Pressure measurements synchronized with high-speed motion picture records of flame propagation have been made in a transparent piston engine. The data show that the initial expansion speed of the flame front is close to that of a laminar flame. As the flame expands, its speed rapidly accelerates to a quasi-steady value comparable with that of the turbulent velocity fluctuations in the unburned gas. During the quasi-steady propagation phase, a significant fraction of the gas behind the visible front is unburned. Final burnout of the charge may be approximated by an exponential decay in time.The data have been analyzed in a model independent way to obtain a set of empirical equations for calculating mass burning rates in spark ignition engines. The burning equations contain three parameters: the laminar burning speed st, a characteristic speed at, and a characteristic length IT. The laminar burning speed is known from laboratory measurements. Tentative correlations relating u T and IT to engine geometry and operating variables have been derived from the engine data.

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Chlorpyrifos in the heterogeneous phase of the atmosphere is quickly removed by reaction with OH radicals (∼2 day) whereas its degradation product, chlorpyrifos oxon is more persistent.