ASTM D323 for vapor pressure of petroleum products (Reid method)
5. Apparatus
5.1 The required apparatus for Procedures A, C, and D is described in Annex A1. Apparatus for Procedure B is described in Annex A2.
6. Hazards
6.1 Gross errors can be obtained in vapor pressure measurements if the prescribed procedure is not followed carefully. The following list emphasizes the importance of strict adherence to the precautions given in the procedure:
6.1.1 Checking the Pressure Gage - Check all gages against a pressure measuring device (see A1.6) after each test to ensure higher precision of results (see 11.4). Read the gage while in a vertical position and after tapping it lightly.
6.1.2 Checking for Leaks - Check all apparatus before and during each test for both liquid and vapor leaks (see Note 7).
6.1.3 Sampling - Because initial sampling and the handling of samples will greatly affect the final results, employ the utmost precaution and the most meticulous care to avoid losses through evaporation and even slight changes in composition (see Section 7 and 11.1). In no case shall any part of the Reid apparatus itself be used as the sample container prior to actually conducting the test.
6.1.4 Purging the Apparatus - Thoroughly purge the pressure gage, the liquid chamber, and the vapor chamber to be sure that they are free of residual sample. This is most conveniently done at the end of the test in preparation for the next test (see 11.5 and 14.5).
6.1.5 Coupling the Apparatus - Carefully observe the requirements of 11.2.
6.1.6 Shaking the Apparatus - Shake the apparatus vigorously as directed to ensure equilibrium.
7. Sampling
7.1 The extreme sensitivity of vapor pressure measurements to losses through evaporation and the resulting changes in composition is such as to require the utmost precaution and the most meticulous care in the handling of samples. The provisions of this section shall apply to all samples for vapor pressure determinations, except as specifically excluded for samples having vapor pressures above 180 kPa (26 psi); see Section 18.
7.2 Sampling shall be done in accordance with Practice D4057.
7.3 Sample Container Size - The size of the sample container from which the vapor pressure sample is taken shall be 1 L (1 qt). It shall be 70 to 80 % filled with sample.
7.3.1 The present precision statement has been derived using samples in 1-L (1-qt) containers. However, samples taken in containers of other sizes as prescribed in Practice D4057 can be used if it is recognized that the precision could be affected. In the case of referee testing, the 1-L (1-qt) sample container shall be mandatory.
7.4 The Reid vapor pressure determination shall be performed on the first test specimen withdrawn from the sample container. The remaining sample in the container cannot be used for a second vapor pressure determination. If necessary, obtain a new sample.
7.4.1 Protect samples from excessive heat prior to testing.
7.4.2 Do not test samples in leaky containers. They should be discarded and new samples obtained.
7.5 Sampling Handling Temperature - In all cases, cool the sample container and contents to 0 to 1°C (32 to 34°F) before the container is opened. Sufficient time to reach this temperature shall be ensured by direct measurement of the temperature of a similar liquid in a like container placed in the cooling bath at the same time as the sample.
