A literature survey of chemical reactions in or between gases and absorbing solids was performed. A number of suitable reactions were identified and optical, physical, and chemical data were obtained for the solids involved. The optical properties of gas-particle mixtures were studied by developing computer codes to predict their absorption and scattering. A data base was established containing the optical properties for a variety of candidate particle materials. Heat transfer properties of gas-particle mixtures were studied and a model was developed to predict energy flows between particles and gas. A laboratory program was carried out to verify the calculations, measure properties of the gas-particle mixtures, gain experience with radiant receiver systems, and to explore high flux radiant reactions.