CHAPTER 2 - EXPERIMENTAL TECHNIQUES

Abstract

Publisher Summary A variety of physical and chemical methods have been used to follow the progress of chemical reactions. These fall into two groups: (1) conventional techniques being used for reactions with half-lives, t1/2, of more than 30 sec, and (2) fast reaction techniques for reactions with half-lives down to 10-9 sec. When physical methods are used, it is first necessary to check that the change in physical property is proportional to the change in concentration, that is, that Beer's Law holds when spectrophotometric measurements are made. As a general rule, absorptiometric and, for gas-phase reactions, manometric methods are used whenever possible. Standard volumetric procedures have been used for a number of oxidation-reduction reactions between metal ions, when absorptiometric methods are not applicable. In the gas-phase reaction between hydrogen and iodine over the temperature range 283-508°C, reaction mixtures are first quenched by rapid cooling. The seal on the reaction vessel is then broken under dilute sodium hydroxide solution, and the iodide and iodine concentrations determined by standard procedures.