Acta Phys. -Chim. Sin. ›› 2002, Vol. 18 ›› Issue (11): 979-984.doi: 10.3866/PKU.WHXB20021104

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Soap Liquid Membrane Oscillators

He Zhan-Bo;Li Dong-Mei;Shi Yu-Quan   

  1. Department of Chemistry, School of Science, Tianjin University, Tianjin 300072
  • Received:2002-01-25 Revised:2002-04-20 Published:2002-11-15
  • Contact: He Zhan-Bo

Abstract: A new liquid membrane oscillator has been discovered experimentally, in the reaction of producing soap between the two phases of oil and water, pH oscillations appeared near the interface lasting a long time with large amplitude. When the system of W/O two phases was changed by three phases of W1/O/W2, the amplitude changed from pH 0.50 to pH 2.88. The constitution of the liquid membrane oscillator is two aqueous solutions of CTAB and NaOH, respectively and an oil phase of kerosene solution of oleic acid. In addition, obvious oscillations of electric potential and conductivity have also been discovered in the liquid membrane oscillator. In order to probe the oscillation mechanism more deeply, the effect of concentration, the change of position and kind of electrodes, as well as auxiliary experiments have been carried out and a generalizated mechanism has been given. The mechanism pointed out that under the condition of membrane reaction carrying to some extent, when the reaction rate is proportion to diffusion velocity, a regular periodic phenomenon could be produced. A comparison between simulation of experimental curves and mechanistic formula was also engaged. On the base of mono valence soap oscillator, various kinds of higher valence ones were formed by substitution or addition of transition metals. The change of pH, electric potential and conductivity during the reaction were monitored. With comparison study of the same kind of chemical oscillators, some conclusions were obtained from the consideration of the coordination between metal and acid radical.

Key words: pH, Interface, Oscillation, Oleic acid, Soap, Coordination