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A simple apparatus has been developed for fractionating polycomponent gas samples at temperatures at which the take-off pressure is of the order of 0.5 mm. Fractions as small as 0.06 cc. of gas have been isolated and their vapor pressures determined.

The homogeneous gas-phase reaction H+p-H2=o-H2+H has been studied in the temperature range 300° to 444°K. Within this range the results fitted the equation log10k1 = 15.454 − 3.490×103/T+3.836×105/T2 cm3 mole−1 sec−1. The results were interpreted in terms of activated-complex theory with quantum-mechanical tunneling. From the information about the tunneling factors provided by the curvature of the Arrhenius plot it was possible to calculate the imaginary frequency of the asymmetric vibration of the complex corresponding to its coordinate of decomposition on the assumption of a truncated parabolic barrier. The value obtained was 1213i cm−1. For the same model ΔE0° was found to be 9.7 kcal mole−1. The almost exponential dependence of the tunneling factor on 1/T for Eckart barriers made it impossible to interpret the curvature in terms of such a barrier except for considerably larger values of barrier height and/or imaginary frequency than have been found in recent theoretical calculations.

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