The HP-8451 spectrophotometer was used to record the decay and regular periodic oscillation reaction in 12 aqueous solution systems which include 3 triphenylmethane dyes and 9 bisazo derivative of chromotropic acids. The optimal conditions for the reactions included; absence of stirring, certain concentration range, and ~25? The oscillations, appear >1000 s after the irradiation start. The main oscillating period is 112 ?5 s and the large amplitude is 0.06 A. The effects of concentration, temperature, and stirring on forming photochem. reaction oscillations, were studied and their possible mechanisms are discussed.

Key words: PHOTOCHEMICAL REACTION, TEMPERATURE, CONCENTRATION, CHEMICAL OSCILLATIONS, AZO COMPOUNDS, TRIPHENYLMETHANE P, CHROMOTROPIC ACID