A wetted-wall column with molten salt and gas in direct contact passing countercurrent to each other proved successful in controlling the highly exothermic reactions involved in the condensation of acetylene to aromatic hydrocarbon liquids. Numerous salt systems, all of them halides, were investigated over a temperature range of 550°to 625°C. Both pure acetylene and acetylene-ethylene mixtures were studied.Molten systems containing zinc chloride were found to catalyze the reaction as well as toA STUDY of the polymerization of acetylene was undertaken because of a pressing need for benzene in the war effort. The following pertinent conclusions concerning this reaction were reached from a comprehensive survey of the literature.The most suitable reaction temperature lies between 600-700°C ., the slow rate of reaction below 600°C. setting the lower limit, and the spontaneous decomposition of acetylene to carbon and hydrogen with rapid propagation of a flame setting the upper limit. A series of condensation plus hydrogenation reactions takes place between acetylene and hydrogen at temperatures up to 350°C. (5, 6). However, the products are principally of a nonaromatic nature, so that the results obtained in this temperature range are not comparable to those obtained at higher temperatures.The principal reactions involved are of an extremely exothermic nature.3C2H,(g) > C6H6(g) 6 -7 °c-= -148,000 g.-cal. /g.-mole C«H6 3C2H2(g) -*-60 + 3 » AHwo-T»» C. --162,000 g.-cal./3 g.-moles C2H2