The Thermodynamics of Sorption of Three Direct-Dye Mixtures on Cellulose

The equilibrium absorption of binary mixtures of Direct Red 2, Direct Blue 8, and Direct Yellow 12 by cellulose film has been studied, and a correlation between single and mixture dyeing is presented.In each case, the competition of the dyes for available surface area suppressed the sorption. In some cases, evidence was obtained of interaction of the dyes in solution. When this occurred, it was difficult to define quantitatively the com petition of the dyes for available surface area. All of the results correlated with the degree of interaction in solution, as measured by transmission studies made at 90°C.The data are interpreted in terms of a Langmuir equation which has been modified to take into consideration the compe tition of two dyes for available surface area.