This document specifies a spectrophotometric method for the determination of phosphorus in steel and iron. The method is applicable to phosphorus contents between 0,001 0 % (mass fraction) and 1,0 % (mass fraction). Arsenic, hafnium, niobium, tantalum, titanium and tungsten interfere in determining phosphorus, but the interferences can be partially overcome by formation of complexes and use of small quantities of test portion. Depending on the concentration of the interfering elements, the application ranges and test portions given in Table 1 apply. The lower end of the application range can only be reached in test samples with low contents of the interfering elements.