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. Table 1 Maximum allowable content of the interfering elements Test portion Application ranges Δws % (m/m) % (m/m) Nb Si Ta Ti g 0,5 1,0 0,3 1,0 1,0 0,000 3 to 0,001 0 1,0 2,0 0,6 2,0 0,50 0,001 0 to 0,010