Deformations of cation-substituted vermiculite (Na, Ca, and Ba forms) upon water vapor sorption have been studied. To solve this problem a dilatometer was used. Its main part was a line differential transformer, the core of which was connected to the sorbent by means of a rod. Any changes of the sorbent height caused a change in the core position in the transformer, which influenced the signal recorded from its secondary winding. The sorbents used were plate-formed, anisotropic, and swelled only in the direction perpendicular to the plane of the plates. The results obtained were compared with the adsorption, calorimetry (a Calvet-type microcalorimeter with a microbalance attachment was used) and X-ray data. High sensitivity of the dilatometric method to the structural changes of the laminated silicates whose cell structures expand upon hydration has been shown. (C) 1994 Academic Press, Inc.