Dasgupta, Samarendra and Sinha, Birendra Chandra and Rawat, N S (1983) Stepwise complexometric determination of calcium and magnesium in the presence of a high manganese and iron content using potassium hexacyanoferrate(II) as a masking agent. The Analyst, 108 (1292). pp. 1396-1401. ISSN 0003-2654

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A critical study has been made on the masking of manganese and iron by their precipitation as Fe2Fe(CN)6 and Mn2Fe(CN)6 with K4Fe(CN)6 in the presence of ascorbic acid and potassium chloride for the complexometric titration of calcium plus magnesium with EDTA at pH 10. The optimum acid concentration and temperature for the selective and quantitative precipitation of Mn(II) and Fe(II) hexacyanoferrates(II), which are granular and nonadsorbant metallochromic indicators, are found to be 1-2.5 N hydrochloric acid and 25-50°C, respectively. In a solution with an acidity of lower than 1 N, the hexacyanoferrates(II) of Mn(II) and Fe(II) coprecipitate calcium and magnesium hexacyanoferrates(ll). At 70°C, the amount of coprecipitation increases. Up to 68.75 and 19.60 mg of manganese and iron, respectively, can be successfully masked in complexometric titration. For the titration of calcium alone at pH 12, the interference of manganese and iron has been overcome by oxidising Mn(II) - TEA to Mn(III) - TEA, which is stable against KDTA titration with air bubbling. Iron forms a quantitative Fe TEA complex almost instantaneously at pH 12. A simple procedure has been devised for the titration of Ca + Mg with EDTA after masking manganese and iron with K4Fe(CN)6, a non-toxic reagent. For calcium, TEA alone is used for masking both manganese and iron.

Item Type: Article
Subjects: Microstructure and Characterization
Depositing User: Bidhan Chaudhuri
Date Deposited: 23 May 2016 09:49
Last Modified: 23 May 2016 09:49
URI: http://cgcri.csircentral.net/id/eprint/3375

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