The resonance Rayleigh scattering ( RRS ) intensity of [Ag ( Phen ) 2 ]^+ cation complex formed through the reaction of Ag^+ with 1,10-phenanthroline in phosphate buffer medium could be enhanced significantly when the cation complex further reacted with the acidic triphenylmethane dye (TPMD) including bromophenol blue ( BPB ), bromocresol green ( BCG ) and bromocresol purple (BCP) to form an ion-association complex in the presence of PVA-124. The optimal conditions for the reactions and the spectral characteristics of the complex ...