Oxidation and Decarboxylation of Citrate in the Presence of Ferrous Iron

Abstract

ALTHOUGH a paper by Wieland and Franke in 1928¹ described the induced oxidation of several hydroxy-acids in the presence of oxidizing ferrous iron, citric acid was not specifically mentioned, and its reaction under these conditions appears not to be well known. We have observed that mixtures of sodium citrate and ferrous sulphate, shaken in air at 28° C. and pH 6.0, absorbed oxygen in excess of that required to oxidize the iron. At the same time carbon dioxide was evolved, and the quantities of carbon dioxide evolved and of excess oxygen absorbed were approximately equimolar. The amounts of excess oxygen (presumably consumed in the oxidation of the citrate), and of carbon dioxide, were proportional to the initial amount of ferrous iron. No reaction was observed in the absence of oxygen. The identification of the decomposition products of citrate, apart from carbon dioxide, was not attempted.