The ionization constants of some substituted 5-(phenylazo)-8-hydroxyqu
inolines were determined potentiometrically in aqueous solutions conta
ining different percentages of ethanol, acetone and isopropanol. The r
esults were discussed in terms of solute-solvent interaction and the i
nfluence of dielectric constants. The ionization constants in pure aqu
eous media were evaluated and the coplanarity of the above derivatives
was discussed.