On the Flash Point of Liquid Fuels

Abstract

Velocity of propagation of combustion along the surface of inflammable liquid was measured at various temperatures. When liquid temperature is comparatively high, combustion propagates through vapor-air mixtures floating above the surface of the liquid. But as the temperature is lowered, the ratio of the density of vapor to that of air approaches to lower limit of ignition and a temperature is attained at which the vapor is so lean that the combustion can no longer propagate through this layer of vapor-air mixture, and the “combustion after vaporization” begins. At this stage, the liquid surface close to the flame front is heated to vaporize by the flame itself and after the vapor density at the layer adjacent to it attains to the lower limit of combustion, the flame propagates to this layer.
The boundary temperature between these two stages of propagation was considered to be a flash point and was measured with various liquids.