RELATION OF COLLOIDAL HYDROUS OXIDES TO THE HIGH CATION-EXCHANGE CAPACITY OF SOME TROPICAL SOILS OF THE COOK ISLANDS

Abstract

Cation exchange capacity of some soils, Lower Cook Is., is due mainly to amorphous colloidal hydrous oxides. Artificially prepd. amorphous hydrous oxides Al and Ti had very high exchange capacities, those of Fe and Si less. All had distinctive thermal curves. Curves of soils, clays, and hydrous Al oxides had multiple endothermic peaks between 100[degree] and 600[degree]C, which differed from those of Fe, Ti, and Si, suggesting that amorphous hydrous Al oxides are the principal exchange materials.