Abstract: The properties of silica gels sensitized by methyl orange and its homologues were critically examined in order to decide between the alternative hypotheses of a lock and key mechanism and an association mechanism to explain the enhancement of adsorption. Evidence appears to favor an association mechanism in which the unextractable dye particles act as centers to attract their own kind more strongly than one of their homologues. Nitrogen area measurements show that less than 0.5% of the gel surface area is used in adsorbing dye molecules. The dye series from methyl to butyl orange have a very sharp increase in solubility from ethyl to propyl when dissolved in 5% aqueous acetic acid solution (pH = 2.3).
Template and target information: methyl orange, ethyl orange, propyl orange, butyl orange