This document specifies a thiocyanate spectrophotometric method for the determination of the molybdenum contents in steel and iron. The method is applicable to molybdenum mass fractions between 0,005 % and 0,125 %. Vanadium and tungsten interfere with the measurement if, because of their contents, the V/Mo ratio is greater than 16 or the W/Mo ratio is greater than 8 (see NOTE). NOTE Greater V/Mo or W/Mo ratios (up to 300) may, however, be permitted, but in such cases it is necessary to carry out the measurement very quickly after the extraction.