vapor pressure: the pressure exerted by a vapor; often understood to mean saturated vapor pressure (the vapor pressure of a vapor in contact with its liquid form)
The pressure exerted by the molecules of a given vapor In meteorology, it is considered as the part of total atmospheric pressure due to the water vapor content It is independent of other gases or vapors
The pressure of a given saturated vapor is a function of the temperature only, and may be measured by introducing a small quantity of the substance into a barometer and noting the depression of the column of mercury
A measure of a substance's propensity to evaporate, vapor pressure is the force per unit area exerted by vapor in an equilibrium state with surroundings at a given pressure It increases exponentially with an increase in temperature A relative measure of chemical volatility, vapor pressure is used to calculate water partition coefficients and volatilization rate constants
1 The pressure exerted by the molecules of a given vapor For a pure confined vapor, it is that vapor's pressure on the walls of its containing vessel; and for a vapor mixed with other vapors or gases, it is that vapor's contribution to the total pressure (i e , its partial pressure) Also called vapor tension
pressure of confined vapor in equilibrium with its liquid at a specified temperature; thus, a measure of a liquids volatility Vapor pressure of gasoline and other volatile petroleum products is commonly measured in accordance with test method ASTM D 323 (Reid vapor pressure) The apparatus is essentially a double-chambered bomb One chamber, fitted with a pressure gauge, contains air at atmospheric pressure; the other chamber is filled with the liquid sample The bomb is immersed in a 37 8°C (100°F) bath, and the resulting vapor pressure of the sample is recorded in pounds per square inch (psi) Reid vapor pressure is useful in predicting seasonal gasoline performance (e g , higher volatility is needed in cold weather, and lower volatility in hot weather), as well as the tendencies of gasolines, solvents, and other volatile petroleum products toward evaporative loss and fire hazard
Pressure exerted by a saturated vapor above its liquid in a closed container Important facts to remember: Vapor pressure of a substance at 100° F will always be higher than the vapor pressure of the substance at 60° F Vapor pressures reported on MSDS/s in mmHg are usually very low pressures; 760 mmHg is equivalent to 14 7 psi The lower the boiling point of a substance, the higher its vapor pressure
Vapor Pressure is the pressure of a vapor when in equilibrium with its liquid or solid form It is a measure of the tendency of a material to form a vapor The higher the vapor pressure, the higher the potential vapor concentration In general, a material with a high vapor pressure is more likely to be an inhalation or fire hazard than a similar material with a lower vapor pressure