This International Standard specifies a methylene blue spectrophotometric method for the determination of sulfur in steel and iron. The method is applicable to sulfur contents between 0,000 3 % (m/m) and 0,010 % (m/m). However, niobium, silicon, tantalum and titanium interfere in the determination of sulfur. Depending on the concentration of the interfering elements, the application ranges and test portion masses given in table 1 apply.