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Zeitschrift für Naturforschung B

A Journal of Chemical Sciences

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Volume 30, Issue 7-8


Die Komplexbildung der Zitronensäure, II.

Komplexbildung zwischen Zitronensäure und Eisen(III) / The Formation of Complexes of Citric Acid, II The Formation of Complexes of Citric Acid with Iron(III)

Josef A. Veith / Günther Wiese
Published Online: 2014-06-02 | DOI: https://doi.org/10.1515/znb-1975-7-820

Mixtures of citric acid (H3Ci) and Fe(NO3)3 with variable molar ratios (H3Ci/Fe(NO3)3 from 0 to 2.55) were titrated with NaOH. The change in pH and the occurring inflection points were registered with a potentiograph (Fig. 1). For each inflection point (I.P.) the existing H3Ci/Fe(NO3)3 molar ratio was plotted against the NaOH/Fe(NO3)3 molar ratio which existed at the corresponding inflection point (at most three I.P. for each titration curve). The coefficients ej, fj and gj for each dehydrated

Fe-Ci-complex [Fefj(OH)gj-3ejCicj](gj-3fj)⁻ with j = 1, 2, . . . ,

could be calculated from the points of intersection (Pj) in the x-y-diagram (Fig. 2). Thus, the following three Fe-Ci-complexes were calculated:

From the 1st I.P. [Fe10(OH)18Ci5]3- with its maximum at pH ≃ 4.3.

From the 2nd I.P. [Fe5(OH)9Ci4]6- with its maximum at pH ≃ 8.0.

From the 3rd I.P. [Fe4(OH)11Ci]2- with its maximum at pH ≃ 10.1.

The range of their existence as functions of H3Ci/Fe(NO3)3 ratios (Fig. 3 and 4) and pH (Fig. 4) is discussed.

About the article

Received: 1975-05-15

Published Online: 2014-06-02

Published in Print: 1975-08-01

Citation Information: Zeitschrift für Naturforschung B, Volume 30, Issue 7-8, Pages 575–581, ISSN (Online) 1865-7117, ISSN (Print) 0932-0776, DOI: https://doi.org/10.1515/znb-1975-7-820.

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© 1946 – 2014: Verlag der Zeitschrift für Naturforschung. This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License. BY-NC-ND 3.0

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