In the context of the reduction of the greenhouse gases emissions, the CO2 geological storage in aquifers seems inevitable today. The gas mixture, which is captured in the industrial effluents, contains CO2 and a small quantity of annex gases such as SO2, NO or O2. It is fundamental then to understand the role of those gases on the geological behavior of the aquifers to ensure safety of the storage. This project is conducted order the hospice and the financial support of the French National Agency for Research (ANR SIGARRR). The main thrust of this project is to conduct geochemical and thermodynamic simulations to model the long-term behavior of co-injected gases within CO2 storage sites. Our main goal in this global project is to understand the thermodynamic behavior of gases (CO2, SO2, NO and O2) in aqueous salted solutions representative of the aquifers. We will determine experimentaly the enthalpies of solution and solubilities of gases in the aqueous solutions as function of the temperature, the pressure and the nature of the salts using calorimetric technic. The results will be used to validate and improve the equations of state developed by the other partners of the SIGARRR project. The calorimetric technique used in this work is similar to the one used previously to study the dissolution of CO2 in aqueous solutions of amines or for the dissolution ofCO2 and H2S in sodium chloride solutions. The heat of mixing of CO2 in aqueous solutions are measured using a custom-made flow-mixing cell adapted to a Setaram C-80 heat conduction differential calorimeter. This unit was housed in the calorimetric block, where the heat effect during the absorption of the gas into the aqueous solution of amine was detected by thermopiles. Enthalpies of solution of CO2 (solH) are then obtained as function of loading charge  (moles CO2 / mole solvant) for a constant temperature and pressure. Solubility values of the gas into the solutions (s) were derived from the enthalpic data. This poster will present the experimental technique used together with the calibration procedure and the uncertainty determination. Then, first results obtained for mixing of carbon dioxide in water and in aqueous solutions of calcium chloride will be detailled.