INTERLAYER FORCES IN BENTONITE 1 By

An attempt is being made to analyze the forces between unit layers of a bentonite particle and between the flat surfaces of two particles from colloid chemical data and theory. The electric doub!e-layer interaction, the van der Waals attraction, and the hydration energies are considered. From experimental observations the general qualitative shape of the net potential curve of interaction may be derived. In a quantitative discussion, first the long-range interaction is considered by applying the theory of Verwey and Overbeek in which the net interaction curve is found as the sum of the double-layer repulsion and van der Waals attraction. The fact that the layers do not spontaneously dissociate in solution despite the high charge density of the surfaces points to a considerable specific adsorption potential of the counter ions (the exchangeable ions) to tile surface (~0.2 ev). The consequences for ion exchange are briefly discussed. Next, two possibilities for the status and position of the counter ions are con