examining the thermodynamics of solids with sorbed water. The compounds studied include nonhygroscopic drugs, a channel hydrate drug, a stoichiometric hydrate excipient, and an amorphous excipient. The water sorption isotherms were measured over a range of temperature to extract the partial molar enthalpy and entropy of sorbed water as well as the same quantities for some of the solids. It was found that water–solid interactions spanned a range of energy and entropy as a function of RH, which was unique to the solid, and which could be valuable in identifying batch-to-batch differences and effects of processing in material performance