) leads to a reduction of the equilibrium concentration of the acid (MoO +) in the KCl-NaCl melt that, in its turn, causes a shift of equilibrium (1.2.69) to the right. As a result, the [Mo03]/[MoC 4 ] ratio decreases, which results in a reduction in pO, as follows from the equation 

Despite the possibility of the simultaneous realization of these processes, the potentiometric curves of acid-base titration of Mo03 have no distinctive features as compared with the conventional ones [145]. However, the reverse titration curve differs appreciably from the direct titration results. Using the latter data the equilibrium constant of the formation of dimolybdate in the molten KCl-NaCl eutectic was calculated in Ref. [145] as 

The curve of the reverse titration contains an additional drop of e.m.f. (pO) that corresponds to a Mo03/Mo04 buffer system and allowed estimation of the equilibrium constant of the following reaction as K = 880 880. 

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