PHYSICO-CHEMICAL STUDIES OF COMPLEX ACID. PART II. CONDUCTOMETRIC AND GLASS ELECTRODE TITRATION OF MOLYBDIO ACID SOL

Molybdic acid sol, prepared by the action of dilute hydrochloric acid on ammonium molyb­date solution, when dialysed free from Cl’ ion, has a composition of the solute corresponding to NH4H- [O(MoO3)4]. The id on dilution from 3.30 x 10-2 M-MoCO3 to 1.65 x 10-4 if-MoO3 gave conti­nually increasing value of pH. In the region of pH 3.8 to 4.5, the curve wee rather fiat and this has been ascribed to the disintegration of colloidal micelle of molybdic said to true solution containing simpler ions as HMoO4' etc. The dissociation constant of this acid ion HMoO4' has been calculated to be pH =5.33 from the potentiometrio titration curve of the sol with NaOH