Differential Thermal Analyses of Clays Treated With Organic Cations as an Aid in the Study of Soil Colloids

WHEN the colloidal material in the upland soils of the western part of the Corn Belt is examined by the common techniques of clay mineralogy, a general similarity in mineralogical makeup is evident. Clays of the montmorillonite and illite groups are the dominant inorganic exchange materials. In view of the study by Ross and Hendricks (10)' of the montmorillonite group of clays, it seems likely that important variations may occur among the montmorillonite clays found in soils. A method which would indicate differences within this group of clays might furnish information which would help in interpreting soil properties. One possibility for obtaining information of this type was suggested by Cornet (3). In his work the ammonium ions held in interlattice positions could apparently be separated from those held on edges and outer surfaces of the montmorillonite clay particles. This separation was made possible by a stepwise volatilization of the adsorbed ammonia when ammonium saturated clays were heated. The experiments reported here were initiated to determine whether or not other volatile cations such as amines or other nitrogen bases were volatilized from the exchange complex upon heating in a manner similar to that found by Cornet for ammonia. It seemed probable that the energy changes incident to volatilization of these ions might be of sufficient magnitude to permit the reaction to be followed by the procedures commonly used in the differential thermal analysis of clays.