UV/Visible spectroscopic studies of the effects of common salt and urea upon reactive dye solutions

The absorption spectra of two reactive dyes were studied by UV/Visible spectrophotometry in the presence of sodium chloride and urea at varying concentrations. Evidence has been produced to show that the effect of adding common salt to a dyebath at neutral pH is to produce increased aggregation of the dye species. In contrast, the addition of urea to a dye liquor results in reduced dye aggregation and the generation of increased amounts of the monomeric species.