The sulfation kinetics of four porous solids with potential as dry sorbents for SO2 in stack gases were investigated using a thermogravimetric method. Supplementary information was obtained by electron beam microprobe analysis, scanning electron microscopy, chemical analyses, surface area measurements and X-ray diffraction. Sulfur dioxide concentrations typical of flue gases and somewhat higher, 0.001 to 0.03 atm, were used. The effect of temperature, sulfur dioxide pressure, oxygen pressure, water vapor and particle size were studied. Alkalized alumina, alunite, manganese nodules, and dry red mud were studied.