Dodecylammonium-Mica Complexes—I Factors Affecting the Exchange Reaction

E. E. Mackintosh*, D. G. Lewis and D. J. Greenland
Waite Agricultural Research Institute, University of Adelaide, Glen Osmond, South Australia 5064
* Present address. Department of Soil Science, University of Guelph, Guelph, Ontario, Canada.

Abstract: Dodecylammonium chloride (DAC) is used as a reagent to displace potassium from a wide range of mica minerals. Displacement is rapid and essentially complete for trioctahedral micas even in dilute solutions (0·02N DAC) at low suspension concentrations. Increasing the suspension concentration, or the concentration of potassium in the extracting solution decreased the extent to which potassium could be displaced before equilibrium was established. Under standardized conditions of temperature and suspension concentration, the rate of potassium displacement increased as the particle size decreased although complete displacement was more difficult to achieve for the finest fraction (< 2µ) than for the coarser particles.

The trioctahedral samples were shown to be more susceptible to potassium depletion by DAC than dioctahedral material. Within the range of trioctahedral samples examined the rate of reaction was found to be closely related to the fluorine content of the sample. Data obtained for the more resistant dioctahedral specimens was not sufficiently detailed to enable any similar relation to be established.

Clays and Clay Minerals; September 1971 v. 19; no. 4; p. 209-218; DOI: 10.1346/CCMN.1971.0190402
© 1971, The Clay Minerals Society
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