Spectrophotometric studies on the zirconium complex of 2-(3,6-disulfo-8-hydroxynaphthylazo)-1,8-dihydroxynaphtualene-3, 6-disulfonic acid

Abstract

A chromotropic azo dye, DSNADNS, prepared from chromotropic acid and 1-amino-8-naphthol-3,6-disulfonic acid has been found to produce quantitative precipitation of zirconium in acid medium. The blue-violet complex formed is insoluble in all organic solvents commonly used for solvent extraction work, but is soluble in a number of liquid organic bases and solutions of ammonium salts in water showing pink to violet colouration. Spectrophotometric studies as to the nature of the complex in pyridine, triethanolamine ammonium acetate, oxalate and carbonate solutions and the analytical possibility of these solutions have been made. The complex appears to decompose in pyridine, ammonium acetate and ammonium oxalate solutions, but it is fairly stable in ammonium carbonate and triethanolamine solutions. The absorbance peaks of the dye in these solutions occur at 500 and 520 nm respectively, while the complex in triethanolamine and ammonium carbonate both shows absorbance maxima at 540 nm. The solution of the complex in these two solvents obeys Beer's law within a concentration range 4 to 25 mg of zirconium per litre. The molar absorbance coefficients of the complex in triethanolamine and ammonium carbonate are respectively 686 and 823, which indicate poor sensitivity. The solution of the complex in the former solvent is more stable than that in the latter and an analytical procedure for the spectrophotometric determination of zirconium, with little interference from foreign ions, may be developed with ease in the triethanolamine solution.