Study of Stability Constants of Complexes of some Divalent Metal Ions and Rare Earth Metal Ions with 5-Benzal-3- phenyl-2-thioxo-4-imidazolidinone.

Physical Chemistry Laboratory, Institute of Science, Bombay-400 032 Manuscript received 26 December 1984, revised 7 October 1985, accepted 2 December 1985 The stepwise stability constants of complexes of 5-benzal-3-phenyl-2-thioxo-4-imida­x)lidinone with CuIl, ZnII, NIII and CdII as transition metal ions and SmII. GdIII, and DyIII, as rare earth metal ions are determined by Calvin-Bjerrum potentio­metric titration method. The study was conducted in 3 : 1 (v/v) dioxane-water medium at ionic strength 0.1 µ and temperature 27± 1°. The order of the stability constants is found to be in agreement with the order reported by earlier workers. In case of rare earth metal ions, the stability constants observed are slightly lower as compared to the divalent metal ions studied, thereby indicating lesser ionic character