ASTM D5191-22

Standard Test Method for Vapor Pressure of Petroleum Products and Liquid Fuels (Mini Method)

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 mL to 10 mL), and requires about 7 min to complete the test.
SCOPE
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 and liquid fuels, including automotive spark-ignition fuels with or without oxygenates and with ethanol blends up to 85 % (volume fraction) (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 kPa and 130 kPa (1.0 psi 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 mL to 10 mL. No account is made for dissolved water in the sample.  
Note 1: The precision (see Section 16) using 1 L containers was determined in a 2003 interlaboratory study (ILS);2 the precision using 250 mL containers was determined in a 2016 ILS.3
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 ILS conducted in 1988, 1991, 2003, and 2016 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 °C 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 15).  
1.2 This test method is suitable for calculation of the dry vapor pressure equivalent (DVPE) of gasoline and gasoline-oxygenate blends by means of a correlation equation (see Eq 1 in 14.2). The calculated DVPE very closely approximates the dry vapor pressure that would be obtained on the same material when tested by Test Method D4953.  
1.3 The values stated in SI units are to be regarded as standard. The values given in parentheses after SI units are provided for information only and are not considered standard.  
1.4 WARNING—Mercury has been designated by many regulatory agencies as a hazardous substance that can cause serious medical issues. Mercury, or its vapor, has been demonstrated to be hazardous to health and corrosive to materials. Use Caution when handling mercury and mercury-containing products. See the applicable product Safety Data Sheet (SDS) for additional information. The potential exists that selling mercury or mercury-containing products, or both, is prohibited by local or national law. Users must determine legality of sales in their location.  
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. For specific safety warning statements, see 7.2 through 7.8.  
1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 30-Jun-2022
• ICS: 75.080 - Petroleum products in general
• Technical Committee: D02 - Petroleum Products, Liquid Fuels, and Lubricants
• Drafting Committee: D02.08 - Volatility

Relations

• Refers: ASTM D6299-23a - Standard Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measurement System Performance
• Effective Date: 01-Dec-2023
• Refers: ASTM D2892-23 - Standard Test Method for Distillation of Crude Petroleum (15-Theoretical Plate Column)
• Effective Date: 01-Nov-2023
• Refers: ASTM D5842-23 - Standard Practice for Sampling and Handling of Fuels for Volatility Measurement
• Effective Date: 01-Oct-2023
• Refers: ASTM D2892-20 - Standard Test Method for Distillation of Crude Petroleum (15-Theoretical Plate Column)
• Effective Date: 01-Jun-2020
• Refers: ASTM D4953-20 - Standard Test Method for Vapor Pressure of Gasoline and Gasoline-Oxygenate Blends (Dry Method)
• Effective Date: 01-May-2020
• Refers: ASTM D5842-19 - Standard Practice for Sampling and Handling of Fuels for Volatility Measurement
• Effective Date: 01-Nov-2019
• Refers: ASTM D5798-19b - Standard Specification for Ethanol Fuel Blends for Flexible-Fuel Automotive Spark-Ignition Engines
• Effective Date: 01-Jul-2019
• Refers: ASTM D5798-19a - Standard Specification for Ethanol Fuel Blends for Flexible-Fuel Automotive Spark-Ignition Engines
• Effective Date: 01-May-2019
• Refers: ASTM D5798-19 - Standard Specification for Ethanol Fuel Blends for Flexible-Fuel Automotive Spark-Ignition Engines
• Effective Date: 01-Feb-2019
• Refers: ASTM D5798-18a - Standard Specification for Ethanol Fuel Blends for Flexible-Fuel Automotive Spark-Ignition Engines
• Effective Date: 01-Dec-2018
• Refers: ASTM D6378-18a - Standard Test Method for Determination of Vapor Pressure (VP<inf>X</inf>) of Petroleum Products, Hydrocarbons, and Hydrocarbon-Oxygenate Mixtures (Triple Expansion Method)
• Effective Date: 01-Dec-2018
• Refers: ASTM D5798-18 - Standard Specification for Ethanol Fuel Blends for Flexible-Fuel Automotive Spark-Ignition Engines
• Effective Date: 01-Oct-2018
• Refers: ASTM D6378-18 - Standard Test Method for Determination of Vapor Pressure (VP<inf>X</inf>) of Petroleum Products, Hydrocarbons, and Hydrocarbon-Oxygenate Mixtures (Triple Expansion Method)
• Effective Date: 01-Jun-2018
• Refers: ASTM D2892-18 - Standard Test Method for Distillation of Crude Petroleum (15-Theoretical Plate Column)
• Effective Date: 01-Apr-2018
• Refers: ASTM D6299-17b - Standard Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measurement System Performance
• Effective Date: 15-Dec-2017

Overview

ASTM D5191-22 sets the standard test method for determining the vapor pressure of petroleum products and liquid fuels-particularly using the “mini method”-through automated vapor pressure instruments. Vapor pressure is a vital physical property that affects the safety, transportation, and regulatory compliance of volatile fuels such as gasoline and gasoline-oxygenate blends. Regulations and product specifications frequently set vapor pressure limits to ensure performance and environmental safety. ASTM D5191-22 offers a rapid, precise procedure applicable to various samples, including automotive spark-ignition fuels with or without oxygenates and ethanol blends up to 85% by volume.

Key Topics

• Vapor Pressure Measurement: Specifies the determination of total vapor pressure exerted in a vacuum by volatile petroleum products and fuels, including those with ethanol blends up to 85% by volume.
• Test Method Scope: Applicable to fuels with boiling points above 0°C (32°F), with vapor pressures between 7 kPa and 130 kPa (1.0 psi to 18.6 psi) at 37.8°C (100°F), and using a vapor-to-liquid ratio of 4:1.
• Small Sample Size and Fast Turnaround: Requires only 1 mL to 10 mL of liquid fuel and typically completes measurement in about 7 minutes.
• Equipment and Precision: Utilizes automated instruments with pressure transducers and thermostatic chambers, delivering higher precision compared to other test methods like ASTM D4953.
• Dry Vapor Pressure Equivalent (DVPE): Facilitates calculation of DVPE for gasoline and gasoline-oxygenate blends for close approximation with other standardized methods.
• Safety Considerations: Includes warnings for hazardous materials such as mercury and emphasizes the need for appropriate laboratory practices and regulatory awareness.

Applications

• Regulatory Compliance: Supports government and industry requirements for maximum allowable vapor pressures in fuels, crucial for environmental and operational safety.
• Quality Control and Blending: Provides refineries, fuel blenders, and testing laboratories a means to check volatility specifications in finished fuels, ensuring products meet regulatory and performance criteria.
• Fuel Formulation: Assists in developing and verifying gasoline formulations, including blends with ethanol or other oxygenates, ensuring optimal volatility and engine performance.
• Research and Testing: Used in laboratory settings for the evaluation of new fuel products, process optimization, and the adoption of alternative blendstocks.
• Rapid Decision Making: The fast execution of the mini method supports timely adjustments in fuel production and distribution.

Related Standards

For comprehensive fuel testing and handling, ASTM D5191-22 references and relates to several other standards:

• ASTM D4953: Standard Test Method for Vapor Pressure of Gasoline and Gasoline-Oxygenate Blends (Dry Method)
• ASTM D4057, D4177, D4306: Sampling methods for petroleum and petroleum products
• ASTM D5842, D5854: Fuel sample handling for volatility measurement
• ASTM D6377: Vapor Pressure of Crude Oil (Expansion Method)
• ASTM D6378: Vapor Pressure (Triple Expansion Method) of Petroleum Products, Hydrocarbons, and Mixtures
• IP 481 (EN 13016-1): Air Saturated Vapour Pressure of Crude Oil

Practical Value

ASTM D5191-22 is crucial for the fuel industry, regulatory authorities, and laboratories needing fast, accurate vapor pressure data to meet specifications, ensure environmental compliance, and safeguard fuel distribution and performance. The mini method’s efficiency, precision, and flexibility make it a preferred choice for routine fuel testing and regulatory reporting worldwide. By conforming to international standardization principles, this test method supports interoperability and acceptance in global fuel markets.

Keywords: ASTM D5191-22, vapor pressure, petroleum products, liquid fuels, gasoline, ethanol blends, DVPE, volatility, fuel testing, regulatory compliance, mini method.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D5191 − 22
Standard Test Method for
Vapor Pressure of Petroleum Products and Liquid Fuels
(Mini Method)
This standard is issued under the fixed designation D5191; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope* oxygenate blends by means of a correlation equation (see Eq 1
in 14.2). The calculated DVPE very closely approximates the
1.1 This test method covers the use of automated vapor
dryvaporpressurethatwouldbeobtainedonthesamematerial
pressure instruments to determine the total vapor pressure
when tested by Test Method D4953.
exerted in vacuum by air-containing, volatile, liquid petroleum
products and liquid fuels, including automotive spark-ignition 1.3 The values stated in SI units are to be regarded as
fuels with or without oxygenates and with ethanol blends up to standard. The values given in parentheses after SI units are
85 % (volume fraction) (see Note 1). This test method is provided for information only and are not considered standard.
suitable for testing samples with boiling points above 0 °C
1.4 WARNING—Mercury has been designated by many
(32 °F) that exert a vapor pressure between 7 kPa and 130 kPa
regulatory agencies as a hazardous substance that can cause
(1.0 psi and 18.6 psi) at 37.8 °C (100 °F) at a vapor-to-liquid
serious medical issues. Mercury, or its vapor, has been dem-
ratio of 4:1. Measurements are made on liquid sample sizes in
onstrated to be hazardous to health and corrosive to materials.
the range from 1 mL to 10 mL. No account is made for
Use Caution when handling mercury and mercury-containing
dissolved water in the sample.
products. See the applicable product Safety Data Sheet (SDS)
for additional information. The potential exists that selling
NOTE 1—The precision (see Section 16) using 1 L containers was
determined in a 2003 interlaboratory study (ILS); the precision using
mercury or mercury-containing products, or both, is prohibited
250 mL containers was determined in a 2016 ILS.
by local or national law. Users must determine legality of sales
NOTE 2—Samples can also be tested at other vapor-to-liquid ratios,
in their location.
temperatures,andpressures,buttheprecisionandbiasstatementsneednot
apply. 1.5 This standard does not purport to address all of the
NOTE 3—The ILS conducted in 1988, 1991, 2003, and 2016 to
safety concerns, if any, associated with its use. It is the
determine the precision statements in Test Method D5191 did not include
responsibility of the user of this standard to establish appro-
any crude oil in the sample sets. Test Method D6377, as well as IP 481,
priate safety, health, and environmental practices and deter-
have been shown to be suitable for vapor pressure measurements of crude
mine the applicability of regulatory limitations prior to use.
oils.
For specific safety warning statements, see 7.2 through 7.8.
1.1.1 Some gasoline-oxygenate blends may show a haze
1.6 This international standard was developed in accor-
when cooled to 0 °C to 1 °C. If a haze is observed in 8.5,it
dance with internationally recognized principles on standard-
shall be indicated in the reporting of results. The precision and
ization established in the Decision on Principles for the
bias statements for hazy samples have not been determined
Development of International Standards, Guides and Recom-
(see Note 15).
mendations issued by the World Trade Organization Technical
1.2 This test method is suitable for calculation of the dry
Barriers to Trade (TBT) Committee.
vapor pressure equivalent (DVPE) of gasoline and gasoline-
2. Referenced Documents
This test method is under the jurisdiction of ASTM Committee D02 on 2.1 ASTM Standards:
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of
D2892 Test Method for Distillation of Crude Petroleum
Subcommittee D02.08 on Volatility.
(15-Theoretical Plate Column)
Current edition approved July 1, 2022. Published August 2022. Originally
D4057 Practice for Manual Sampling of Petroleum and
approved in 1991. Last previous edition approved in 2020 as D5191 – 20. DOI:
10.1520/D5191-22.
Petroleum Products
Supporting data have been filed at ASTM International Headquarters and may
beobtainedbyrequestingResearchReportRR:D02-1619.ContactASTMCustomer
Service at [e-mail]. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
ResearchReportIP394(EN13016-1)andIP619(EN13016-3)2016,available contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
fromtheEnergyInstitute,61NewCavendishStreet,LondonW1G7AR,UK,email: Standards volume information, refer to the standard’s Document Summary page on
[e-mail]. the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D5191 − 22
D4177 Practice for Automatic Sampling of Petroleum and chamber, or a test chamber with a moveable piston that
Petroleum Products expands the volume after sample introduction, the internal
D4306 Practice for Aviation Fuel Sample Containers for volume of which is five times that of the total test specimen
Tests Affected by Trace Contamination introduced into the chamber. After introduction into the test
D4953 Test Method for Vapor Pressure of Gasoline and chamber, the test specimen is allowed to reach thermal equi-
Gasoline-Oxygenate Blends (Dry Method) librium at the test temperature, 37.8 °C (100 °F). The resulting
D5798 Specification for Ethanol Fuel Blends for Flexible- rise in pressure in the chamber is measured using a pressure
Fuel Automotive Spark-Ignition Engines transducer sensor and indicator. Only total pressure measure-
D5842 Practice for Sampling and Handling of Fuels for ments (sum of the partial pressure of the sample and the partial
Volatility Measurement pressure of the dissolved air) are used in this test method,
D5854 Practice for Mixing and Handling of Liquid Samples although some instruments can measure the absolute pressure
of Petroleum and Petroleum Products of the sample as well.
D6299 Practice for Applying Statistical Quality Assurance
4.2 The measured total vapor pressure is converted to a dry
and Control Charting Techniques to Evaluate Analytical
vapor pressure equivalent (DVPE) by use of a correlation
Measurement System Performance
equation (see Eq 1 in 14.2).
D6377 Test Method for Determination of Vapor Pressure of
Crude Oil: VPCR (Expansion Method)
x
5. Significance and Use
D6378 Test Method for Determination of Vapor Pressure
5.1 Vapor pressure is a very important physical property of
(VP ) of Petroleum Products, Hydrocarbons, and
X
volatile liquids.
Hydrocarbon-Oxygenate Mixtures (Triple Expansion
5.2 The vapor pressure of gasoline and gasoline-oxygenate
Method)
blends is regulated by various government agencies.
D7717 Practice for Preparing Volumetric Blends of Dena-
tured Fuel Ethanol and Gasoline Blendstocks for Labora-
5.3 Specifications for volatile petroleum products generally
tory Analysis
include vapor pressure limits to ensure products of suitable
2.2 IP Standard:
volatility performance.
IP 481 Test Method for Determination of the Air Saturated
5 5.4 This test method is more precise than Test Method
Vapour Pressure (ASVP) of Crude Oil
D4953,usesasmallsamplesize(1 mLto10 mL),andrequires
3. Terminology
about 7 min to complete the test.
3.1 Definitions:
6. Apparatus
3.1.1 fuel ethanol (Ed75–Ed85), n—blend of ethanol and
6.1 Vapor Pressure Apparatus—The type of apparatus suit-
hydrocarbon,ofwhichtheethanolportionisnominally75 %to
85 % by volume denatured fuel ethanol. able for use in this test method employs a small volume test
chamber incorporating a transducer for pressure measurements
3.2 Definitions of Terms Specific to This Standard:
and associated equipment for thermostatically controlling the
3.2.1 absolute vapor pressure, n—the pressure of the air-
chamber temperature and for evacuating the test chamber prior
freesample.Itiscalculatedfromthetotalvaporpressureofthe
to sample introduction or expanding the volume after sample
sample by subtracting out the partial pressure of the dissolved
introduction by a moveable piston.
air.
6.1.1 Thetestchambershallbedesignedtocontainbetween
3.2.2 dry vapor pressure equivalent (DVPE), n—a value
5 mL and 50 mL of liquid and vapor and be capable of
calculated by a correlation equation (see 14.2) from the total
maintaining a vapor-to-liquid ratio between 3.95 to 1.00 and
vapor pressure.
4.05 to 1.00.
3.2.2.1 Discussion—The DVPE is expected to be equivalent
NOTE 4—The test chamber employed by the instruments used in
to the value obtained on the sample by Test Method D4953,
generating the precision and bias statements were constructed of stainless
Procedure A.
steel, aluminum, or brass.
3.2.3 total vapor pressure (P ), n—the observed pressure
NOTE 5—Test chambers exceeding a 15 mL capacity can be used, but
tot
the precision and bias statements (see Section 16) are not known to apply.
measured in the experiment that is the sum of the partial
pressure of the sample and the partial pressure of the dissolved
6.1.2 The pressure transducer shall have a minimum opera-
air.
tional range from 0 kPa to 177 kPa (0 psi to 25.7 psi) with a
minimum resolution of 0.1 kPa (0.01 psi) and a minimum
3.3 Abbreviations:
accuracy of 60.8 kPa (60.12 psi). The pressure measurement
3.3.1 DVPE—dry vapor pressure equivalent
system shall include associated electronics and readout devices
3.3.2 P —total vapor pressure
tot
to display the resulting pressure reading.
4. Summary of Test Method
6.1.3 A thermostatically controlled heater shall be used to
maintain the test chamber at 37.8 °C 6 0.1 °C (100 °F 6
4.1 A known volume of chilled, air-saturated sample is
0.2 °F) for the duration of the vapor pressure measurement.
introduced into a thermostatically controlled, evacuated test
6.1.4 A platinum resistance thermometer shall be used for
measuring the temperature of the test chamber with a resolu-
Available from Energy Institute, 61 New Cavendish St., London, W1G 7AR,
U.K., http://www.energyinst.org. tion of 0.1 °C (0.2 °F) and an accuracy of 0.1 °C (0.2 °F).
D5191 − 22
A
TABLE 1 Accepted Reference Value (ARV) and Acceptable Testing Range for Reference Fluids Analyzed in the 2003 ILS
Recommended Instrument Acceptable Testing Range for
ARV [P ] ± Uncertainty,
tot
Reference Fluid Manufacturer Tolerance, Reference Fuel [P ],
tot
(kPa)
(kPa) (kPa)
Pentane 112.8 ± 0.2 ± 1.0 112.8 ± 1.2 (111.6 to 114.0)
2,2 Dimethylbutane 74.1 ± 0.2 ± 1.0 74.1 ± 1.2 (72.9 to 75.3)
2,3 Dimethylbutane 57.1 ± 0.2 ± 1.0 57.1 ± 1.2 (55.9 to 58.3)
Recommended Instrument Acceptable Testing Range for
ARV [P ] ± Uncertainty,
tot
Reference Fluid Manufacturer Tolerance, Reference Fuel [P ],
tot
(psi)
(psi) (psi)
Pentane 16.36 ± 0.03 ± 0.14 16.36 ± 0.17 (16.19 to 16.53)
2,2 Dimethylbutane 10.75 ± 0.03 ± 0.14 10.75 ± 0.17 (10.58 to 10.92)
2,3 Dimethylbutane 8.28 ± 0.03 ± 0.14 8.28 ± 0.17 (8.11 to 8.45)
A
Supporting data have been filed at ASTM International Headquarters and may be obtained by requesting Research Report RR:D02-1619. Contact ASTM Customer
Service at [e-mail].
6.1.5 Thevaporpressureapparatusshallhaveprovisionsfor specifications are available. Lower purities can be used,
provided it is first ascertained that the reagent is of sufficient
introduction of the test specimen into an evacuated test
purity to permit its use without lessening the accuracy of the
chamber, or into a test chamber by a moveable piston, and for
determination.
the cleaning or purging of the chamber following or preceding
7.1.1 The chemicals in sections 7.2, 7.3, 7.4, 7.7, and 7.8
the test.
(blended by mass with pentane) are suggested for verification
6.2 Vacuum Pump, capable of reducing the pressure in the
of instrument performance (see Section 11), based on the
test chamber to less than 0.01 kPa (0.001 psi) absolute.
reference fuels analyzed in the 2003 interlaboratory study
2 7
(ILS) (see Table 1) and 2014 interlaboratory study (ILS) (see
6.3 Syringe, (optional, depending on sample introduction
Table 2). Such reference fuels are not to be used for instrument
mechanism employed with each instrument) gas-tight, 1 mLto
calibration. Table 1 and Table 2 identify the accepted reference
20 mLcapacity with a 61 % or better accuracy and a 61%or
value (ARV) and uncertainty limits, as well as the acceptable
better precision. If a syringe is used to measure the sample
testing range for each of the reference fuels listed.
volume, the capacity of the syringe should not exceed two
NOTE 6—Verification fluids reported by 28 of the 29 D5191 data set
times the volume of the test specimen being dispensed.
participants in the 2003 ILS included the following (with number of data
sets identified in parenthesis): 2,2-dimethylbutane (18), cyclopentane (5),
6.4 Iced Water Bath, Refrigerator, or Air Bath, for chilling
pentane (2), 2,3-dimethylbutane (1), 3-methylpentane (1), and methanol
the samples and syringe to temperatures between 0 °C to 1 °C
(1).
(32 °F to 34 °F).
7.2 Cyclopentane, (Warning—Cyclopentane is flammable
6.5 Pressure Measuring Device, capable of measuring local
and a health hazard).
station pressure with an accuracy of 0.20 kPa (0.03 psi), or
7.3 2,2-Dimethylbutane, (Warning—2,2-dimethylbutane is
better, at the same elevation relative to sea level as the
flammable and a health hazard).
apparatus in the laboratory.
7.4 2,3-Dimethylbutane, (Warning—2,3-dimethylbutane is
6.5.1 When a mercury barometer is not used as the pressure
flammable and a health hazard).
measuring device, the calibration of the pressure measuring
7.5 Methanol, (Warning—Methanol is flammable and a
device employed shall be periodically checked (with traceabil-
health hazard).
ity to a nationally recognized standard) to ensure that the
device remains within the required accuracy specified in 6.5. 7.6 2-Methylpentane, (Warning—2-methylpentane is flam-
mable and a health hazard).
6.6 McLeodVacuumGageorCalibratedElectronicVacuum
7.7 Pentane, (Warning—Pentane is flammable and a health
Measuring Device for Calibration, to cover at least the range
hazard).
from 0.01 kPa to 0.67 kPa (0.1 mm Hg to 5 mm Hg). The
calibration of the electronic vacuum measuring device shall be
7.8 Toluene, (Warning—Toluene is flammable and a health
regularly verified in accordance with the annex section on hazard).
Vacuum Sensors (A6.3) of Test Method D2892.
ACS Reagent Chemicals, Specifications and Procedures for Reagents and
7. Reagents and Materials
Standard-Grade Reference Materials, American Chemical Society, Washington,
DC. For suggestions on the testing of reagents not listed by theAmerican Chemical
7.1 Purity of Reagents—Use chemicals of at least 99 %
Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset,
purity for verification of instrument performance (see Section U.K., and the United States Pharmacopeia and National Formulary, U.S. Pharma-
copeial Convention, Inc. (USPC), Rockville, MD.
11). Unless otherwise indicated, it is intended that all reagents
Supporting data have been filed at ASTM International Headquarters and may
conform to the specifications of the Committee on Analytical
beobtainedbyrequestingResearchReportRR:D02-1805.ContactASTMCustomer
Reagents of the American Chemical Society where such Service at [e-mail].
D5191 − 22
A
TABLE 2 Accepted Reference Value (ARV) and Acceptable Tolerance Range for Reference Fluids Analyzed in the 2014 ILS
Acceptable Tolerance Range for
Reference Fluid
ARV [P ] ± Expanded Uncertainty, Single Result on
tot
Reference Fluid Standard Deviation (kPa)
(kPa) Reference Fluid [P ],
tot
Determined in ILS
(kPa)
Cyclopentane 72.97 ± 0.21 0.58 72.97 ± 1.95 (71.02 to 74.92)
22.0/78.0 (m/m) Blend of Pentane/Toluene 46.45 ± 0.13 0.36 46.45 ± 1.21 (45.24 to 47.66)
44.0/56.0 (m/m) Blend of Pentane/Toluene 68.78 ± 0.23 0.63 68.78 ± 2.10 (66.68 to 70.88)
68.5/31.5 (m/m) Blend of Pentane/Toluene 88.58 ± 0.21 0.58 88.58 ± 1.95 (86.63 to 90.53)
Acceptable Tolerance Range for
Reference Fluid
ARV [P ] ± Expanded Uncertainty, Single Result on
tot
Reference Fluid Standard Deviation (psi)
(psi) Reference Fluid [P ],
tot
Determined in ILS
(psi)
Cyclopentane 10.58 ± 0.03 0.08 10.58 ± 0.28 (10.30 to 10.86)
22.0/78.0 (m/m) Blend of Pentane/Toluene 6.74 ± 0.02 0.05 6.74 ± 0.18 (6.56 to 6.92)
44.0/56.0 (m/m) Blend of Pentane/Toluene 9.98 ± 0.03 0.09 9.98 ± 0.30 (9.68 to 10.28)
68.5/31.5 (m/m) Blend of Pentane/Toluene 12.85 ± 0.03 0.08 12.85 ± 0.28 (12.57 to 13.13)
A
Supporting data have been filed at ASTM International Headquarters and may be obtained by requesting Research Report RR:D02-1805. Contact ASTM Customer
Service at [e-mail].
statements were derived using the first test specimen withdrawn from
7.9 Cyclopentane, 98.0 minimum purity (Warning—
250 mL or 1 L containers.
Cyclopentane is flammable and a health hazard).
8.1.5 Protect samples from excessive temperatures prior to
8. Sampling
testing. This can be accomplished by storage in an appropriate
8.1 General Requirements: ice bath or refrigerator.
8.1.1 The extreme sensitivity of vapor pressure measure-
8.1.6 Donottestsamplesstoredinleakycontainers.Discard
ments to losses through evaporation and the resulting changes
and obtain a new sample if leaks are detected.
in composition is such as to require the utmost precaution and
8.2 Sampling Handling Temperature—Place the sample
the most meticulous care in the drawing and handling of
container and contents in an ice bath or refrigerator to the 0 °C
samples.
to 1 °C (32 °F to 34 °F) range prior to opening the sample
8.1.2 Obtain samples and test specimens in accordance with
container. Allow sufficient time to reach this temperature.
Practice D4057, D4177, D4306, D5842,or D5854 when
NOTE 9—One way to verify the sample temperature is by direct
appropriate, except do not use the Sampling by Water Dis-
measurement of the temperature of a similar liquid in a similar container
placement section for fuels containing oxygenates. Use either
placed in the cooling bath or refrigerator at the same time as the sample.
250 mL or 1 L (1 qt) sized containers filled between 70 % and
Alternatively, temperature-monitoring studies conducted by laboratories
80 % with sample.
have determined the minimum amount of time necessary to achieve the
required temperature requirements stated in 8.2, based upon typical
8.1.2.1 Samplesincontainersofothersizes,asprescribedin
sample receipt temperatures and cooling capacities of the instrumentation
8.1.2, may be used with the same ullage requirement but
employed by the laboratory on samples included in such studies. The
precision can be affected.
results of such studies have subsequently been applied to additional
samples submitted for analysis. Typical minimum time durations reported
NOTE 7—The 2003 ILS indicated that there was no statistically
by laboratories have ranged between approximately 30 min and 45 min,
observable bias detected between 250 mL and 1 L containers.
however, laboratories choosing this option need to determine the mini-
8.1.3 To determine conformance with specifications, or
mumcoolingtimerequiredfortheirspecificoperationbyconductingtheir
own temperature-monitoring study.
regulations, or both, it may be necessary to prepare laboratory
handblendsofgasolineblendstocksanddenaturedfuelethanol
8.3 Verification of Sample Container Filling—With the
for testing purposes, including vapor pressure. If necessary,
sample at a temperature of 0 °C to 1 °C, take the container
then, a hand blend sample, prepared carefully in accordance
from the cooling bath or refrigerator, and wipe dry with
with a procedure such as that described in Practice D7717,
absorbent material. If the container is not transparent, unseal it
shall be considered suitable for the performance of this test.
and using a suitable gage, confirm that the sample volume
This hand blend, once prepared, shall then be considered
equals 70 % to 80 % of the container capacity (see Note 10). If
equivalent to the ‘sample or samples,’ referred to in 8.1.4
the sample is contained in a transparent glass container, verify
through 8.5 of this Sampling section, as well as in subsequent
that the container is 70 % to 80 % full by suitable means (see
sections of this test method.
Note 10).
8.1.4 Perform the vapor pressure determination on the first
8.3.1 Discardthesampleifthecontainerisfilledtolessthan
test specimen withdrawn from a sample container. Do not use
70 %, by volume, of the container capacity.
the remaining sample in the container for a second vapor
8.3.2 If the container is more than 80 % by volume full,
pressure determination. If a second determination is necessary,
pour out enough sample to bring the container contents within
obtain a new sample.
the 70 % to 80 % by volume range. Do not return any sample
NOTE 8—The effect of taking more than one test specimen from the
to the container once it has been withdrawn.
samesamplecontainerwasevaluatedaspartofthe2003ILS. Aprecision
8.3.3 Reseal the container if necessary, and return the
effect was observed between the first and second replicates taken from
both the 1 L and 250 mL containers evaluated. The current precision sample container to the cooling bath or refrigerator.
D5191 − 22
NOTE 10—For non-transparent containers, one way to confirm that the
10.1.1 Perform a calibration check of the transducer, as
sample volume equals 70 % to 80 % of the container capacity is to use a
indicated from the verification of instrument performance (see
dipstick that has been pre-marked to indicate the 70 % and 80 % container
Section 11) and quality control checks (see Section 12). The
capacities. The dipstick should be of such material that it shows wetting
calibration of the transducer is checked using two reference
after being immersed and withdrawn from the sample. To confirm the
points, zero pressure (<0.1 kPa) and the ambient barometric
sample volume, insert the dipstick into the sample container so that it
to
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D5191 − 20 D5191 − 22
Standard Test Method for
Vapor Pressure of Petroleum Products and Liquid Fuels
(Mini Method)
This standard is issued under the fixed designation D5191; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope*
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 and liquid fuels, including automotive spark-ignition fuels with or
without oxygenates and with ethanol blends up to 85 % (volume fraction) (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 kPa and 130 kPa (1.0 psi 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 mL to 10 mL.
No account is made for dissolved water in the sample.
NOTE 1—The precision (see Section 16) using 1 L containers was determined in a 2003 interlaboratory study (ILS); the precision using 250 mL containers
was determined in a 2016 ILS.
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 ILS conducted in 1988, 1991, 2003, and 2016 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 °C 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 15).
1.2 This test method is suitable for calculation of the dry vapor pressure equivalent (DVPE) of gasoline and gasoline-oxygenate
blends by means of a correlation equation (see Eq 1 in 14.2). The calculated DVPE very closely approximates the dry vapor
pressure that would be obtained on the same material when tested by Test Method D4953.
1.3 The values stated in SI units are to be regarded as standard. The values given in parentheses after SI units are provided for
information only and are not considered standard.
1.4 WARNING—Mercury has been designated by many regulatory agencies as a hazardous substance that can cause serious
medical issues. Mercury, or its vapor, has been demonstrated to be hazardous to health and corrosive to materials. Use Caution
This test method is under the jurisdiction of ASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcommittee
D02.08 on Volatility.
Current edition approved May 1, 2020July 1, 2022. Published May 2020August 2022. Originally approved in 1991. Last previous edition approved in 20192020 as D5191
– 19.– 20. DOI: 10.1520/D5191-20.10.1520/D5191-22.
Supporting data have been filed at ASTM International Headquarters and may be obtained by requesting Research Report RR:D02-1619. Contact ASTM Customer
Service at [e-mail].
Research Report IP 394 (EN 13016-1) and IP 619 (EN 13016-3) 2016, available from the Energy Institute, 61 New Cavendish Street, London W1G 7AR, UK, email:
[e-mail].
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D5191 − 22
when handling mercury and mercury-containing products. See the applicable product Safety Data Sheet (SDS) for additional
information. The potential exists that selling mercury or mercury-containing products, or both, is prohibited by local or national
law. Users must determine legality of sales in their location.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of
regulatory limitations prior to use. For specific safety warning statements, see 7.2 through 7.8.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D2892 Test Method for Distillation of Crude Petroleum (15-Theoretical Plate Column)
D4057 Practice for Manual Sampling of Petroleum and Petroleum Products
D4177 Practice for Automatic Sampling of Petroleum and Petroleum Products
D4306 Practice for Aviation Fuel Sample Containers for Tests Affected by Trace Contamination
D4953 Test Method for Vapor Pressure of Gasoline and Gasoline-Oxygenate Blends (Dry Method)
D5798 Specification for Ethanol Fuel Blends for Flexible-Fuel Automotive Spark-Ignition Engines
D5842 Practice for Sampling and Handling of Fuels for Volatility Measurement
D5854 Practice for Mixing and Handling of Liquid Samples of Petroleum and Petroleum Products
D6299 Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measure-
ment System Performance
D6377 Test Method for Determination of Vapor Pressure of Crude Oil: VPCR (Expansion Method)
x
D6378 Test Method for Determination of Vapor Pressure (VP ) of Petroleum Products, Hydrocarbons, and Hydrocarbon-
X
Oxygenate Mixtures (Triple Expansion Method)
D7717 Practice for Preparing Volumetric Blends of Denatured Fuel Ethanol and Gasoline Blendstocks for Laboratory Analysis
2.2 IP Standard:
IP 481 Test Method for Determination of the Air Saturated Vapour Pressure (ASVP) of Crude Oil
3. Terminology
3.1 Definitions:
3.1.1 fuel ethanol (Ed75–Ed85), n—blend of ethanol and hydrocarbon, of which the ethanol portion is nominally 75 % to 85 %
by volume denatured fuel ethanol.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 absolute vapor pressure, n—the pressure of the air-free sample. It is calculated from the total vapor pressure of the sample
by subtracting out the partial pressure of the dissolved air.
3.2.2 dry vapor pressure equivalent (DVPE), n—a value calculated by a correlation equation (see 14.2) from the total vapor
pressure.
3.2.2.1 Discussion—
The DVPE is expected to be equivalent to the value obtained on the sample by Test Method D4953, Procedure A.
3.2.3 total vapor pressure (P ),n—the observed pressure measured in the experiment that is the sum of the partial pressure of the
tot
sample and the partial pressure of the dissolved air.
3.3 Abbreviations:
3.3.1 DVPE—dry vapor pressure equivalent
3.3.2 P —total vapor pressure
tot
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Available from Energy Institute, 61 New Cavendish St., London, W1G 7AR, U.K., http://www.energyinst.org.
D5191 − 22
4. Summary of Test Method
4.1 A known volume of chilled, air-saturated sample is introduced into a thermostatically controlled, evacuated test chamber, or
a test chamber with a moveable piston that expands the volume after sample introduction, the internal volume of which is five times
that of the total test specimen introduced into the chamber. After introduction 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 Eq 1 in 14.2).
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 mL to 10 mL), and requires about 7 min
to complete the test.
6. Apparatus
6.1 Vapor Pressure Apparatus—The type of apparatus suitable for use in this test method employs a small volume test chamber
incorporating a transducer for pressure measurements and associated equipment for thermostatically controlling the chamber
temperature and for evacuating the test chamber prior to sample introduction or expanding the volume after sample introduction
by a moveable piston.
6.1.1 The test chamber shall be designed to contain between 5 mL and 50 mL of liquid and vapor and be capable of maintaining
a vapor-to-liquid ratio between 3.95 to 1.00 and 4.05 to 1.00.
NOTE 4—The test chamber employed by the instruments used in generating the precision and bias statements were constructed of stainless steel,
aluminum, or brass.
NOTE 5—Test chambers exceeding a 15 mL capacity can be used, but the precision and bias statements (see Section 16) are not known to apply.
6.1.2 The pressure transducer shall have a minimum operational range from 0 kPa to 177 kPa (0 psi to 25.7 psi) with a minimum
resolution of 0.1 kPa (0.01 psi) and a minimum accuracy of 60.8 kPa (60.12 psi). The pressure measurement system shall include
associated electronics and readout devices to display the resulting pressure reading.
6.1.3 A thermostatically controlled heater shall be used to maintain the test chamber at 37.8 °C 6 0.1 °C (100 °F 6 0.2 °F) for
the duration of the vapor pressure measurement.
6.1.4 A platinum resistance thermometer shall be used for measuring the temperature of the test chamber with a resolution of
0.1 °C (0.2 °F) and an accuracy of 0.1 °C (0.2 °F).
6.1.5 The vapor pressure apparatus shall have provisions for introduction of the test specimen into an evacuated test chamber, or
into a test chamber by a moveable piston, and for the cleaning or purging of the chamber following or preceding the test.
6.2 Vacuum Pump, capable of reducing the pressure in the test chamber to less than 0.01 kPa (0.001 psi) absolute.
6.3 Syringe, (optional, depending on sample introduction mechanism employed with each instrument) gas-tight, 1 mL to 20 mL
D5191 − 22
A
TABLE 1 Accepted Reference Value (ARV) and Acceptable Testing Range for Reference Fluids Analyzed in the 2003 ILS
Recommended Instrument Acceptable Testing Range for
ARV [P ] ± Uncertainty,
tot
Reference Fluid Manufacturer Tolerance, Reference Fuel [P ],
tot
(kPa)
(kPa) (kPa)
Pentane 112.8 ± 0.2 ± 1.0 112.8 ± 1.2 (111.6 to 114.0)
2,2 Dimethylbutane 74.1 ± 0.2 ± 1.0 74.1 ± 1.2 (72.9 to 75.3)
2,3 Dimethylbutane 57.1 ± 0.2 ± 1.0 57.1 ± 1.2 (55.9 to 58.3)
Recommended Instrument Acceptable Testing Range for
ARV [P ] ± Uncertainty,
tot
Reference Fluid Manufacturer Tolerance, Reference Fuel [P ],
tot
(psi)
(psi) (psi)
Pentane 16.36 ± 0.03 ± 0.14 16.36 ± 0.17 (16.19 to 16.53)
2,2 Dimethylbutane 10.75 ± 0.03 ± 0.14 10.75 ± 0.17 (10.58 to 10.92)
2,3 Dimethylbutane 8.28 ± 0.03 ± 0.14 8.28 ± 0.17 (8.11 to 8.45)
A
Supporting data have been filed at ASTM International Headquarters and may be obtained by requesting Research Report RR:D02-1619. Contact ASTM Customer
Service at [e-mail].
capacity with a 61 % or better accuracy and a 61 % or better precision. If a syringe is used to measure the sample volume, the
capacity of the syringe should not exceed two times the volume of the test specimen being dispensed.
6.4 Iced Water Bath, Refrigerator, or Air Bath, for chilling the samples and syringe to temperatures between 0 °C to 1 °C (32 °F
to 34 °F).
6.5 Pressure Measuring Device, capable of measuring local station pressure with an accuracy of 0.20 kPa (0.03 psi), or better, at
the same elevation relative to sea level as the apparatus in the laboratory.
6.5.1 When a mercury barometer is not used as the pressure measuring device, the calibration of the pressure measuring device
employed shall be periodically checked (with traceability to a nationally recognized standard) to ensure that the device remains
within the required accuracy specified in 6.5.
6.6 McLeod Vacuum Gage or Calibrated Electronic Vacuum Measuring Device for Calibration, to cover at least the range from
0.01 kPa to 0.67 kPa (0.1 mm Hg to 5 mm Hg). The calibration of the electronic vacuum measuring device shall be regularly
verified in accordance with the annex section on Vacuum Sensors (A6.3) of Test Method D2892.
7. Reagents and Materials
7.1 Purity of Reagents—Use chemicals of at least 99 % purity for verification of instrument performance (see Section 11). Unless
otherwise indicated, it is intended that all reagents conform to the specifications of the Committee on Analytical Reagents of the
American Chemical Society where such specifications are available. Lower purities can be used, provided it is first ascertained
that the reagent is of sufficient purity to permit its use without lessening the accuracy of the determination.
7.1.1 The chemicals in sections 7.2, 7.3, 7.4, 7.7, and 7.8 (blended by mass with pentane) are suggested for verification of
instrument performance (see Section 11), based on the reference fuels analyzed in the 2003 interlaboratory study (ILS) (see Table
1) and 2014 interlaboratory study (ILS) (see Table 2). Such reference fuels are not to be used for instrument calibration. Table 1
and Table 2 identify the accepted reference value (ARV) and uncertainty limits, as well as the acceptable testing range for each
of the reference fuels listed.
NOTE 6—Verification fluids reported by 28 of the 29 D5191 data set participants in the 2003 ILS included the following (with number of data sets
identified in parenthesis): 2,2-dimethylbutane (18), cyclopentane (5), pentane (2), 2,3-dimethylbutane (1), 3-methylpentane (1), and methanol (1).
7.2 Cyclopentane, (Warning—Cyclopentane is flammable and a health hazard).
7.3 2,2-Dimethylbutane, (Warning—2,2-dimethylbutane is flammable and a health hazard).
ACS Reagent Chemicals, Specifications and Procedures for Reagents and Standard-Grade Reference Materials, American Chemical Society, Washington, DC. For
suggestions on the testing of reagents not listed by the American Chemical Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and
the United States Pharmacopeia and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville, MD.
Supporting data have been filed at ASTM International Headquarters and may be obtained by requesting Research Report RR:D02-1805. Contact ASTM Customer
Service at [e-mail].
D5191 − 22
A
TABLE 2 Accepted Reference Value (ARV) and Acceptable Tolerance Range for Reference Fluids Analyzed in the 2014 ILS
Acceptable Tolerance Range for
Reference Fluid
ARV [P ] ± Expanded Uncertainty, Single Result on
tot
Reference Fluid Standard Deviation (kPa)
(kPa) Reference Fluid [P ],
tot
Determined in ILS
(kPa)
Cyclopentane 72.97 ± 0.21 0.58 72.97 ± 1.95 (71.02 to 74.92)
22.0/78.0 (m/m) Blend of Pentane/Toluene 46.45 ± 0.13 0.36 46.45 ± 1.21 (45.24 to 47.66)
44.0/56.0 (m/m) Blend of Pentane/Toluene 68.78 ± 0.23 0.63 68.78 ± 2.10 (66.68 to 70.88)
68.5/31.5 (m/m) Blend of Pentane/Toluene 88.58 ± 0.21 0.58 88.58 ± 1.95 (86.63 to 90.53)
Acceptable Tolerance Range for
Reference Fluid
ARV [P ] ± Expanded Uncertainty, Single Result on
tot
Reference Fluid Standard Deviation (psi)
(psi) Reference Fluid [P ],
tot
Determined in ILS
(psi)
Cyclopentane 10.58 ± 0.03 0.08 10.58 ± 0.28 (10.30 to 10.86)
22.0/78.0 (m/m) Blend of Pentane/Toluene 6.74 ± 0.02 0.05 6.74 ± 0.18 (6.56 to 6.92)
44.0/56.0 (m/m) Blend of Pentane/Toluene 9.98 ± 0.03 0.09 9.98 ± 0.30 (9.68 to 10.28)
68.5/31.5 (m/m) Blend of Pentane/Toluene 12.85 ± 0.03 0.08 12.85 ± 0.28 (12.57 to 13.13)
A
Supporting data have been filed at ASTM International Headquarters and may be obtained by requesting Research Report RR:D02-1805. Contact ASTM Customer
Service at [e-mail].
7.4 2,3-Dimethylbutane, (Warning—2,3-dimethylbutane is flammable and a health hazard).
7.5 Methanol, (Warning—Methanol is flammable and a health hazard).
7.6 2-Methylpentane, (Warning—2-methylpentane is flammable and a health hazard).
7.7 Pentane, (Warning—Pentane is flammable and a health hazard).
7.8 Toluene, (Warning—Toluene is flammable and a health hazard).
7.9 Cyclopentane, 98.0 minimum purity (Warning—Cyclopentane is flammable and a health hazard).
8. Sampling
8.1 General Requirements:
8.1.1 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 drawing and handling of samples.
8.1.2 Obtain samples and test specimens in accordance with Practice D4057, D4177, D4306, D5842, or D5854 when appropriate,
except do not use the Sampling by Water Displacement section for fuels containing oxygenates. Use either 250 mL or 1 L (1 qt)
sized containers filled between 70 % and 80 % with sample.
8.1.2.1 Samples in containers of other sizes, as prescribed in 8.1.2, may be used with the same ullage requirement but precision
can be affected.
NOTE 7—The 2003 ILS indicated that there was no statistically observable bias detected between 250 mL and 1 L containers.
8.1.3 To determine conformance with specifications, or regulations, or both, it may be necessary to prepare laboratory hand blends
of gasoline blendstocks and denatured fuel ethanol for testing purposes, including vapor pressure. If necessary, then, a hand blend
sample, prepared carefully in accordance with a procedure such as that described in Practice D7717, shall be considered suitable
for the performance of this test. This hand blend, once prepared, shall then be considered equivalent to the ‘sample or samples,’
referred to in 8.1.4 through 8.5 of this Sampling section, as well as in subsequent sections of this test method.
8.1.4 Perform the vapor pressure determination on the first test specimen withdrawn from a sample container. Do not use the
remaining sample in the container for a second vapor pressure determination. If a second determination is necessary, obtain a new
sample.
D5191 − 22
NOTE 8—The effect of taking more than one test specimen from the same sample container was evaluated as part of the 2003 ILS. A precision effect
was observed between the first and second replicates taken from both the 1 L and 250 mL containers evaluated. The current precision statements were
derived using the first test specimen withdrawn from 250 mL or 1 L containers.
8.1.5 Protect samples from excessive temperatures prior to testing. This can be accomplished by storage in an appropriate ice bath
or refrigerator.
8.1.6 Do not test samples stored in leaky containers. Discard and obtain a new sample if leaks are detected.
8.2 Sampling Handling Temperature—Place the sample container and contents in an ice bath or refrigerator to the 0 °C to 1 °C
(32 °F to 34 °F) range prior to opening the sample container. Allow sufficient time to reach this temperature.
NOTE 9—One way to verify the sample temperature is by direct measurement of the temperature of a similar liquid in a similar container placed in the
cooling bath or refrigerator at the same time as the sample. Alternatively, temperature-monitoring studies conducted by laboratories have determined the
minimum amount of time necessary to achieve the required temperature requirements stated in 8.2, based upon typical sample receipt temperatures and
cooling capacities of the instrumentation employed by the laboratory on samples included in such studies. The results of such studies have subsequently
been applied to additional samples submitted for analysis. Typical minimum time durations reported by laboratories have ranged between approximately
30 min and 45 min, however, laboratories choosing this option need to determine the minimum cooling time required for their specific operation by
conducting their own temperature-monitoring study.
8.3 Verification of Sample Container Filling—With the sample at a temperature of 0 °C to 1 °C, take the container from the cooling
bath or refrigerator, and wipe dry with absorbent material. If the container is not transparent, unseal it and using a suitable gage,
confirm that the sample volume equals 70 % to 80 % of the container capacity (see Note 10). If the sample is contained in a
transparent glass container, verify that the container is 70 % to 80 % full by suitable means (see Note 10).
8.3.1 Discard the sample if the container is filled to less than 70 %, by volume, of the container capacity.
8.3.2 If the container is more than 80 % by volume full, pour out enough sample to bring the container contents within the 70 %
to 80 % by volume range. Do not return any sample to the container once it has been withdrawn.
8.3.3 Reseal the container if necessary, and return the sample container to the cooling bath or refrigerator.
NOTE 10—For non-transparent containers, one way to confirm that the sample volume equals 70 % to 80 % of the container capacity is to use a dipstick
that has been pre-marked to indicate the 70 % and 80 % container capacities. The dipstick should be of such material that it shows wetting after being
immersed and withdrawn from the sample. To confirm the sample volume, insert the dipstick into the sample container so that it touches the bottom of
the container at a perpendicular angle, before removing the dipstick. For transparent containers, using a marked ruler or by comparing the sample
container to a like container which has the 70 % and 80 % levels clearly marked, has been found suitable.
8.4 Air Saturation of the Sample in the Sample Container:
8.4.1 Transparent Containers Only—Since 8.3 does not require that the sample container be opened to verify the sample capacity,
it is necessary to unseal the cap momentarily before resealing it, so that samples in transparent containers are treated the same as
samples in non-transparen
...