SynopsisDiffusion coefficients and solubilities of methane in polyisobutylene have been measured a t four temperatures between 102 and 188°C. in the pressure range 23-341 atm. Diffusion coefficients extrapolated to atmospheric pressure range from 1.72 X 1 0 P cm.z/ sec. a t 102°C. to 1.5 X cm.2/sec. a t 188°C. corresponding to an activation energy for diffusion of 8.7 f 0.4 kcal./mole. Solubilities are small, about one molecule of methane for every forty carbon atoms in the polyisobutylene a t 300 atm. partial pressure of methane. Solubilities vary little with temperature, but show an apparent minimum between 127 and 188°C. With improved methods of data analysis, diffusion coefficients and solubilities have been recalculated from previously reported studies on nitrogen in branched polyethylene and methane in branched polyethylene, linear polyethylene, and polystyrene. Recalculated diffusion coefficients are essentially the same as those reported previously, but the recalculated solubilities are decreased from 2 to 30%. The solubilities of all five systems show strong deviations from Henry's law, i.e., increases in partial pressure of methane and nitrogen with respect to solubility exceed linearity. Thc partial pressure (or fugacity)-solubility data may be interpreted in terms of a sorption model in which sorbed molecules are accommodated in widely dispersed, unoccupied volumes or sites in the polymer. An almost equivalent, solution model in which the first sorbed molecules to enter the polymer are accommodated to a large cxtent in existing volumes in the polymer, with successively sorbed molecules swelling the polymer to a greater extent (i.e., partial molal volume of sorbed molecules, TI, increasing with concentration) can also account for these data.
We report Rayleigh ratios at 6937 angstroms for nine organic liquids. The Rayleigh ratios of benzene, carbon tetrachloride, and normal octane are exactly those predicted from published data for ratios at shorter wavelengths and from the inverse fourth power of wavelength dependence of scattering.
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