The effect of procedural variables-mass and heating and cooling rate-on the maximum capture efficiency Of CO2 is studied, using a carbonation/calcination cycle, for a series of carbonation rocks with different stoichiometries of dolomite and calcite. The extent of carbonation and the cyclability depends particularly on dolomite presence and at the same time seems to be influenced by the existence of impurities. Samples having the highest percentage of calcite and the lowest percentage of impurities seemed to be independent on the above variables. In limestone samples with small quantity of dolomite, impurities or a combination of both of them was observed a very small increase in the extent of carbonation due to the increase in the initial mass of the samples, while these samples in the case of the same initial mass presented an increase in the extent of carbonation due to the decrease in the cooling and the second heating rate. (c) 2004 Elsevier B.V. All rights reserved.