Composition and Stability of lndium(III)-Chrome Azurol S Chelate

The formation of a, pink-coloured chelate ($\lambda$$max$ 530 mµ) between indium(III) and trisodium loft of sulphodichlorohydroxydimethylfuchvon dicarboxylie acid (chrome Azurol S) has been reported. The chelate(M:Ke=1:1) is stable between $p$H 3.5 and 5.5. The value of log K (stability constant) is 4.4 at $p$H 4.0 (25°) Chelation is suggested to occur between the phenolic oxygen and adjacent carboxylic oxygen.