Sulfolane concentration, conductance

Here, c is the total concentration of MA, KA is the association constant, a is the degree of dissociation of the ion-pair M2+A2h and y is the average activity coefficient of free ions of concentration ca. Because the ion-pairs do not conduct electricity, the molar conductivity A in the presence of ion association is less than in its absence. In Fig. 7.1, the difference between the experimental molar conductivity (A) and the value calculated from Eq. (7.1), /lcai, are plotted against c1/2 for lithium halides in sulfolane [la]. For Lil, the difference between A and /lcai is small because ion association is not appreciable (KA=5.(> mol-11). For LiBr (KA = 278 mol-11) and LiCl (KA= 13860 mol-11), however, A is much smaller than... 

Materials. Sulfolane (99%purity) (Aldrich) was treated with calcium hydride and distilled under reduced pressure. The freshly prepared solvent had a specific conductivity of 1.0 X 10 7 O"1 cm"1 and a residual water content of 8 X 10"3M as determined by Karl Fisher titration. Conductivity water and reagent grade ether (Baker) were used. Glacial acetic acid (CIL), trifluoroacetic acid (Baker), and trifluoro-methanesulfonic acid (3M) were used as received. All these acids had a minimum purity of 99.5% as determined by titration with standard sodium hydroxide. Methanesulfonic acid (Eastman), distilled under reduced pressure, had a purity of 99.6%. Sulfolane solutions of these acids were prepared by weight, and the acid concentrations were checked by acidimetry after the samples were flooded with water. The solutions... 

Figure 3. Specific conductance of sulfolane solutions of acids as. a function of water concentration at 30°C ( ), 0.54M HCFsCOt (A), 0.53M HCH3SOs (Q), 0.50M HCF SOs (O),...

Specific conductivity of nitronium tetrafluoroborate varies linearly with concentration. Cryoscopic measurements in sulfolane solution indiate that the nitronium salt is present as ion pairs and the conductance must be due to ion triplets and not separated ions [54]. 

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