Free energy of hydration calculations for butane and octane were conducted at several state points. A relatively new method of performing the alkane insertion was used and it was found to perform quite well. Our preliminary simulation results are in good agreement with the recent equation of state (EOS) predictions of Yezdimer et al. [Chem. Geol. 164 (2000) 259] and suggest that at near-critical conditions the isobaric solubility curves for a series of alkane chain molecules may unexpectedly reverse.