Organic Polarography

Wawzonek, S.

doi:10.1021/ac60085a012

Cited by 5 publications

(1 citation statement)

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“…The azo-hydrazo reaction has been shown to occur with azobenzene and its derivatives (5,6), although some doubt still exists as t o the reversibility of the reaction (7). T h e azo dyes, orange I1 and metanil yellow, are claimed to follow a two electron reduction on the basis of an n value calculated from the wave slope (2).…”

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The Polarographic Reduction of Amaranth

Mckeown¹,

Thomson²

1954

Can. J. Chem.

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Amaranth, a food color, has been studied polarographically over a pH range of 2.0 to 10.0 in aqueous solution and was found to give a well-defined wave, diffusion controlled and suitable for quantitative work. Irreversibility was indicated by the behavior of the half-wave potential to changes in pH and co~icentration. With pH, a direct relationship of -0.080 v. per pH unit held between pH 2.0 and 7.0, while with concentration, the half-wave potential was found to apparently vary directly with the logarithm of concentratioa. Using a coefficient of diffusion value obtained by coilductance measurements the value of n for the reaction was calculated to be 4, which corresponds to a ruptl~re of the azo group t o yield the corresponding amines.In connection with the work of this laboratory, a study of the polarographic behavior of the artificial food colors was begun with the object of determining the possible value for qualitative and quantitative analysis. This paper is the first of a series ancl describes the reduction of amaranth a t the dropping mercury electrode.A consideration of the formula of amaranth reveals that two liltely possibilities for reduction exist: ( a ) the azo group accepts two hydrogen atoms to form an hydrazo group, and (b) the azo group accepts four hydrogen atoms to yield the corresponding amines.Polarographic work on several con~pounds similar to amaranth suggests that the former reaction should take place. The azo-hydrazo reaction has been shown to occur with azobenzene and its derivatives (5, 6), although some doubt still exists as t o the reversibility of the reaction (7). T h e azo dyes, orange I1 and metanil yellow, are claimed to follow a two electron reduction lManuscript received J u l y 30, 1954.

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