Simultaneous Spectrophotometric Determination of lron(III) and Aluminium(III) with 2-Carboxy-2'-Hydroxy-3',5'  Dimethylazobenzene-4-Sulphonic Acid.

Department of Chemistry, Nagpur University, Nagpur 440 010

Manuscript received 21 May 1976 ; accepted 15 July 1976

A spectrohotometric method is developed for the simultaneous determination of Fe(III)and Al(III) in the mixture and in ore, dolomite. 2-Carboxy-2'-hydyroxy-3', 5'- dimethylazobenzene-4-sulphonic acid (CHDMAS) forms complexes with Fe(III) and Al(III) at pH 4.0 which have maximum absorption at 620 nm (E 1275) and 510 nm (E=2855) respectively. Fe(III)-CHDMAS complex obeys Beer's law in the concentration range of 0.5-4.0 ppm at 620 nm and 1.0-8.0 ppm at 510nm, whereas Al(III)-CHDMAS complex holds Beer's law in the range of 0.5-2.5 ppm at 620 nm and 0.1-2.0 ppm at 510 nm. The concentration of these eleme its in an unknown mixture or in the ore, dolomite can be determined from the following equations :

         [Fe]10⁴=9.988 x A₆₂₀-3.111 X A₅₁₀

and  [Al] x 10⁴=4.466 X A₅₁₀-3.179 X A₆₂₀

The standard deviation of the method is ±0.62% and ±0.82% in the determination of Fe(III) and AI(III) respectively.