Electrometric studies on formation of cerium vanadates as a function of pH

Abstract

The precise nature of the reaction between nitric acid and sodium ortho-vanadate solutionshas been studied by means of electrometric techniques involving potentiometric and conductometrictitrations. The well defined inflections and breaks in the titration curves confirm the existence of theanions, pyro-V 2 O 74- , meta-VO 3- and poly-H 2 V 10 O 284- corresponding to the ratios of VO 43- :H + as 1:1,1:2 and 1:2.6 in the neighborhood of pH 10.5, 7.4 and 3.6, respectively. The interaction of cerium(III)nitrate with sodium vanadate solutions, at specific pH levels 12.4, 10.5, 7.4 and 3.6 was also studiedby potentiometric and conductometric titrations between the reactants. The end-points obtained fromthe sharp inflections in the titration curves provide definite evidence for the formation and precipita-tion of cerium ortho-Ce 2 O 3 .V 2 O 5 , pyro-2Ce 2 O 3 .3V 2 O 5 and meta-Ce 2 O 3 .3V 2 O 5 vanadates in the neigh-borhood of pH 7.4, 6.2 and 4.8, respectively. Analytical investigations on the precipitates formed con-firm the results of the electrometric study.