The influence of sodium chloride on the adsorption of lac
dye on cotton was investigated in a similar manner. The cotton
yarn (0.5 g) was dyed with different dye concentrations
(50 mL) in the presence of 0.5 M sodium chloride at 10 and
30 C. The pH of the dye solution before and after dyeing
was measured in each experiment. The absorbance of the
dye solution was measured at lmax 487 nm.