THERMODYNAMIC AFFINITY OF ACID DYES ON SILK

The dyeing mechanism of silk with acid dyes is likely to be similar to that of wool and is therefore subject to the same type of uncertainty of interpretation. For wool, two models have been postulated: the model of Gilbert and Rideal, and that of Donnan. In this first approach, for the study of sorption isotherms and for the determination of thermodynamic affinity, we utilized the Gilbert-Rideal model, based on the formulation of a site mechanism. The apparent saturation values S, calculated from the sorption isotherms, showed good agreement with the content of the amino groups of silk fibroin determined experimentally, which supported the proposed site mechanism. A relation was found between thermodynamic affinity values and conjugation in the dye molecules. © 1990.