Potentiometric Studies of Stepwise Chelate Formation of Fe(III), Co(ll), Ni(Il), Cu(ll) and Mn(II) with VanillinAnthranilate (Van-An)

Chemical Laboratories, M. L. B. Girls College, Bhopal-462 001

Manuscript received 4 January 1984, accepted 25 March 1984

Interaction of vanillin-anthranilate (Van·An) with some transition metal ions, Fe(III), Co(ll), Ni(II), Cu(II) and Mn(ll) in 20% aqueous ethanolic solution has been studied potentiometrically. Stepwise proton-ligand and metal-ligand formation constants have been evaluated at 30 and 40° and at a fixed ionic strength of 0.1M KNO₃. The thermodynamic parameters, \(\bigtriangleup\)G, \(\bigtriangleup\)H and \(\bigtriangleup\)S evaluated at 30^o and 0.1 M KNO₂ ionic strength show that the reaction of Van-An in solution with these metal ions is an endothermic reaction and entropy change plays an important part in giving the observed order of stability as Fe(III) >Cu(II)> Ni(ll) > Co(ll) > Mn(ll).