Rao, S. Bhanojee

Sant, B. R.

English

NOPR

INDIAN J. CHEM., VOL. 20A, FEBRUARY 19813. CuRRY, R. C. & MELLON,M. G., Analyt. Chem., 28 (1956),1567.4. SZABO,Z. G., BECK, M. T.' & TOTH, K., Mikrochim. Acta,(1958), 181.5. UEDA, 1., Shika Igaku, 32 (1969), 726; Chern. Abstr., 73(1970), 51984.6. YrSIMIRSKII,K. B. & VASILEV,V. P., Instability constants;of complex compounds (Van Nostrand, Princeton, NewJersey), 1960, 130.Mnaganese(IV) as an Analytical Reagent forDetermination of TelluriumS. BHANOJEERAO & B. R. SANT*Regional Research Laboratory, BhubaneswarReceived 19 April 1980; revised and accepted 6 June 1980A simple and rapid method for the estimation of telluriteusing excess manganese(IV) sulphate solution is reported.Manganese(IV) is reduced to manganese(llI) and the excessof the reagent is titrated with standard iron(II) solution.TELLUROUS acid and tellurites are not easilyoxidised and most of the methods for theirestimation are very old and involve addition ofexcess oxidant and back titration. Recently Mandaland Sant+? reported the preparation and utilizationof manganese(IV) sulphate as an oxidant. Ourpreliminary experiments revealed that Te(IV) iscompletely oxidised to Te(VI) in sulphuric acidmedium.Manganese(IV) sulphate solution was preparedand standardised as described earlier', For thepreparation of tellurite solution, potassium telluritewas dissolved in 0.01 N potassium hydroxide andstandardised with eerie sulphate.All other reagents used were of AR grade.212ITABLE1 - ESTIMATIONOF TELLURlTESulphuric acid Tellurite(M)molarityTaken Found6 0.07144 0.071448 0.07144 0.0714410 0.07144 00714412 0.07144 0.0714414 0.07144 Erratic16 0.07144 Erratic10 0.1169 0.116910 0.1754 0.175410 0.05845 0.0584Procedure -To an aliquot of tellurite solutionsulphuric acid was added to maintain an overallmolarity of 8-10. To this was added a known excessof manganese(IV) sulphate solution. After 15 minat room temperature the excess oxidant was titratedwith standard iron(ll) solution using ferroin as indi-cator. One millilitre of 0.1 N Mn(IV) sulphate solu-tion corresponds to 6.38 mg tellurium.Typical results for the estimation of tellurium aregiven in Table 1.The oxidation of tellurium(IV) by manganese(IV)is a two step process :2 Mn(IV) + Te(IV) = 2 Mn(III) + Te(VI)2 Mn(IlI) + Te(lV) = 2 Mn(II) + Te(VI)The first reaction is complete within 5-10 min atambient temperature and the second reaction is slowand is not complete even after 6 hr. However, whenexcess of manganese(IV) is present only the firstreaction takes place enabling the precise estimationof Te(IV). The principal advantage of the methodis its simplicity and accuracy.References1. MANDAL,S. K. & SANT,B. R., Talanta, 23 (1976), 485.2. MANDAL,S. K. & SANT,B. R., Indian J. Chem., 19A (1980),389.\

Mnaganese(IV) as an Analytical Reagent for Determination of Tellurium

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Mnaganese(IV) as an Analytical Reagent for Determination of Tellurium

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