This work has so far been concerned mainly with montmonllonite. We have been attempting to study the behaviour of this mineral in contact with different reagents. It was with this general idea that Miss R. Glaeser took up the study of equilibria in the vapour phase with a series of organic substances. The first results are expected soon. The principal difficulty arises from the fact that it is necessary to operate in an anhydrous medium: as is well known it is difficult to eliminate all the water fixed by montmorillonite without partially altering the mineral.