Practice of Kinetics (Comprehensive Chemical Kinetics, Volume 1)

92 EXPERIMENTAL METHODS FOR SLOW REACTIONSTo pumps-/'..------/\Magnet pole face(l2'diam)Fig. 64. The stirred flow reactor combined with ESR. From ref. 301.are in good agreement with other reported values300*299. Mulcahy et aL3" havemodified the 'set-up using a stirred-flow reactor to insure complete mixing of thereactants (Fig. 64), and they studied the reactionThe concentration of the 0 atoms was monitored just before and just after theRV. Nalbandyan302 has reviewed the use of this technique in combustion studies.Apart from investigation of reactions of hydrogen and oxygen atoms and OH radicals,it has been used to establish the site at which 0 attacks the complex molecule.The calibration methods and the sources of error involved in estimating the concentrationsof these atomic and diatomic species are discussed by several authors298,299.3034.4.4 Mass spectrometryAnother direct, and in this case, well established, method of following the courseof a reaction is by mass spectrometry. The application of mass spectrometry toanalysis of organic compounds has been dealt with by Beynon304 and Reed305and two volumes are concerned with the advances in this field3O6l3O7. The massspectrometry of free radicals has been reviewed by Cuthbert3O*.Apart from the direct following of the rate of a reaction, identification and quantitativeestimation of the transient species, the mass spectrometer may also be