POLAROGRAPHY IN SULFOLANE AND REFERENCE OF POTENTIALS IN SULFOLANE AND OTHER NONAQUEOUS SOLVENTS TO WATER SCALE

A procedure for the purification of sulfolane was developed, and tests were applied for certain classes of impurities. A study of the polarographic properties of the alkali metal ions showed that the current at short drop life is anomalously low, but normal at longer times. This phenomenon is attributed to a depletion effect resulting from the high viscosity of sulfolane. Potentials in sulfolane are referred to the water scale by a procedure based on the representation of the relative polarographic half-wave potentials of the alkali metals in sulfolane and in water by a modification of the Born equation. It is estimated that the standard reduction potential of rubidium ion in sulfolane is 0.11 V more positive than in water and 0.06 V more negative than in acetonitrile, both values including a correction for the difference in solvent molality. These results are compared with those for several other nitriles and acetone. It appears that the magnitude of the liquid junction potential between the aqueous saturated calomel electrode and 0.1 M solutions of tetraethylammonium perchlorate in sulfolane, the nitriles or acetone does not exceed a few hundredths of a volt. Qualitative observations are made for several other solvents. Some of the uncertainties in this and other procedures that have been used for the comparison of potentials in different solvents are discussed. © 1969, American Chemical Society. All rights reserved.