The adsorption of beta-carotene I. by bleaching earths

Activities of various bleaching earths for removal of β‐carotene from acetone solution were found to be in the decreasing order tonsil, fuller's earth, silica, and kaolin. Experimental evidence indicated that except for silica, in addition to physical adsorption, processes involving chemisorption and subsequent chemical reaction proceeded on the surface of the clay minerals. An Arrhenius activation energy of the order of 10 kcal mol−1 was found for the adsorption of β‐carotene from a solution in acetone on tonsil. Metallic ions, such as Fe3+, are suggested to be the active sites for chemisorption and reaction. Oxygen was not essential for activity.