9—the Effect of the Carboxyl Groups in Viscose Sheet on the Equilibrium Absorption of Chrysophenine G.

The equilibrium absorption of Chrysophenine G on viscose sheet was found to depend on the ratio of the mass of sheet to the volume of the dyebath. This effect, which was greatest when the concentration of sodium chloride in the dyebath was low, was due to the presence in the viscose sheet of acidic carboxyl groups which resulted in a lowering of the dyebath pH. For dyebaths in which the dye concentration and the total cation concentration of the inorganic electrolytes were maintained constant, the equilibrium absorption increased with decreasing dyebath pH and attained a fairly constant value at pHs between 3 and 2. The absorption isotherms of Chrysophenine on viscose sheet were measured under conditions such that the dyebath pHs were about 6. The theory of the effect of carboxyl groups in viscose sheet on the equilibrium absorption is discussed. Tentative calculations based on this theory suggest that the number of carboxyl ions which directly affect the equilibrium absorption may be less than the total number of carboxyl groups in the viscose sheet.