Publisher Summary This chapter discusses protonation, oligomerization, and condensation reactions of vanadate(V), molybdate(VI), and tungstate(VI). The elements vanadium, molybdenum, and tungsten in their high oxidation states form the stable oxyanions [VO4]3-, [MoO4]2-, and [WO4]2-. In aqueous solution, these ions are easily protonated and show a strong tendency to form polyoxoanions by oxygen bridging, and the release of water molecules. Depending on pH and concentration, a great variety of ions can form in each case, giving rise to complex systems of simultaneous equilibria, which have proved difficult to characterize with certainty. The molybdate(VI) system, in particular, needs further clarification regarding the existence of some polyions. More kinetic and thermodynamic data would also help to improve the understanding of these systems and lead to a general inclusive explanation of the mechanism of polyoxoanion formation. In this respect, new information about some structural preferences of the different metals in mixed polyoxoanions is a useful addition to known facts regarding polyoxometalate structures.

Protonation, Oligomerization, and Condensation Reactions of Vanadate(V), Molybdate(vi), and Tungstate(vi)

Mechanistic investigation of molybdenum blue method for determination of phosphate

This review critically evaluates the reported thermodynamic data on chromium metal, oxides, hydroxides, free aqueous ions, and hydrolysis species. Several discrepancies and inconsistencies have been uncovered and resolved to improve equilibrium calculations for chemical modeling and related engineering purposes. A revised set of data is derived from evaluation of electrochemical measurements, silver chromate solubility measurements, and auxiliary post-1980 data, reevaluation of earlier data, and reconsideration of the path for the thermodynamic network. The recommended thermodynamic values for Cr(cr), C , C , Cr , Cr2 , Cr2O3(cr), CrO3(cr), FeCr2O4(cr), CrCl2(cr), CrCl3(cr), and KFe3(CrO4)2(OH)6(cr) at 25 °C, 1 bar, and infinite dilution are given.

Critical Evaluation and Selection of Standard State Thermodynamic Properties for Chromium Metal and Its Aqueous Ions, Hydrolysis Species, Oxides, and Hydroxides

Publisher Summary The chemistry of isopolymolybdates and isopolytungstates has been an area of intense activity for several decades. Yet, even today one cannot claim that all the important processes occurring on acidification of a molybdate or tungstate solution have been elucidated. Numerous contradictory reports appearing in the literature right up to the present have repeatedly done more to confuse than to clarify the subject. Thus, it is hardly surprising that not a single textbook correctly describes the situation in acidified molybdate and tungstate solutions. The number of proposals for polyions occurring in such solutions is legion. With little exaggeration it may be said that there is no conceivable species that has not been proposed at some time or other. Much of the effort involved in this field consists in scrutinizing the experimental conditions, the evaluation of measurements, and the interpretations given in past and present publications. The large number of methods already used in these studies presents a further difficulty.

Isopolymolybdates and Isopolytungstates

Equilibria of chromate(VI) species in acid medium and ab initio studies of these species

: Preliminary results are reported for studies of the equilibra in polymolybdate solutions using the LETAC-ROP computer program.

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On equilibria in polymolybdate solutions

/pdf/equilibrium-studies-of-polyanions-7-the-first-step-in-the-vd3nr0aih2.pdf

Equilibrium Studies of Polyanions. 7. The First Step in the Acidification of WO2-; Equilibria in 3 M NaClO4 at 25 degrees C.

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Equilibrium Studies on Polyanions. 9. The First Steps of Acidification of Chromate Ion in 3 M Na(ClO4) Medium at 25 degrees C.

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Equilibrium studies of polyanions part 20, a recalculation of emf data on the reactions of h(+) and wo4(2-) in 3m na(clo4) at 25 degrees

/pdf/is-the-nernst-equation-applicable-to-silver-i-concentration-403wi29zyz.pdf

Yukiyoshi Sasaki

Papers

On equilibria in polymolybdate solutions

Equilibrium Studies of Polyanions. 7. The First Step in the Acidification of WO2-; Equilibria in 3 M NaClO4 at 25 degrees C.

Equilibrium Studies on Polyanions. 9. The First Steps of Acidification of Chromate Ion in 3 M Na(ClO4) Medium at 25 degrees C.

Equilibrium studies of polyanions part 20, a recalculation of emf data on the reactions of h(+) and wo4(2-) in 3m na(clo4) at 25 degrees

Is the nernst equation applicable to silver(i) concentration cells in fused nitrate medium