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 spec trophotometry in the presence of sodium chloride and urea at varying concen trations. Evidence has been produced to show that the effect of adding comm on salt to a dyebath at neutral pH is to produce increased aggregation of t he dye species. In contrast, the addition of urea to a dye liquor results i n reduced dye aggregation and the generation of increased amounts of the mo nomeric species. (C) 1999 Elsevier Science Ltd. All rights reserved.