POTENTIOMETRIC STUDIES ON THE BINARY COMPLEXES OF N-[TRIS(HYDROXYMETHYL)METHYL]GLYCINE WITH TH4-TRICINE BINARY COMPLEX(, CE3+, LA3+ AND UO22+ AND MEDIUM EFFECTS ON A TH)

The stability constants for Mn+-tricine binary complexes (1:1 and 1:2) , where Mn+ = Th4+, Ce3+, La3+, and UO22+, have been determined pH-met rically in aqueous media at 25 degrees C and in the presence of 0.10 m ol dm(-3) (KNO3). The binary Th-tricine (1:1) complex was studied in t he presence of different organic solvents as well as in the presence o f different ratios of dioxane and at different temperatures. The calcu lated stability constants have been discussed in terms of the nature o f both the metal ion and tricine. It is suggested that tricine may act as a tridentate as well as a bidentate ligand. Solvent basicity and p roportion in addition to the differences in stabilization of the free base by hydrogen bonding with solvent molecules as well as the electro static effect are the major factors responsible for the observed high stability of the Th-tricine binary complex. The thermodynamic paramete rs (Delta H, Delta G, and Delta S) for the formation of 1:1 Tn-tricine complex in the presence of 40% (w/w) dioxane at different temperature s (5-45 degrees C) were calculated.