THE ACCESSIBILITY OF COTTON TO ANIONIC DYES

Adsorption isotherms have been obtained for two direct dyes on unmerce rised cotton and viscose yarns at the boil in the presence of sodium c hloride. Both dyes, CI Direct Red 81 and CI Direct Green 26, show evid ence of monomolecular layer adsorption. Controlled acid hydrolysis of cotton was carried out in order to remove non-crystalline cellulose, a nd dye sorption values were obtained for the residues. Accessible surf ace areas have been calculated from the saturation values obtained fro m the reciprocal plots of the adsorption data. The results are interpr eted in terms of a crystalline fibril model of the cotton fibre.