FIRST referring to previous reports made on laboratory methods for measurement of volatility, the author states that data for a variety of gasolines, obtained by the equilibrium air-distillation method, have been analyzed recently in comparison with the distillation curves of these fuels as determined by the procedure practised by the American Society for Testing Materials. According to the author, this analysis appears to indicate a definite relationship between the results on volatility and those obtained by the standard A.S.T.M. distillation method, so that it seems possible to deduce from the latter with reasonable accuracy the information on volatility which is pertinent to satisfactory engine performance. It is stated also that volatility can be regarded as the tendency to escape into the vapor or gaseous state and this escaping tendency is determined by factors which must be precisely specified so that numerical values for volatility may have significance. Throughout the paper, the expression “air-fuel mixture” is used to indicate a mixture of air and gasoline supplied, while the term “air-vapor mixture” is applied to the resultant mixture of air and vapor formed when all or part of the liquid changes to vapor in the presence of air.
After stating that all the data on volatility were obtained with the Sligh equilibrium air-distillation apparatus, the author comments upon this equipment and describes its calibration, the method of using the equilibrium air-distillation apparatus, and the calculation of results. The experimental data are then analyzed. A chart for the estimation of volatility from the A.S.T.M. distillation curves is explained, and is used in testing the general correlation of results. In conclusion, it is said that the A.S.T.M. distillation curves give a true indication of the relative volatilities of gasolines.
Appendix 1 presents notes on fuel requirements for engine starting. Appendix 2 contains recomputed values for the lean explosive limits of gasolines.