ASTM E1194-07

Vapor pressure values can be used to predict volatilization rates (5). Vapor pressures, along with vapor-liquid partition coefficients (Henry’Law constant) are used to predict volatilization rates from liquids such as water. These values are thus particularly important for the prediction of the transport of a chemical in the environment (6).

1.1 This test method describes procedures for measuring the vapor pressure of pure liquid or solid compounds. Since no single technique is available to measure vapor pressures from 1 X 10^-11 to 100 kPa (approximately 10^-10 to 760 torr), two procedures are presented. An isoteniscope (standard) procedure for measuring vapor pressures of liquids from 1 X 10^-1 to 100 kPa (approximately 1 to 760 torr) is available in Test Method D 2879. A gas-saturation procedure for measuring vapor pressures from 1 X 10^-11 to 1 kPa (approximately 10^-10 to 10 torr) is presented in this test method. Both procedures are subjects of U.S. Environmental Protection Agency Test Guidelines.

1.2 These two methods were selected to provide data at normal environmental temperatures (10 to 60°C). At least three temperature values should be studied to allow definition of a vapor pressure-temperature correlation. Values determined should be based on temperature selections such that a measurement is made at 25°C (as recommended by IUPAC) (1), a value can be interpolated for 25°C, or a value can be reliably extrapolated for 25°C. Extrapolation to 25°C should be avoided if the temperature range tested includes a value at which a phase change occurs. Extrapolation to 25°C over a range larger than 10°C should also be avoided. The test methods were selected because of their extended range, simplicity, and general applicability (2). Examples of results produced by the gas-saturation procedure during an interlaboratory evaluation are given in Table 1. These data have been taken from Reference (3).

1.3 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.

1.4 This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.