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Soil Science Society of America Journal Abstract -

Colorimetric Determination of Iron of Mixed Valency by Orthophenanthroline1


This article in SSSAJ

  1. Vol. 30 No. 5, p. 663-664
    Received: Apr 25, 1966
    Accepted: June 7, 1966

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  1. G. S. R. Krishna Murti,
  2. V. V. Volk and
  3. M. L. Jackson2



A colorimetric method for the determination of Fe in a mixed Fe3+ and Fe2+ valency system has been proposed. Complete reduction of Fe3+ to Fe2+, which was essential for the formation of a stable colored complex with orthophenanthroline, was obtained when the iron solution, buffered at pH 3.5 with sodium acetate, was heated for 1 hr at 65C with 5% hydroxylamine hydrochloride. This reduction procedure was found to be suitable even for solutions at a higher pH where iron was present either as Fe3+ or as a hydroxylated complex. The organe color complex was found to be stable at pH values 2 to 9 for at least 20 hr and no interference of citrate ion was observed in the stability or the formation of the color.

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