The sulphation properties of activated soda samples obtained by the thermal decomposition of natural trona samples were studied. The effect of thermal decomposition temperature on the physical properties and the total sulphation capacity of activated soda samples was investigated. Sulphation reactions were conducted at two different temperatures of 423 K and 473 K in a gaseous mixture consisting of 10% CO2, 5% O-2 and 0-5% SO2 and a balance of nitrogene by volume with a constant flow rate of 355 cc/min. It was found that the physical properties of activated soda samples were strongly effected by the thermal decomposition temperature. Measured sulphation capacities and conversion values of activated soda samples were found vary depending on their physical properties and changed between 152.07-187.77 mg SO2/g activated soda and 80.60-99.52%, respectively.