2.1. Bifunctional reactive dyes
The first commercial reactive dyes for cotton were based on the dichloro-s-triazine reactive group. Since then many other reactive groups have been developed(Ahmed, 1995). The most widely used reactive groups, in the order of increasing level of reactivity, are trichloropyrimidine, aminochloro-s-triazine sulphatoethylsul phone, dichloroquinoxaline, aminofluoro-s-triazine, difluoro- chloropyrimide and dichlorotriazin. The extent of dye-fibre reaction and the ultimate discharge ofunfixed dye vary widely with the type of reactive group and the dyeing technology used.