ASTM D5191 Test Method for Vapor Pressure of Petroleum Products (Mini Method)
4. Summary of Test Method
4.1 A known volume of chilled, air-saturated sample is introduced into an evacuated, thermostatically controlled test chamber, the internal volume of which is five times that of the total test specimen introduced into the chamber. After injection into the test chamber, the test specimen is allowed to reach thermal equilibrium at the test temperature, 37.8°C (100°F). The resulting rise in pressure in the chamber is measured using a pressure transducer sensor and indicator. Only total pressure measurements (sum of the partial pressure of the sample and the partial pressure of the dissolved air) are used in this test method, although some instruments can measure the absolute pressure of the sample as well.
4.2 The measured total vapor pressure is converted to a dry vapor pressure equivalent (DVPE) by use of a correlation equation (see 13.2).
5. Significance and Use
5.1 Vapor pressure is a very important physical property of volatile liquids.
5.2 The vapor pressure of gasoline and gasoline-oxygenate blends is regulated by various government agencies.
5.3 Specifications for volatile petroleum products generally include vapor pressure limits to ensure products of suitable volatility performance.
5.4 This test method is more precise than Test Method D4953, uses a small sample size (1 to 10 mL), and requires about 7 min to complete the test.
