AbstractA method is described for the measurement of relative rate constants for abstraction of hydrogen from ethylene at temperatures in the region of 750 K. The method is based on the effect of the addition of small quantities of propane and isobutane on the rates of formation of products in the thermal chain reactions of ethylene. On the assumption that methane and ethane are formed by the following reactions,measurements of the ratio of the rates of formation of methane and ethane in the presence and absence of the additive gave the following results:\documentclass{article}\pagestyle{empty}\begin{document}$$\log (k_7 /k_2) = (- 0.50 \pm 0.4) + (3200 \pm 1000)/2.3T$$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$$\log (k_8 /k_3) = (- 0.20 \pm 0.4) + (2800 \pm 1000)/2.3T$$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$$\log (k_{11} /k_2) = (- 0.97 \pm 0.4) + (4600 \pm 1000)/2.3T$$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$$\log (k_{12} /k_3) = (- 2.0 \pm 0.4) + (6300 \pm 1000)/2.3T$$\end{document}Values fork2andk3obtained from these ratios are compared with previous measurements.