This is shown by the decrease in the max of both the monomeric and, to a lesser extent, the soluble aggregate species of the dyes. Urea has the converse to salt, in that it increases the concentration of monomeric species in solution. This is evidenced by the increase in the max of the monomeric species relative to that of the soluble aggregate species. This technique may be used to assess the salt/urea sensitivity of reactive dyes and thereby help to dene conditions for their eapplication to cellulose.