Ionization Constant of Ferron in Mixed-Solvents

Department of Chemistry, Post-Graduate Centre, Osmania University, Warangal-1, (A.P.)

Manuscript received 31 October 1972; revised 25 June 1973: accepted 27 June 1973

The ionization constant of Ferron, 7-lode 8-hydroxy quinoline 5-sulphonic acid (sodium salt) have been studied by potentiometric method in methanol-water, ethanol-water, isopropanol­water, acetone-water, 1,4-dioxaue-water, glycol-water and glycerol-water mixtures at constant ionic strength of 0.1 M KNO₃ at 25°, 35° and 45°. The variation of pK₁ with inverse dielectric constant gave a linear relationship from which the mean radii of dianion were calculated in the above solvents. From the variation of pk₁ with temperature ΔH, ΔS, and ΔG values were cal­culated in iso-composition mixtures. A plot of ΔH versus ΔS gave a straight line from which the isokinetie temperature was calculated as 181°K.