In previous studies micronized disodium fluorescein (DF) powders were coated with lauric or capric acid. This was a precursor to evaluating the effects of the fatty acids on the hygroscopic growth of the DF aerosols. Studies of the association of fatty acids with DF reflected a limited interpretation of the data obtained. The present study examines more closely the phenomena involved in coating the DF. It is concluded that lateral interactions due to the hydrophobic aliphatic tails of the fatty acids give rise to adsorption, aggregation, and flocculation, all of which cause inflections in the association isotherm rendering it nonlinear. (C) 2003 Wiley-Liss, Inc
