Palavras-chave
Cerium(III)
Electrometry
Como Citar
Resumo
The course of reaction between cerium(III) nitrate and different sodium tungstates (Na2WO4, Na10W12O41 and Na6W12O39) has been followed by means of pH and conductometric titrations between the reactants at different pH levels, in aqueous and alcoholic media, with each of the reagents alternatively used as titrant. The electrometric experiments provide definite evidence of the formation of normal-Ce2O3.3WO3 and para- 5Ce2O3.36WO3 tungstates of cerium in the vicinity of pH 6.2 and 5.3. The formation of normal tungstate is almost quantitative and the pH titrations offer a simple means for determination of cerium(III) or tungstate solutions at suitable concentrations and pH range.
Referências
COTTON, F.A., WILKINSON, G. Advanced inorganic chemistry, 3rd ed. New York: Interscience, 1972. p.952. [ Links ]
CRAIG, H.R., TYNEE, S.Y. Equilibria of isopolytungstates in aqueous acidic solutions Inorg. Chem., v.4, p.997, 1965. [ Links ]
GRAYSON, M. (Ex. Ed.), Kirk-Othmer Encyclopedia of Chemical Technology. 3rd. ed. New York: Wiley-Interscience, 1993. v.23, p.431. [ Links ]
HUDSON, M. Tungsten: Its sources, extraction and uses. Chem. Br., v.6, p.438-42, 1982. [ Links ]
KEPERT, D.L. Isopolyanions and heteropolyanions. In: TROTMAN-DICKENSON, A.F. (Ex. Ed.) Comprehensive Inorganic Chemistry, vol. 4, Oxford: Pergamon, 1973. pp. 641, 642, 646. [ Links ]
MACINNIS, M.B., KIM, T.K. The impact of solvent extraction and ion exchange on the hydrometallurgy of tungsten and molybdenum. J. Chem. Tech. Biotechnol. v.29, p.225, 1979. [ Links ]
POPE, M.T., DALE, B.W. Isopoly-vanadates, -niobates, and –tantalates. Q. Revs., v.22, p.527-48, 1968. [ Links ]
PRASAD, S. Electrometric studies of an acid-thiomolybdate system and the formation of isopolyanions. Ci. Cult., v.32, p.1665-8, 1980. [ Links ]
PRASAD, S. Thiotungstate isopolyanions: An electrometric study. Can. J. Chem., v.59, p.563-5, 1981. [ Links ]
PRASAD, S. Tungstate isopolyanions: An electrometric study. Quím. Nova, v.17, n.1, p.31-4, 1994. [ Links ]
PRASAD, S., BARROS, J.V. Electrometric studies on uranyl molybdates as a function of pH. Ecl. Quím. (São Paulo), v.23, p. 59-70, 1998. [ Links ]
PRASAD, S., BRITO, A.L.F., BRITO, J.B. Electrometric studies on formation of chromium(III) tungstates as a function of pH. Orient. J. Chem., v.15, n.3, p.427-32, 1999. [ Links ]
PRASAD, S., GONÇALVES, S.B., BRITO, J.B. Electrometric studies on the system acid-vanadate and the formation of heavy metal vanadates. Catal. Today, v.57, p.343-52, 2000. [ Links ]
PRASAD, S., GUIMARÃES, T.L.M. Electrometric investigations on the system acid-molybdate and the formation of heavy metal molybdates. J. Braz. Chem. Soc., v.9, p.253-9, 1998. [ Links ]
STANDEN, A. (Ex. Ed.) Kirk-Othmer Encyclopedia of Chemical Technology, 2nd ed. New York: Interscience, 1967. v.13, p.782. [ Links ]
VOGEL, A.I., A textbook of quantitative inorganic analytical chemistry, 3rd. ed. London: Longmans, 1968. p.(a) 567, (b) 324. [ Links ]
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