The solubility of carbon dioxide in ionic liquids was measured in a new apparatus. The ionic liquids chosen have ammonium-based cations and show melting temperature decreases under CO2 pressure that range from low (25 K) to extremely high (120 K). The main purpose of this study was to check whether the solubility of the gas in each liquid could explain the previously reported wide differences in melting point depression (MPD). The results show there is no correlation between solubility and MPD. (C) 2013 Elsevier B.V. All rights reserved.