Novel, 1,4-bis-[3,3'-phenyl-5,5'-(o-carboxyphenyl)-formaz-1-yl]-benzene-o-sulphonic acid and its derivatives contained -OH group at the o-, m-, p-positions of the 3-phenyl ring were synthesized. The structures of the formazans were confirmed by elemental analyses, GC-mass, IR, H-1 NMR, UV-vis spectra. Their absorption properties were investigated. It was seen that lambda(max), values shifted towards shorter wave lengths by 130 nm in CSPF relative to 1,3,5-triphenylformazan (TPF) due to the fact that the structure of CSPF contained electron withdrawing -COOH and -SO3H groups (hypsochromic effect). With binding of -OH group to 3-phenyl ring of CSPF, it was observed a small bathochromic effect in accordance to the electron donating effect of -OH group. (C) 2007 Elsevier B.V. All rights reserved.