The solubilities of methyl mercaptan in a variety of aqueous amine solutions have been measured. Mercaptan chemical solubility can be predicted by consideration of acid-base properties of the mercaptan and amine. Chemical equilibrium constants have been used to separate the chemical and physical solubilities from experimental results for 50 wt % methyldiethanolamine. At moderate acid loadings, the chemical solubility is diminished and the physical solubility dominates. This methodology has been extended to aqueous solutions of monoethanolamine, diethanolamine, and diglycolamine.