A series of four new azo dyes have been synthesized by coupling 
2,4-dihydroxybenzoic acid with m-nitroanline (I), p- aminobenzoic acid
(II), p-aminophenol (III) and p-toludine(IV). The chemical structure of the
newly prepared azo compounds was characterized by elemental analysis, 
IR and 1H-NMR spectra. The electronic absorption spectra had been 
investigated in ethanol and organic solvents of varying polarities. The
important IR bands,
1
H-NMR signals and absorption bands in the UVvisible region were assigned and discussed in relation to molecular
structure. The absorption spectra of the azo compounds were studied in
buffer solution of varying pH values containing 30% (v/v) ethanol from
which the corresponding pKH values were determined.