On vanadates. I. Colorimetric Studies on Orange Vanadates

Colorimetric studies of the systems metavanadate‐acid indicate the formation of the same hexacondensed orange vanadate ion (HV 6 O 17 ) 3− , independent of the nature and concentration of the reactants according to the following equation:\documentclass{article}\pagestyle{empty}\begin{document}$$\begin{array}{l} 2({\rm V}_{\rm 3} {\rm O}_{\rm 9})^{3 - } + 3{\rm HX = (HV}_{\rm 6} {\rm O}_{{\rm 17}})^{3 - } + 3{\rm X}^{\rm - } + {\rm H}_2 {\rm O,} \\ {\rm where X}^ - = {\rm ClO}_{\rm 4}^{\rm - },{\rm Cl}^{\rm - },{\rm F}^{\rm - },{\rm CH}_{\rm 3} {\rm COO}^{\rm - },{\rm ClCH}_{\rm 2} {\rm COO}^{\rm - } \\ \end{array}$$\end{document}Except the (HV 6 O 17 ) 3− ion, no indication of any other orange vanadate species could be found. The hexacondensed orange vanadate ion has been found to be the most coloured and highest polymerised species of all the vanadates. The hydrolytic dissociation constant for (HV 6 O 17 ) 3− ion has been found by J OB 's method of continued variation to be 4.26 · 10 −17 . The tricondensation of metavanadate ion has been supported from the data obtained in the present work. The colour of orange vanadate has been found to approximately obey Beer's law in the concentration range 10–45 p. p. m. of vanadium.