This international Standard specifies a 1 ,lO-phenanthroline spectrometric method for the determination of iron in water and waste water. Procedures are described for the determination of a) total iron (sum of dissolved and undissolved iron) : 1) direct determination, 2) determination after decomposition; b) total dissolved iron [sum of dissolved iron(ll) and iron(lll)]; c) determination of dissolved iron( 11). The methods are applicable to the determination of iron concentrations between 0,Ol and 5 mg/l. Iron concentrations above 5 mg/l may be determined after suitable dilution of the Sample. For interferences see clause 10.