ASTM D2879 Vapor Pressure-Temperature Relationship and Initial Decomposition Temperature of Liquids by Isoteniscope
Vapor pressure, which gives an indication of a mixture's evaporation rate, has many important applications. For example, high vacuum oils require very low vapor pressures to prevent fouling of the vacuum system; hydraulic fluids require low vapor pressures to lessen the chance of cavitation; lubricating oils require low vapor pressures to lessen changes in viscosity and other properties during use. If vapor pressure is determined at a series of temperatures and the data is graphed (log vapor pressure vs. ºK-1), a deviation from linearity may indicate sample decomposition. This test determines vapor pressures of liquids.
The test sample is pipetted into the isoteniscope, heated to remove trapped gases, manipulated as per the method to create a pure vapor bubble and brought to the test temperature. The vapor pressure is determined and reported in mm Hg (torr). If a multi-temperature determination is requested, the vapor pressure is reported at the requested temperatures and graphed to allow analysis of the data.