At pH > 2.5, however, the ionic interaction between the
carboxylate anion of the dye and cationised cotton fibres decreases
due to the decreasing number of protonated terminal
amino groups of cationised cotton fibres and thus lowering
its dyeability. It is to be mentioned that the lower dyeability
in the case of US method than in the case of CH method at
pH > 2.5 may be attributed to the enhanced desorption of
the dye as its ionic bond is getting decreased.