The reaction between K and HBr has been studied by a molecular beam technique, using as a detector a surface ionization gauge with a tungsten and a platinum alloy filament, the former sensitive to KBr as well as to K and the latter essentially to K only. The activation energy is 3.4±0.1 kcal/mole and the probability or steric factor is about 0.1. The angular distribution of the KBr suggests that collisions with the H end of the HBr are more often fruitful than other configurations. The total collision cross section for a beam of K at 504°K in HBr at 401°K is 850×10—16 cm2.

The ionization of all of the alkali metals on tungsten and on tungsten oxide surfaces follows the Saha-Langmuir equation with no reflection. On platinum, however, a departure from this equation indicates partial reflection of the atoms. The reflection of Na is probably 0%, since the ionization efficiency is given closely by the Saha-Langmuir equation with a value of 5.50 ev for the work function of Pt at 2000°K. The same value of the work function then indicates reflections of 18% for Li, 48% for K, 22% for Rb, and 8% for Cs, at 2000°K.

Free radicals produced in various substances by C060 gamma rays have been observed by the paramagnetic resonance method. A sufficient concentration has been obtained by performing the irradiation and observation at liquid nitrogen temperature, where the radicals are stably trapped. One pair of lines observed in irradiated HzSO4, HC1O4 and H3P04 has been identified as arising from atomic hydrogen as shown by deuterium substitution experiments and a consideration of the strength of the hypexfine interaction. Atomic hydrogen is also formed from water adsorbed on glass surfaces. Atomic hydrogen was not found in irradiated ice. The presence of additional, weak paramagnetic resonance lines gives information on the environment of the atomic hydrogen, while warming experiments give rate data that indicate second order kinetics for the disappearance of atomic hydrogen.

Specimens of ultra high strength steel were charged cathodically with hydrogen or immersed without charging in a normalNaOH solution of NaC14N and the adsorption of C14N groups determined by means of radioactivity measurements. In addition, the desorption of adsorbed C14N groups was also studied. Heats, designated heats of adsorption, energies of activation, and the surface coverage with C14N were calculated. Hydrogen embrittlement by measurement of bend ductility, negative overvoltage, and the relative hydrogen coverage were determined under similar conditions and with similar materials. It is concluded that C14N groups are strongly and preferentially adsorbed on highly active centers and the hydrogen recombination reaction retarded accordingly. The rapid increase in hydrogen embrittlement with increasing surface coverage by C14N is ascribed to a high surface concentration of the embrittling hydrogen atoms, followed by rapid migration into the steel.

Molecular association equilibria in alkali halide vapors were studied by measuring the temperature dependence of the molecular weights of gaseous NaCl, NaBr, NaI, KCl, KI, RbCl, and CsCl. The molecular weights were determined by measurement of the absolute pressure exerted by a known weight of completely vaporized salt contained in an isothermal fused silica bulb of known volume. The pressure sensing element was a fused silica manometer containing molten gold. The apparatus was used in the temperature range of 1175° to 1430°K and pressures of from 10 to 40 mm were measured with a precision of ±0.05 mm. The temperature dependence of the equilibrium constants for the reaction (MX)2⇌2MX yielded dissociation energies (evaluated at 1300°K) ranging from 48.0 kcal mole−1 for NaCl to 34.7 for CsCl. The entropies of dissociation were found to fall within a small range, varying from 28.3 eu for NaCl to 25.0 for KI, and a statistical calculation of the entropy changes based on an ionic model was found to agree well with the experimental values. It is shown that these systems may be adequately described with an electrostatic model, although closer attention should be paid to the nature of polarization interactions.