Potentiometric Determination of Stability Constants of Trivalent Metal Ion Complexes with Di-p-tolyl-thiovioluric Acid

Abstract

Potentiometrie Determination, Stability Constants, Di-p-tolyl-thiovioluric AcidThe consecutive formation constants of 1:1, 2:1, 3:1 chelate species formed by the interaction of di-p-tolyl-thiovioluric acid (D-p-TOTVA) with the tripositive lanthanons and yttrium cations were determined potentiometrically at 0.1 /i (NaC104) at 30 i 1 °C, in 75% aqueous dioxan.The 1:1 formation constants (log A'i) for the complexes increase with the increase in the atomic number of the lanthanon (3), with a break at gadolinium.The results indicate that the ligand bonds bidentately to heavier lanthanons (smaller ionic radii). However, definite dentate character of bonding to lighter (larger ionic radii) lanthanons could not be established.