The models are initially compared against the experimental data from Stoessel and Byrne . In these experiments, the authors measured the solubility of methane at 25⁰C at moderate pressures (24-51 bar) in aqueous solutions containing different salts (e.g., NaCl, CaCl2, Na2CO3). The amount of gas dissolved was calculated from the total gas volume and pressure change in the gas phase upon equilibration with the aqueous phase by using the ideal gas law. Figure shows the performance of PHREEQC and Reaktoro for predicting the solubility of methane in NaCl (panel a), KCl (panel b), CaCl2 (panel c), MgCl2 (panel d), Na2CO3 (panel e), K2CO3 (panel f), MgSO4 (panel g) using both pitzer and phreeqc databases. The results obtained with the two software programs are primarily identical when the same database is applied. Discrepancies between PHREEQC and Reaktoro were only observed when using phreeqc.dat for describing the methane solubility in MgSO4 and Na2CO3 aqueous solutions. Moreover, with the pitzer database, the solubility of methane in electrolyte solutions of increasing ionic strength was not predicted correctly by neither PHREEQC nor Reaktoro. The models are also compared against experimental data obtained at higher temperatures and pressures. O'Sullivan and Smith measured the solubility of methane in water and NaCl solutions (1 and 4 molal) up to 125⁰C and 600 atm. Figure shows the predictions of the Reaktoro and PHREEQC models against the experimental measurements obtained at a fixed temperature and increasing pressures (panels a to c) and at a fixed pressure and increasing temperatures (panel d). Using the phreeqc database, both Reaktoro and PHREEQC satisfactorily predict the solubility of methane.