Potentiometric Studies on the Complexes of Some Transition Metal lons and Rare-Earth Ions with 3 - Phenyl-2-thio-2,4, (1H, 3H) quinazolinedione

Physical Chemistry Laboratory, Institute of Science, Bombay-400 032

Manuscript received 5 October 1983, accepted 30 May 1984

Complexation equilibrium of metal complexes of Cu^I I, Zn^{l I}, Cd ^{I I}, Ni ^{I I}, Mn^I I and rare-earth metals. like Nd ^{I I I} Sm ^{I I}, Gd^{I I I} and Dy^{I I I} with 3-pbenyl-2- thio--2,4, (1H, 3H) quinazolinedione have been studied Potentiometrically. The proton dissociation constant of the reagent and the dissociation constant of its metal complexes have been determined by Celvin pH titration technique as adopted by Irving and
Rossotti at 27±0.1° and at ionic strength, \(\mu\)=-0.1M in 3:1 (v/v) dioxane·water medium. The order of stability constants of the complexes is found to be Cu ^{I I} >Cd ^I I > Ni ^I I > Zn^{l I} > Mn ^{I I} The stability constants in case of rare-earth metal ions have been investigated only to know their ionic character