Abstract
4-(2-Pyridylazo)-resorcin (PAR) reacts with iron(II) to form a water-soluble red complex. It has an absorption maximum at 500 mμ and the absorbance is constant in the pH region from 8.8 to 10.3. The mole ratio of iron(II) and PAR in the complex is found to be 1 : 3 at pH 10. The molar absorptivity of the complex is 5.0×104, being about 5 times as large as that of the 1, 10-phenanthroline complex.
Majority of interfering metal ions in amounts 25 to 100 times that of iron are completely masked by adding L-ascorbate and thiourea preliminarily to the sample solution and by adding EDTA and potassium cyanide after the PAR-iron(II) complex formation is completed. The masking effect was scarcely observed for nickel and cobalt in concentrations comparable to that of iron. This method may be successfully applied to the determination of traces of iron not only in water but also in alloys of copper, tin etc.
