than those obtained with the samples from the meteorites, but is typical of the performance obtained with the detector in this work. CONCLUSIONSEvaluations of the photoionization detector developed indicated it to be a highly sensitive and discriminating device of considerable long-term stability. The end of the hollow discharge cathode was clean even after approximately 500 hours

Publication costs assisted by Eastman Kodak CompanyRelationships between the permeability of a solvent-containing polymer membrane to a solute and the amount of polymer present in the membrane have been derived by Yasuda, et ai, and by Mackie and Meares. Yasuda and coworkers considered the influence of the free volume in the membrane on permeability, whereas Mackie and Meares related diffusivity in the membrane to the tortuosity present and then described a relationship between the tortuosity and the volume fraction of polymer (02). Data are presented which show that, for low-molecular-weight permeants (such as ethylene glycol and ethanol) in moderately to highly water-swollen membranes from gelatin and poly(vinyl alcohol), both the Yasuda and the Mackie-Meares equations agree reasonably well with experimental data. In the 02 range studied here (0.08 < l>2 5 0.59), the Mackie-Meares equation is the better approximation. Also, the Mackie-Meares equation can be used to describe the permeabilities of different kinds of membranes, including those with very low tortuosities, because it considers explicitly tortuosity as a variable.

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synopsisThe well-known interaction between Congo Red and poly(viny1 alcohol), PVA, was studied by equilibrium dialysis. The diffusion of Congo Red into PVA membranes was much more rapid in 0.1N NaCl solution than in water. The dye appeared to be practically immobilized by the membranes in both solvents. A short survey of the dialytic behavior of various classes of ionic dyes through PVA membranes with water as solvent was undertaken. Anionic dyes permeated the membranes only very slowly, whereas cationic dyes permeated the membranes relatively rapidly and dyed them considerably. The existence of negative charges on the PVA membranes was demonstrated by performing dialysis experiments with the anionic dye Orange I1 and the cationic dye Acridine Orange in water and in excess electrolyte (1N NaCl).