This work has so far been concerned mainly with montmonllonite. We have beenattempting to study the behaviour of this mineral in contact with differentreagents. It was with this general idea that Miss R. Glaeser took up thestudy of equilibria in the vapour phase with a series of organic substances.The first results are expected soon. The principal difficulty arises fromthe fact that it is necessary to operate in an anhydrous medium: as is wellknown it is difficult to eliminate all the water fixed by montmorillonitewithout partially altering the mineral.