Ionisation Constants of some Heterocyclic Thioureas in some Mixed Solvents and at different Ionic Strengths and Temperatures

Q. E. Unit of CTRL (ICAR)

Department of Plant Breeding, Haryana Agricultural University, Hisar-125 004

D. N. (P. G.) College, Meerut

Manuscript received 2 January 1989, revised 28 September 1989, accepted 26 July 1990

Acid dissociation constants of some substituted heterocyclic thioureas have been determined potentiometrically in aqueous ethanol (75% v/v) at different ionic strengths and thermodynamic dissociation constants have been calculated from these data. Ionisation constants at fixed ionic strength (0.1 mol dm^-3) over the temperature range (10-50˚) and in different solvent-water systems have been determined. The thermodynamic parameters have been evaluated and effect of dielectric constants on dissociation constant have been discussed.