Some experiments were accomplished on the absorption of hydrogen atoms by palladium, and palladium-gold alloys. This work was carried out in connection with some earlier work on the catalytic effect of these metals and alloys on the recombination of hydrogen atoms. The attack of a number of metals by molecular and atomic oxygen was examined in order to discover in which cases there were considerable differences in rate. Experiments were also undertaken on the recombination of oxygen atoms on the surface of the alkali metal tungsten bronzes. A pressure gauge is described which was devised for the rapid and convenient measurement of pressures in mixtures containing chlorine at pressures of the order of 1 mm., the accuracy being about =0.01 mm.