Metachromatic behaviour of dyes in solvents of high dielectric constant: the anomaly of water

Abstract

The visible absorption spectrum of 1,1′-diethyl-2,2′-carbocyanine bromide has been examined in a variety of solvents of high dielectric constant. Metachromasy is exhibited only in aqueous solutions and to a much smaller extent in glycerol solutions. The results are consistent with the view that the abnormally high tendency of water molecules to self-associate is an important factor responsible for the anomalous metachromasy of dyes in water. The addition of large amounts of sucrose to aqueous solutions of Methylene Blue tends to destroy the metachromasy exhibited by this dye.