A MICROCOLORIMETRIC METHOD FOR THE DETERMINATION OF CITRIC ACID

Kometiani, in 1931 (l), developed a titrimetric method for the macrodetermination of citric acid (4 to 40 mg.) based on the reaction of warm alcoholic solutions of organic bromides with sodium or potassium iodide, which had been described by Finkelstein in 1910 (2).Citric acid was first oxidized and brominated to pentabromoacetone.The pentabromoacetone which precipitated quantitatively was filtered off and dissolved in alcohol, to which acetic acid was added to favor the substitution of bromine by iodine.The alcoholic solution was then heated to just below boiling on a water bath, with the addition of an alcoholic solution of sodium iodide.The iodine liberated n-as titrated with sodium thiosulfate.The reaction between pentabromoacetone and sodium iodide in acid solution is believed to take place as shown in the accompanying scheme.