Salicylic acid derivatives form stable complexes with scandium(III) ion in aqueous solution

The stability constants of 5-nitrosalicylic acid (5-NSA) and 5-sulfosalicylic acid (5-SSA) complexes of Sc(III) were determined by potentiomeric pH titration. ML and ML2 type first and second complexes were observed in the solutions of 5-NSA and 5-SSA with Sc(III) at 25 degrees C in I=0.1 M ionic medium. The stability constants of Sc(III)-5NSA and Sc(III)-5SSA systems were also investigated by spectrophotometry to determine the stoichiometries of the complexes formed in the reactions. Our results showed that Sc(III)-5SSA complexes are more stable than the Sc(III)-5NSA completes in aqueous solutions.