The Investigation Of Chemical Oscillatory Reactions Relating To Sodium Chlorite

This paper investigated the NaC102-I2-ethyl acetoacetate (EAA) and NaClO2-I2-malonic acid (MA) chemical oscillatory reaction systems by UV-vis spectrophotometric method and online infrared spectrum. The reaction of I2-EAA was also studied by online infrared spectrum.In the system of NaC102-I2-EAA, the chemical oscillatory reaction has an induced period. The amplitude increases along with the increase of the reaction time. Finally, the oscillation ceases gradually. The initial concentrations of sodium chlorite, iodine, ethyl acetoacetate and sulfuric acid have great influence on the oscillation. It was observed that the number of oscillations was decreasing along with the increase of the sodium chlorite's or ethyl acetoacetate's initial concentration. On the other hand, the number of oscillations was increasing along with the increase of the iodine's initial concentration without adding starch at 290nm. The oscillation phenomenon can also be observed at 350nm and 460nm by adding starch. The oscillation became more obvious by adding starch than that observed without adding starch at 290nm. As increasing the pH of the solution, the number of oscillations decreased and the amplitude increased. The equations of the amplitude and the period of oscillation changing with initial concentrations of various substances were obtained by differentiating and curve fitting of the oscillatory curves which were got in the experiments.In the system of NaC102-I2-MA, the chemical oscillatory reaction also has an induced period. The amplitude increases along with the increase of the reaction time. Finally, the oscillation ceases gradually. The initial concentrations of sodjum chlorite, iodine, malonic acid and sulfuric acid have great influence on the oscillation. When the initial concentration of sodium chlorite or iodine increased, the number of oscillations increased gradually, the amplitude decreased and the period of oscillation shortened gradually without adding starch at 290nm. On the other hand, an opposite phenomenon appeared as increasing the malonic acid's concentration. The oscillation phenomenon can also be observed at 360nm and 460nm by adding starch. The oscillation became more obvious by adding starch than that observed without adding starch at 290nm. As increasing the pH of the solution, the reaction rate decreased. The equations of the amplitude and the period of oscillation changing with initial concentrations of various substances were obtained by differentiating and curve fitting of the oscillatory curves which were got in the experiments.The reaction of I2-EAA was investigated by online infrared spectrum analysis. Four intermediates were detected during the reaction. The intermediates were identified through the infrared spectrum analysis. The enolization of ethyl acetoacetate was the key step of the reaction.