Adsorption of β‐carotene: II. On cation exchanged bleaching clays

X‐ray diffraction patterns of a number of commercial bleaching earths indicate that they consist mainly of montmorillonite mixed with smaller amount of kaolinites as well as mica, quartz and cristobalite. The active sites in these earths for the adsorption of β‐carotene are identified through ion exchange and found to be the protonic sites and some metallic ions. The efficiencies of the various cations in imparting activities to the earths are found to be in the order Mg 2+ > Fe 3+ > H + > Ca 2+ > Na + . For Fe 3+ and H + exchanged clays, the activity was found to be linear function of the concentration of these ions. The high activities of Mg 2+ and Ca 2+ exchanged clays are discussed.