Potentiometric Studies on La(III), Ce(III), Pr(III), Nd(III), Sm(III), Gd(III), Tb(III), Dy(III), Ho(III) and Y(III) Complexes of Tiron

Department of Chemistry, Kurukshetra University, Kurukshetra-132 119 Manuscript received 23 October 1979, accepted 30 December 1979 The formation constants of 1:1, 1:2 and 1:3 complexes of Las3+, Ces3+, Pr3+, Nd3+, Sm3+, Gd3+, Dy3+, Ho3+, and Y3+ with Tiron have been studied potentiometrically in aqueous medium at different ionic strengths (0.05, 0.1, 0.15 and 0.2M KNO3) and temperatures (25° and 35°) using Calvin-Bjerrum titration technique as modified by Irving and Rossotti. In general the stability sequence follows: Ho3+ > Dy3+ > Y3+ > Tb3+ > Gd3+ > Sm3+ > Nd3+ > Pr3+ > CO3+ > La3+. The thermo- dynamic stability constants, log \( K_1^μ\)=0 and log \( K_2^μ\)=0, have been determined by extrapolating the values to zero ionic strength. The thermodynamic functions (∆G, ∆H and ∆S) accompanying complex formation have also been reported