Part III.—Manufacturing processes. On the theory of the dyeing process. The influence of acid-dyes on animal fibres

Kinetics of Wool Dyeing with Acid Dyes

“…At constant pH, there is a decrease in the amount of dye taken up by the wool as the concentration of the acid anion increases (Table II). These data, taken with the pH increase during dye uptake, are consistent with the hypothesis that the acid anion and the dye anion are involved in competing equilibria, rather than the strict one-for-one displacement of the acid anion as proposed by E16d [4]. Release of some of the acid anion will occur during dye uptake, but it will be due to the shift in the acid anion-site equilibrium as the number of unoccupied sites decreases with the uptake of dye.…”

“…Gilbert and Rideal [5] proposed that dye uptake is an anion exchange process, in which the dye molecules displace smaller anions. Evidence for this ion exchange concept appears to rely on one study [4], the results of which have been contradicted [ 11 ].…”

The Sorption of Soluble Dyes by Gelatin.

“…Experiments with Tartrazine (a) with a high concentration of external dye solution (at 25°C.) over a short period, and (6) with a low concentration (at 15°C.) over periods up to 48 hr., indicated that the dye sorption proceeds as a diffusion process.…”

“…Elod and his collaborators (6) have given evidence that in an (acid) dye bath containing both mineral acid and dye, equilibrium between a protein and the acid is established much more rapidly than between the dye and the protein, the dye anion then displacing the inorganic anion from the protein. This is consequent on the higher mobility of such an anion as Cl-(molecular weight, 35.5) over a dye anion of, say, ten to twenty times its magnitude.…”

“…No survey will be given of the rather scattered literature upon this subject. A useful, if not complete, bibliography is given in the paper by E. Elod (6), which covers the subject up to 1932. Specific references will be noted where pertinent.…”