The Effect of Buffer Systems on the Uptake of Acid Dyes by Wool and Nylon

For the measurement of adsorption of acid dyes by wool and nylon a dyebath pH of 4 can be achieved either by the use of aqueous solutions of acids, e.g. formic acetic or sulphuric acid or by the use of standard buffer solutions, e.g. acetic acid/sodium or ammonium acetate, phenylacetic acid/potassium phenylacetate or potassium hydrogen phthalate. In this work, wool yarn and nylon 6 filament have been dyed from aqueous solutions of C.I. Acid Reds 1 and 41 at a pH value of approximately 4.2 in the presence of either aqueous acetic acid or a selected pH 4 buffer. The effect of each buffer system on the rate of adsorption of each dye by wool and nylon fibres has thus been studied. It was found that, in some cases, the buffer system had a significant effect on the rate and extent of dye uptake. The use of potassium hydrogen phthalate, a primary pH standard, to produce a dyebath pH of 4.2 gave a greatly reduced adsorption of the two dyes by both fibres