Potentiometric Studies in Solution of some Transitional Metal Ion and Rare Earth Metal Ion Complexes of 5-Benzal-3-methyl-2-thiohydantoin( 5-benzal-3-methyl-4-imidozolinone-2-thioxo)

Physical Chemistry Laboratory, Institute of Science, Bombay-400 032 Manuscript received 26 December 1984, revised 26 June 1985, accepted 31 July 1985 The stepwise stability constants of complexes of 5-benzal-3-methyl-2-thiohydantoin with transition metal ions and rare earth metal ions are determined by Calvin-Bjerrum potentiometric titration method. The work is conducted in 3 : 1 (v/v) dioxane-water medium of ionic strength 0.1 N and at temperature 27±1°. The order of 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