Chemical reaction between CO2 and Li4SiO4 was investigated using thermogravimetry under various P(CO2). Under P(CO2) of 1.0 bar, weight increase originating from CO2 absorption reaction was observed from similar to 500 degrees C and abrupt weight reduction due to CO2 desorption was detected at similar to 700 degrees C. With decreasing P(CO2), the latter temperature decreased. Since fair agreement was observed between the latter temperatures and thermodynamically calculated equilibrium temperatures of Li4SiO4 + CO2 <-> Li2CO3+Li2SiO3, the latter temperatures could be regarded as approximate equilibrium. Dependence of the calculated equilibrium temperatures and approximate equilibrium temperatures on P(CO2) was represented with Ellingham diagram, showing P(CO2) and temperature region of CO2 absorption or desorption. Approximate equilibrium temperatute under P(CO2) of 1.0 bar agreed with the calculation, whereas deviation was observed under low P(CO2), resulted in larger apparent AS and All than the calculated ones. Using specimen with smaller particle size, the deviation reduced clue to enhancement of CO2 desorption kinetics. (C) 2017 Elsevier Ltd. All rights reserved.