ASTM D 5191a

1.1 This test method covers the use of automated vapor pressure instruments to determine the total vapor pressure exerted in vacuum by air-containing, volatile, liquid petroleum products, including automotive spark-ignition fuels with or without oxygenates (see Note 1). This test method is suitable for testing samples with boiling points above 0°C (32°F) that exert a vapor pressure between 7 and 130 kPa (1.0 and 18.6 psi) at 37.8°C (100°F) at a vapor-to-liquid ratio of 4:1. Measurements are made on liquid sample sizes in the range from 1 to 10 mL. No account is made for dissolved water in the sample. Note 1 -An interlaboratory study was conducted in 2008 involving 11 different laboratories submitting 15 data sets and 15 different samples of ethanol-fuel blends containing 25 volume %, 50 volume %, and 75 volume % ethanol. The results indicated that the repeatability limits of these samples are with in the published repeatability of this test method. on this basis, it can be concluded that D5191 is applicable to ethanol-fuel blends such as Ed75 and Ed85 (Specification D5798) and other ethanol-fuel blends with greater than 10 v% ethanol. See ASTM RR: D02-1694 filed with ASTM for supporting data. Note 2 -Samples can also be tested at other vapor-to-liquid ratios, temperatures, and pressures, but the precision and bias statements need not apply. Note 3 -The interlaboratory studies conducted in 1988, 1991, and 2003 to determine the precision statements in Test Method D5191 did not include any crude oil in the sample sets. Test Method D6377, as well as IP 481, have been shown to be suitable for vapor pressure measurements of crude oils. 1.1.1 Some gasoline-oxygenate blends may show a haze when cooled to 0 to 1°C. If a haze is observed in 8.5, it shall be indicated in the reporting of results. The precision and bias statements for hazy samples have not been determined (see Note 16). 1.2 This test method is suitable for calcu ....(abbreviated)