Solubility of 2,6-diphenyl-4-(2,4,6-triphenylpyridinium-l-yl) phenolate, commonly known as Reichardt' s betaine dye and a ketocyanine dye has been determined in binary solvent mixtures and in cationic and anionic micellar media. In all the binary mixtures the standard molar free energy of solution, as given by log Sl2 where 512 is the solubility in the binary mixture, cannot be represented by t...