Thermodynamic parameters of some Schiff bases derived from 5,7-dihydroxy-6-formyl-2-methylbenzopyran-4-one

Potentiometric studies on Schiff bases derived from 5,7-dihydroxy-6-formyl- 2-methylbenzopyran- 4-one were carried out at different ionic strengths (0. 02, 0.04, 0.06, 0.10 and 0.14 M NaCl), at different temperatures (25, 35, 4 5 and 55 degrees C) and in ethanol-water media of varying compositions (60, 70, 80 and 90% v/v). The ionization constants of the Schiff bases were inv estigated in the presence of different organic solvents (70% v/v), e.g. met hanol, ethanol, n-propanol, isopropanol, acetone, DMSO and DMF-water media. The thermodynamic parameters (Delta G, Delta H and Delta S) were also calc ulated.