Colorimetric determination of organic iodine using flask combustion

Abstract

A simple colorimetric method for determining organic iodine involving the flask combustion and the successive dilution of liberated iodine in a definite volume of hydrocarbon solvent has been investigated.An organic sample containing about 2mg of iodine was burnt in a dry oxygen flask and 3ml of toluene or xylene was pipetted to the flaring lip at the top of flask. The solvent was drawn into the flask by loosening the stopper because of a reduced pressure produced in the flask after combustion, and the flask was stood for 5 minutes for complete absorption of iodine in the solvent. Twenty milliliters of the same solvent was further pipetted to the flask and the absorbance of the solution was measured at 505mμ for toluene or at 500mμ for xylene.A statistic comparison showed that the substitution of above solvents by benzene gave higher standard deviation of analytical results (Table VI) probably due to its higher volatility.A presence of chlorine above 4% in the sample gave lower analytical results due to formation of ICI. Sulfur in the sample gave sulfuric mist in the flask which made the solution turbid. This interference was avoided by standing the flask for 1 hour after the combustion until the sulfuric mist sank to the bottom of the flask.