Spectrophotometric investigation of the Fe(III)-disulphonate hydroquinone complex

Iron(III) form an indigo-blue complex with the disulphonated product of hydroquinone (K 2 S 2 Hy) in acid media with an absorption maxima at 600 nm. The time stability of the complex, dependence of the complex absorbance onpH and the influence of temperature and solvent were followed on the basis of spectrophotometric measurements. Using the Job, mole ratio and Henry-Franck-Ostwald methods, the composition and relative stability constant of this complex, in 80 vol.% ethanol as solvent, were determined (1:1; log β'293 = 3.37). Anew spectrophotometric method for the determination of iron has been developed and the calibration curve is linear in the concentration range from 0.65 to 6.45 μg cm - 3 . The effects of foreign ions on the determination of iron were investigated in order to assess the selectivity of the method. The method was applied for the determination of Fe(III) in the natural juice of beet.