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

Abstract

The effect of urea and thiourea on the aggregation of copper phthalocyanine-4,4?,4?,4??-tetrasulphonic acid in aqueous solution has been studied using the capillary diffusion technique. The addition of excess inert electrolyte was necessary in order that the measurements were not complicated by facilitated diffusion. The extent of aggre- gation has been estimated empirically from the dependence of the diffusion coefficient on molecular weight. The significance of both the changes in diffusion coefficient and the dissociation of the dye, in relation to dyeing behaviour, is discussed.