Swelling of Montmorillonite in Polar Organic Liquids

-The crystalline and osmotic swelling of N~, Cs-, Mgand Ca-montmorillonite has been measured in dimethyl sulphoxide and in formamide, N-methyl formamide, dimethyl formamide, N-methyl acetamide and dimethyl acetamide. These liquids have similar dipole moments but their relative permittivities vary appreciably from values less than water to values greater than water. Na montmorillonite exhibits osmotic swelling (diffuse double layer development -d(001) ~ 19 A) in formamide and N-methyl formamide and Cs gives osmotic swelling behavior in formamide. Cs-montmorillonite in the crystalline swelling region give spacings greater than those found for water with all liquids. Mgand Ca-montmorillonite did not give spacings greater than 19 A in any of the liquids studied. The swelling behavior of montmorillonite is affected by relative permittivity but for liquids with a similar relative permittivity methyl substitution in the molecule may prevent the development of diffuse double layers on the particle surfaces.