The aggregation of the tetrasodium salt of copper phthalocyanine 4,4',4',4''-tetrasulphonic acid

Abstract

The aggregation of the tetrasodium salt of copper phthalocyanine-4,4',4",4??? tetrasulphonic acid has been investigated by equilibrium spectrophotometric measurements at 25º. At low concentrations this can be treated in terms of a monomer-dimer equilibrium. Owing to the strong aggregating tendency of this molecule in water, it was necessary to evaluate the dissociation constant together with the monomer and dimer spectra from measurements made in 20% ethanol solutions. By means of these data, the corresponding dissociation constant in water has been determined.