Study of kinetics of a reaction by using spectrophotometric method

Information regarding the kinetics of many reactions has been obtained by using UV-Visible absorption spectroscopy. The progress of a reaction, i.e., change in the concentrations of the reactants or products can be followed spectrophotometrically if one of them is a light absorbing substance. For example, oxidation or reduction reaction of organic dyes can be easily followed by the absorption spectroscopy method, since the dyes are coloured compounds. In addition to organic and inorganic coloured compounds, some metal particles in their dispersed states show distinct colours. Therefore, formation of such particles from the reduction of metal ions by some reducing agent can also be studied by using UV-visible spectrophotometry. In this experiment we study first the formation of different sized gold particles in aqueous surfactant medium and then study the reduction of an organic dye, eosin, by sodium borohydride catalysed by these particles.