Thermodynamic dissociation constant studies of caffeine at different temperatures and in organic water solvent mixture.

Thermodynamic dissociation studies have been carried out potentiometrically at various temperatures from 25 to 50 degrees C and in 10, 20, 30 and 40% v/v dioxane-water solvent mixture at 25 degrees C. The influence of temperature and nature of solvent on dissociation equilibria of caffeine is being investigated. A computer program in GW-BASIC has been used to calculate the pK values.

Determination of equilibrium constant of ascorbic acid and benzoic acid at different temperature and in aqueous and non-aqueous media.

Dissociation constant studies of ascorbic acid and benzoic acid has been carried out potentiometrically at various temperature from 25 to 50 degrees C and in 10, 20, 30 and 40 percent dioxane-water solvent system at 25 degrees C. Effect of temperature and solvent concentration on pKa values has been observed. The resolution of acid strength in dioxane-water relative to that in water has been determined for both compound by plotting pKa values vs percent composition of solvent. The results shows greater resolution in non-aqueous media as compare to aqueous media. Data obtained is analyzed by Computer program written in GW-Basic for calculation of pKa values for monobasic acid.