REACTION BETWEEN CESIUM AND CARBON BLACKS

A series of composition vs. pressure isotherms have been determined for the reaction between cesium and two carbon blacks in the temperature range from 350° to 550°C. A graphitized and a normal carbon black were equilibrated with cesium vapour at pressures from 4·5 to 5000 μ. The cesium content of the carbon black sample was measured by means of a radioactive tracer technique. Hysteresis was found to exist in the isotherm data. The data show evidence of a diffuse two phase region corresponding to the region 5 7C24Cs(s) + Cs(g) ⇌ 12 7 C10CS(s) previously shown to exist in the cesium-graphite system. An explanation is offered for the hysteresis observed in the cesium-carbon black and cesium-graphite systems in terms of the structural rearrangement of the graphite layers required by the phase change. Heats and entropies of reaction are calculated from the data and these are compared to the values observed in the cesium-graphite system. © 1968.