NOTE

2H NMR quadrupolar splittings of clay suspensions monitor the orientation of water molecules near the solid surface. Two limiting water interfacial sites explain our results on montmorillonite, hectorite, and saponite suspensions. The location of cation isomorphous substitution and the Ca2+/Na+ molar ratio of exchangeable cations modulate their relative importance. With beidellite suspensions, water orientation at the clay surface cannot be described within the above scheme.