Studies of the Aggregation of Dyes. A Spectrophotometric Method of Determining the Aggregation Numbers of Dyes

Abstract

Abstract The aggregation of dyes in an aqueous or alcoholic solution has been studied spectroscopically by a method named the “maximum slope method.” The method can ascertain the molar absorptivity and formation constant of dye aggregate when a simple equilibrium model between a monomer and an n-mer is assumed to be operative, and when the absorptivity of monomer is given. Further, the molar absorptivities of the monomer and the polymers and the formation constants of the polymers are adjusted, in order to minimize the mean deviation, by an other method, named the “minimum deviation method.” Using the latter method, the parameters of an equilibrium system including a monomer and several polymers can also be calculated. Aggregations of Benzopurprine 4 B and Sky Blue FF in aqueous salt solutions were studied by the above two methods. Aggregations of these dyes in aqueous alcoholic solutions were also discussed.