Author:
Brewer D. G.,Page John A.
Abstract
The polarography of alizarin alone, and alizarin in the presence of magnesium, has been studied in an ammonia–ammonium chloride electrolyte. Alizarin was found to give a reduction wave with E1/2 = −(0.14 + 0.059 pH) volts vs. S.C.E. and a polarographic diffusion coefficient D, equal to 1.20 × 10−6 cm2 sec−1over a range of pH from 7.4 to 10.0 in aqueous solution at 25 °C. The slope of the wave corresponded to a two-electron reversible process. The addition of magnesium caused a decrease in the polarographic wave for alizarin, but the combining ratio of magnesium to alizarin was a function of pH, ranging from 1.02 at pH 9.0 to 1.28 at pH 10.1. The combining ratio greater than unity could be attributed to alizarin adsorbed on a 1:1 (MgAlz) precipitate. The removal of alizarin from the solution was not quantitative in the presence of excess magnesium, and there is evidence of the formation of soluble complex species. The reaction is potentially useful for the indirect polarographic determination of magnesium.
Publisher
Canadian Science Publishing
Subject
Organic Chemistry,General Chemistry,Catalysis
Cited by
3 articles.
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