Combustion spectrophotometric determination of sulfur in iron, steel and ferroalloys

A sample of iron, steel or ferroalloys was taken in a combustion boat, and was heated at 1450°C passing oxygen gas to convert sulfur into sulfur dioxide. The dioxide was absorbed into 0.2M Na2HgCl4 solution, and determined photometrically with formalin and p-rosaniline by measuring the absorbance at 550 mμ after 20 min. standing. Vanadium pentoxide was used as a combustion aid giving satisfactory result with an almost complete prevention of the spattering of oxides. The molar extinction coefficient of the color was 44, 000, and the linear relation was obtained over the range 035 μgS/100 ml. The reproducibilities of the method represented as relative standard deviation were 5.4% for carbon steel with 0.015% S and 7.0% for ferrotungsten with 0.010% S. Rapid determination of 0.0040.070% sulfur was carried out with good accuracy.