The S. W. Polarographic Determination of Disulfide, Mercaptan and Free Sulfur in Petroleum Naphtha

Abstract

Abstract The application of square-wave polarography to the determination of small amounts of disulfide, mercaptan and free sulfur in a mixed solution of methanol, glacial acetic acid, and sodium acetate was studied. Disulfide, mercaptan, and free sulfur in concentrations below 10 ppm were easily determined in these mixed solvents. The derivative wave heights were proportional to the concentrations predicted by the theory of s. w. polarography. The effects of changes in solvent and in supporting electrolyte concentration, dissolved oxygen, and temperature were discussed. It was determined that concentrations of 2 vol% glacial acetic acid and 1.4 m sodium acetate were necessary to obtain a constant peak height. The temperature coefficients of disulfide, mercaptan and free sulfur were about 4.5 (first wave), 0.7 and 4.5% per degree respectively in the neighborhood of 25°C. The effect of the dissolved oxygen was removed by passing nitrogen through for 5 min.