The effect of sodium chloride, and pretreatment of cotton
with chitosan, on the adsorption of lac dye was also studied.
An increase in the sodium chloride concentration over the
range 4.31!103e6.84!101 M led to an increase in the
dye adsorbed onto the cotton and this remained constant in
the concentration range 10.3!101e17.1!101 M when
cotton fibres were dyed with lac dye solution without pH
control. It is believed that the sodium ion (NaC) can distribute
between the external solution and internal solution so that the
negative charge on the cellulose surface is neutralized or
shielded, allowing the lac dye molecules to be adsorbed onto
the cotton [3,16,17].