2.2. Instruments
A Cary 1E UVevisible spectrophotometer was employed
for absorbance measurements using quartz cells of path length
1 cm.
A pH meter (Mettler Delta 320, UK) was used to measure
the pH values of the lac dye solutions.
A thermostatted shaker bath (Heto-Holten A/S Denmark,
Type SBD-50 cold), operated at 75 rpm, was used to study
the adsorption isotherm of lac dye onto cotton yarn.