Practice of Kinetics (Comprehensive Chemical Kinetics, Volume 1)

;,124 EXPERIMENTAL METHODS FOR FAST REACTIONSDriver gasIIDiaphragmvObservationpointsFig. 3. Schematic arrangement for the shock tube.sure is instantaneous. This is a shock wave, and, if their energy were not graduallydissipated to the medium, all sounds would eventually become shock waves a sufficientlylarge distance from the source. Shock waves are used in the study of thekinetics of gas reactions most conveniently in a shock tube. A good general accountof the application of the technique to chemical kinetics has been given by Bauer”.Other general treatments give varying amounts of theoretical and practical de-In principle, the design of a shock tube is very simple; it is illustrated in Fig. 3.Typically, a smooth metal or glass tube about twenty feet long and a few inches indiameter is divided into two compartments by a thin diaphragm made of a suitablematerial such as cellophane or aluminum foil. About a third of the tube comprisesa high-pressure region containing the “driver” gas, often hydrogen or helium. Theremainder of the tube is a comparatively low-pressure region containing the gasmixture whose reactions are to be studied. The experiment is started by puncturingFig. 4. Becker’sso~model for the formation of a shock wave.