IEC
REPORTS
brane is punctured by needle activated by a device sealed into the system, and bursts, sending a shock wave rapidly down the tube. This wave passes through the second membrane and into the other end chamber, containing a mixture of air and hydrocarbon which react under the impact. To eliminate some of the complexities of the problem, a simple hydrocarbon, propane, is used instead of gasoline. Quartz windows in the tube make it possible to make ultraviolet absorption spectrographic measurements. The Ford setup differs from previously reported instruments in that it permits determination of a full absorption curve in the ultraviolet spectrum, not merely the absorption at one wave length. The instrumentation consists of:
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HEADQUARTERS FOR SCALES For further information, circle number 20 AT on Readers' Service Card, page 139 A
20 A
INDUSTRIAL AND ENGINEERING CHEMISTRY
(1) facilities to measure shock wave velocity; (2) facilities to time the observation of the ultraviolet spectrum relative to the passage of the shock wave through the hydrocarbon-air mixture; (3) facilities to measure continuously the pressure in the combustion section; (4) a high-intensity, short-duration light source to furnish the light pulse for the ultraviolet absorption spectroscopy. As the shock wave progresses down the tube it passes two shock wave detection stations a known distance apart. The time of transit (of the order of 500 microseconds) between these two stations is measured and the velocity computed. The signal from the last detection station is also fed to an electronic time delay generator. The output of this time delay generator is used to fire the high-intensity, short-duration light source. By this means ultraviolet absorption spectra may be taken at predetermined time intervals after the shock wave has passed through the combustion mixture. The absorption spectra are taken in about 10 microseconds. The pressure in the combustion section is continuously measured after the shock wave has passed through the combustion mixture. T h e pressure is read out on a cathode ray oscilloscope and the trace photographed. Another part of the research pro-
