This paper deals with the volumetric absorption of solar radiation in particle-gas suspensions. The optical properties of different carbonaceous particles in connection with solar radiation on the basis of Mie＇s scattering theory are discussed. An efficiency factor for reflection was introduced to determine the solar radiation scattered backwards in a hemispherical angle towards the source of radiation. Projections of the relevant optical properties of individual small particles of black and brown coal, anthracite, carbon black and coke are illustrated and compared. Extinction experiments were performed and are presented, and experimental and theoretical results are compared. Some practical experiences of particle production and particle-gas suspension characteristics are presented. The results of experiments and analysis show which substances and particle sizes are most appropriate for the absorption of solar radiation in particle-gas suspensions.