VOLATILITY, IN ITS SIMPLEST DEFINITION, IS THE TENDENCY OF A LIQUID TO CHANGE INTO VAPOR. For fuels, lubricants, and other petroleum products, this tendency is measured in a variety of ways. Volatility parameters are related to the performance characteristics and/or safety of these materials. Among the various ways of determining the volatility properties of materials are: distillation, rate of evaporation measurement, flash point test, and vapor pressure determination. Distillation determines the temperatures required to evaporate known portions of the material, as well as the temperatures at which distillation begins and ends. Distillation also determines the temperature the boiling range of the materials. A volatility property particularly important in solvents and coating materilas is the rate of evaporation. The flash point of a liquid is the lowest temperature, corrected for barrometric pressures, at which application of an ignition source causes the vapor above the specimen to ignite. Vapor pressure is the force per unit area exerted on the walls of a closed container by the vaporized portion portion of the liquid material in the container.