THERMODYNAMIC PARAMETERS OF TRANSFER AND SOLUTION OF OXALIC-ACID IN DIMETHYLSULFOXIDE WATER MEDIA

The solubility measurements for oxalic acid in DMSO-H2O MiXtures have been performed at four temperatures (298.15, 303.15, 308.15 and 313.15 K) to calculate the thermodynamic parameters of solution and transfer of oxalic acid from water, as reference solvent, to DMSO-H2O mixed so lvent. The solubility data have been discussed in terms of the solubil ity parameters. A multiple linear regression method, known as the exte nded Hansen solubility approach, has been used to estimate the partial and total solubility parameters for oxalic acid. The activity coeffic ients of oxalic acid in water and mixed solvents have been calculated theoretically and found to be unity. The thermodynamic parameters of t ransfer of oxalic acid have been found to increase with increasing mol e fraction of DMSO. The electrostatic parts of the standard free energ ies of transfer for oxalic acid have been calculated theoretically. Th ese values increase with increasing DMSO content.