1—the Absorption of Chrysophenine G by Cotton and by Acidic Oxycelluloses

The equilibrium absorption of Chrysophenine G by cotton cellulose, and by acidic (carboxyl containing) oxycelluloses prepared from it, has been investigated. The introduction of carboxyl groups into the cotton cellulose by oxidation results in a lowering of the absorption of the dye from solutions at pH 7, but not from solutions at pH 3, the effect being greater at low, than at high, salt concentration. When the pH and the salt concentration are kept constant, the isotherms relating the absorption to the concentration of dye in the solution fit the Freundlich equation; the exponent n does not increase significantly with increasing carboxyl content of the cellulose material. For cotton the relation between the salt-dye ratio and the substantivity ratio is almost independent of the dyebath composition over a limited range of salt concentration; there are, however, small deviations from a unique relation. For the acidic oxycelluloses the substantivity ratio at a constant salt-dye ratio decreases considerably with decreasing salt concentration—an effect predicted by theory. Supplementary measurements with viscose sheet, which may be regarded as a regenerated acidic oxycellulose, show that the relation between salt-dye ratio and substantivity ratio depends partly on the degree of swelling of the sheet. The significance of these results is discussed.