Basal spacings of a Ca-montmorillonite equilibrated in aqueous solutions of methanol, ethanol, n-propanol, 1,2-ethanediol, 1,5-pentanediol, acetone, dioxane and morpholine, are measured at concentrations ranging from 0-100 mole percent organic component. With solutions of the monohydric and dihydric alcohols, the basal spacings increase with increasing mole fraction of the organic component up to a limit beyond which the spacing diminishes rapidly almost to that given by the pure organic material. The expansion limit occurs at the following mole fractions of organic material: methanol 47%, ethanol 35%, propanol 8%, ethanediol 7%, propanediol 8%. Acetone gives complete dispersion of Ca-montmorillonite in the range 0-10 mole percent, expansion to 26.5 Å in the range 20-60 mole percent, expansion to 22 Å in the range 80-90 mole percent. Dioxane and morpholine give constant spacings over the entire range from 1-100 mole percent. The significance of these results is discussed.