Membrane self‐diffusion coefficients for sodium ion, cesium ion, and water have been measured for Nafion® 120 perfluorosulfonate ion exchange membranes. Values have been determined as a function of temperature, and as a function of membrane water content by studying samples in heteroionic forms. The diffusional properties of this polymer are found to differ from those of conventional polystyrenesulfonates in several respects, and the free volume theory which describes ionic diffusion in the latter is inappropriate to treat Nafion. Results indicate that cations may exist in two distinct regions in the polymer; the proportion of total cations in each region may depend on the ions size and charge density. A structural model of Nafion, which correlates the membrane's spectroscopic and diffusional properties, is proposed to explain the results.

may be possible to predict the extent of stacking of purines and pyrimidines in aqueous solutions from retention data. Futher work is now being carried out to examine these postulations.

an experienced technician to obtain reliable results using the Methylene Blue Method.The results from Table III indicate that chloride ion may be included as part of the precipitate, leading to a positive error.Chloride has also been reported to give a positive error with the Methylene Blue Method (4, 18). The interference of chloride on the results of surfactant analyses using quaternary ammonium salts needs further investigation. ACKNOWLEDGMENT The authors thank M. W. Listen for testing many of the electrodes and C. A. Pearson for the Methylene Blue data. LITERATURE CITED(1) C.

A Teflon test cell has been built to measure d-c membrane conductance in highly concentrated alkali metal hydroxide solutions at temperatures and pressures up to 200~ and 100 bar. The method allows these measurements to be conducted for membrane current densities up to 1.5 A-cm -~. The membrane voltage drop is determined using reference electrodes which are placed on either side of the membrane. Conductance data were obtained for Nation | perfluorinated sulfonate ionomer of 1150 equiv, wt in the temperature range of 100~176Results show a tenfold decrease in specific conductance when the solution concentration is increased from 5.0 to 10.0M sodium hydroxide solution.

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