Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
Thermometric Titration in the Investigation of the Formation of Polyanions of Molybdenum(VI), Tungsten(VI), Vanadium(V), and Chromium(VI). III. Titration of Molybdic Acid with Sodium Hydroxide Solution
Nobutoshi KibaTsugio Takeuchi
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1973 Volume 46 Issue 10 Pages 3086-3090


To define the properties of molybdenum-containing species which appear in the acidification of neutral molybdate solution with mineral acid, the reverse process, i.e. the titration of molybdic acid of acidified molybdate solution with sodium hydroxide, was examined and the titration curves were obtained thermometrically as well as potentiometrically. In the thermometric titration curves there are inflections not found on the pH-titration curves of the same systems. Titration curves of both methods change with molybdenum concentration, the reaction process being found to be responsible for the change. Polymolybdate anions were identified with the aid of the ultraviolet spectrophotometry of Punger et al. A neutral salt such as sodium perchlorate or lithium perchlorate was found to affect the shape of the thermometric titration curve, since in the presence of such salt octamolybdate ion was readily converted into heptamolybdate ion.

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