In spite of the similarity in chemical properties of gold and silver, the kinetics of the hydrogen-oxygen combination over the two metals show little in common. It appears that no simple mechanism for the reaction in contact with gold is adequate to account for the observed results.The field of photosensitization by mercury vapor has been extended during the past year to processes which do not involve hydrogen. Dickinson and Sherrilll showed that ozone was formed from the collision of excited mercury atoms and oxygen. Since the energy of the quantum corresponding to the 2536.7 A. line is insufficient to decompose an oxygen molecule, they assumed that the reaction occurred through the collision of an excited and normal oxygen molecule.Olson and Meyers12 investigating in more detail the reaction between hydrogen and ethylene reported by Marshall and Taylor, have shown that the reaction does not go smoothly to form ethane. Ethylene itself is polymerized, there being a t the beginning of the reaction an increase in pressure which falls off again as the polymerization proceeds. They also found that the rate of the hydrogen-ethylene reaction was proportional to the square root of the hydrogen concentration.Senftleben3 has found that the excited mercury atoms will decompose water vapor. Measuring the change in heat conductivity of water vapor when mixed with varying amounts of hydrogen and oxygen, he found that the change which occurred when water vapor and mercury were illuminated indicated that hydrogen was the sole product in the vapor phase. He, therefore, postulated the formation of hydrogen peroxide which condensed out.The work here presented has as its object an attempt to broaden the field still further by the development of improvements in light sources for use in photosensitized processes and for general photochemical purposes] and by a study of a number of photosensitized and photochemical reactions. Those investigated are the hydrogenation and polymerization of ethylene and acetylene, the reaction of hydrogen and oxygen to form hydrogen peroxide and the decomposition of water, ammonia, ethylene, ethyl and methyl alcohols, acetone, formic acid, hexane, benzene and

A graph, showing a comparison of results with those of other investigators, is given.The value of the heat of reaction for the dissociation of calcium hydride is found to be 51,100 calories at 1100°K.A brief discussion is given of the mechanism of the reaction.Schenectady, N. Y.

Belowi60°f. (7o°c.) there are in gasoline few naphthenic compounds and no aromatics. Up to this boiling point, gasolines are composed mainly of paraffins with the corresponding olefins. The octane number in this range is primarily dependent upon the relative amounts of the isomeric paraffins present, straight-chain compounds showing a greater tendency to knock than corresponding branched-chain compounds.

According to the Franck-Condon theory for the dissociation of molecules by light, we should also expect that two colliding atoms may recombine with the emission of light. This should occur if conditions are arranged so that there are appreciable quantities of the free atoms present. Experiments were carried out with flames of chlorine and hydrogen and hydrogen-oxygen flames containing the halogens. Spectra of these flames are found to be continuous extending into the ultra-violet. It is shown that the violet limits of these spectra are in agreement with the hypothesis that they are due to the recombination of the normal and excited halogen atoms. Calculations show that there are enough collisions of this type in our flames to account for the intensity of the light emitted.