SPECTROPHOTOMETRIC DETERMINATION OF IRON(III) WITH 3-((2-HYDROXYPHENYL)DIAZENYL)PENTADIONE-2,4 AND DIANTIPYRYLMETHANE

The complex formation of iron(III) with 3-((2-hydroxyphenyl)diazenyl)pentadione-2,4 and diantipyrylmethane was investigated by spectrophotometric method and highly selective method of determination of its microamounts in natural objects established. It's found that at pH 2.0–2.5 in the presence of diantipyrylmethane Fe(III) forms with reagent intensively colored mixed-ligand complex Fe(III)–R–DAM with the ratio of components 1:2:1. During formation of mixed-ligand complex bathochromic shift and hyperchromic effect are observed compared to binary complex. The optimum conditions of formation of same and mixed-ligand complexes of Fe(III) were determined and the main spectrophotometric characteristics calculated. By spectrophotometric method stability constants of complexes are determined and found that mixed-ligand complex Fe(III)–R–DAM has high stability: lgβ(Fe–R)=5.76±0.10; lgβ(Fe–R–DAM)=14.65±0.26. The new highly selectivity spectrophotometric method for the determination of iron(III) has been developed and applied for the determination of its quantity in volcanic mountain rocks. Keywords: