Spectrophotometric Studies of Gallium, Indium and Thallium Chelates with Solochrome Cyanine R

The formation of reddish violet coloured chelates between trivalent gallium, indium and thallium with sodium salt of o-sulfohydroxydimethyl fuchsone dicarboxylic acid(SCR) have been reported. By studying the absorption spectra of the chelates in the entire visible range at different pH values, it was ascertained that only one complex is formed in all the cases, The composition of the chelates have been determined by the Job's method of continuous variations,mole ratio and slope ratio methods using absorbance measurements. The chelates have the composition of 1 : 1. The stability constants of the chelates have been calculated by four different methods, viz. (a) the method of Anderson and coworkers modified by Dey and coworkers using equimolecular solutions, (b) method of continuous variations using non-equimolecular solutions, (c) method of mole ratio and (d) by using the values of molecular extinction cofficient. The average values of log K are 5.8, 5.5 and 5.1 for Ga(III)-SCR, In (III)-SCR and Tl (III)-SCR chelates respectively.