Gas chromatography was used to identify and to determine volatile products from the Homogeneous Reactor Test and from the processing of nuclear fuels and wastes. A gas Chromatograph was constructed and used for part of the separations. It differs from conventional chromatographs in having an all-Pyrex gas-sampling system and all-Pyrex columns for use in the analysis of corrosive gases, that is, the oxides and chlorides of nitrogen. Temperature programming of the molecular-sieves column was used to advantage in the determination of the oxides of nitrogen and of carbon. The effect of the adsorption characteristics of type 5-A molecular sieves with respect to the adsorption-desorption of water and of nitric oxide was determined; both effects are significant in the analysis of mixtures of the oxides of nitrogen. The versatility of molecular sieves as an adsorbent in gas-solid chromatography was exploited in this work.