Enthalpies of solution of selected electrolytes in sulfolane and in acetonitrile

An isoperibol solution calorimeter has been employed to measure enthalpies of solution of selected alkali metal and tetraalkylammonium halides in sulfolane at 30.00 OC and in acetonitrile at 25.00 OC. Enthalpies of solution have also been measured for NaC104 in sulfolane. Al l measurements were made at concentrations <0.01 m and have been corrected to standard state conditions. Within limits of experimental error the concentration dependence of the data agrees with the calculated Debye-Huckel limiting slopes. Sulfolane exhibits a negative limiting slope, which, to the authors' knowledge, is the first time a pure solvent showing this characteristic has been reported. Standard enthalpies of transfer of the electrolytes from acetonitrile (AN) to sulfolane (TMS), AHOTMS--AN, are negative for all electrolytes examined, except for lithium salts, which exhibit large positive values for AHOTMS. A ~ . The results are discussed in terms of the suitability of the solvents for use as reference solvents.