MULTIFUNCTIONAI, IONIZAT ION AS ILLUSTRATED BY THE CLAY MINERALS 1 By

The electrochemical propertie_ ~ of clays are discussed under four rules which arise from considerations of file bonding energy of ions associated with charged surfaces. The mean free bonding energy of a cation associated with a negatively charged surface is determined by calculation from conventional potentiometric measurements with membrane lectrodes. The first three rules are concerned with ttle effects of valency upon ionization. They arise directly from the melhod of calculating cationic mean free bonding energies, applicable to monofunctional surfaces as regards Rule 3, and to polyfuncfional surfaces also as regards Rules 1 and 2. The fourth rule (Jarusov's rule) deals ~-i~tl mixtures of cations on polyfunelional surfaces. It may be expressed verbally by stating that the cation wilh the higher mean free bonding energy preempts those positions on the surface which manifest greater mean free bonding energy. The incidence of each rule is examined, using data from studies of cationic activities in clay systems. The factors which cause deviations from these idealized rules are discussed. Graphical data are presented for Wyoming bentonite, Arizona bentonite (montmorillonite), and Putnam clay (montmorillonite group); illite, kao-linite and attapulgite