ASTM D611-23

Standard Test Methods for Aniline Point and Mixed Aniline Point of Petroleum Products and Hydrocarbon Solvents

SIGNIFICANCE AND USE
5.1 The aniline point (or mixed aniline point) is useful as an aid in the characterization of pure hydrocarbons and in the analysis of hydrocarbon mixtures. Aromatic hydrocarbons exhibit the lowest, and paraffins the highest values. Cycloparaffins and olefins exhibit values that lie between those for paraffins and aromatics. In homologous series the aniline points increase with increasing molecular weight. Although it occasionally is used in combination with other physical properties in correlative methods for hydrocarbon analysis, the aniline point is most often used to provide an estimate of the aromatic hydrocarbon content of mixtures.
SCOPE
1.1 These test methods cover the determination of the aniline point of petroleum products and hydrocarbon solvents. Test Method A is suitable for transparent samples with an initial boiling point above room temperature and where the aniline point is below the bubble point and above the solidification point of the aniline-sample mixture. Test Method B, a thin-film method, is suitable for samples too dark for testing by Test Method A. Test Methods C and D are for samples that may vaporize appreciably at the aniline point. Test Method D is particularly suitable where only small quantities of sample are available. Test Method E describes a procedure using an automatic apparatus suitable for the range covered by Test Methods A and B.  
1.2 These test methods also cover the determination of the mixed aniline point of petroleum products and hydrocarbon solvents having aniline points below the temperature at which aniline will crystallize from the aniline-sample mixture.  
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this 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. Specific warning statements are given in Section 7.  
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-Apr-2023
• ICS: 71.080.01 - Organic chemicals in general
• ICS: 87.060.30 - Solvents
• Technical Committee: D02 - Petroleum Products, Liquid Fuels, and Lubricants
• Drafting Committee: D02.04.0D - Physical and Chemical Methods

Relations

• Refers: ASTM D1500-24 - Standard Test Method for ASTM Color of Petroleum Products (ASTM Color Scale)
• Effective Date: 01-Mar-2024
• Refers: ASTM D4175-23a - Standard Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
• Effective Date: 15-Dec-2023
• Refers: ASTM D4175-23e1 - Standard Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
• Effective Date: 01-Jul-2023
• Refers: ASTM E1-13 - Standard Specification for ASTM Liquid-in-Glass Thermometers
• Effective Date: 01-May-2013
• Refers: ASTM D1500-12 - Standard Test Method for ASTM Color of Petroleum Products (ASTM Color Scale)
• Effective Date: 01-Dec-2012
• Refers: ASTM D1500-07 - Standard Test Method for ASTM Color of Petroleum Products (ASTM Color Scale)
• Effective Date: 01-Dec-2007
• Refers: ASTM E1-07 - Standard Specification for ASTM Liquid-in-Glass Thermometers
• Effective Date: 01-Nov-2007
• Refers: ASTM E1-05 - Standard Specification for ASTM Liquid-in-Glass Thermometers
• Effective Date: 01-Nov-2005
• Refers: ASTM D1500-04a - Standard Test Method for ASTM Color of Petroleum Products (ASTM Color Scale)
• Effective Date: 01-Nov-2004
• Refers: ASTM D1500-04 - Standard Test Method for ASTM Color of Petroleum Products (ASTM Color Scale)
• Effective Date: 01-Jun-2004
• Refers: ASTM D1500-03 - Standard Test Method for ASTM Color of Petroleum Products (ASTM Color Scale)
• Effective Date: 01-Nov-2003
• Refers: ASTM E1-03a - Standard Specification for ASTM Liquid-in-Glass Thermometers
• Effective Date: 01-Nov-2003
• Refers: ASTM E1-03 - Standard Specification for ASTM Thermometers
• Effective Date: 10-May-2003
• Refers: ASTM D1500-02 - Standard Test Method for ASTM Color of Petroleum Products (ASTM Color Scale)
• Effective Date: 10-Nov-2002
• Refers: ASTM E1-98e1 - Standard Specification for ASTM Thermometers
• Effective Date: 10-Oct-2001

Overview

ASTM D611-23: Standard Test Methods for Aniline Point and Mixed Aniline Point of Petroleum Products and Hydrocarbon Solvents specifies procedures for determining the aniline point and mixed aniline point. These methods are widely used to estimate aromatic hydrocarbon content, key for the analysis and characterization of petroleum products and hydrocarbon solvents.

The standard covers multiple test methods appropriate for different sample types – including transparent, dark, volatile, and small-quantity samples. The test involves mixing controlled volumes of aniline with the sample, heating until miscibility, and then cooling to observe the temperature where phase separation occurs. The resulting "aniline point" value provides a practical indication of the mixture's aromatic content.

Key Topics

• Aniline Point: The minimum equilibrium solution temperature for equal volumes of aniline and petroleum or hydrocarbon solvent sample.
• Mixed Aniline Point: The minimum equilibrium solution temperature of a mixture of two volumes of aniline, one volume of sample, and one volume of n-heptane.
• Test Methods: ASTM D611-23 includes several approaches to accommodate sample characteristics:
  • Test Method A – for transparent samples above room temperature boiling point.
  • Test Method B – thin-film method for dark samples.
  • Test Methods C and D – for samples that vaporize readily or for small sample sizes.
  • Test Method E – automatic apparatus applying the principles of A and B.
• Safety Notes: Particular caution is advised when handling toxic chemicals like aniline and mercury. Users must follow appropriate safety, health, and environmental practices as outlined in the standard.
• Significance and Use:
  • Aromatic hydrocarbons have the lowest aniline points, paraffins the highest, with cycloparaffins and olefins in-between.
  • The aniline point increases with molecular weight in homologous series.
  • This test estimate the aromatic content of petroleum fractions efficiently, informing blending, quality control, and regulatory compliance.

Applications

ASTM D611-23 is referenced across the oil, gas, and chemical industries for:

• Fuel Characterization: Helps classify petroleum-based fuels, lubricants, and solvents by aromatic content, essential for process control and specification conformance.
• Quality Control: Enables rapid, standardized assessment of hydrocarbon blends during production and distribution.
• Material Compatibility: Informs decisions on material selection for storage and transport, as aromatic content impacts compatibility with seals, gaskets, and other fuel system components.
• Environmental and Safety Compliance: Supports determination of products that may be subject to tighter legislative controls due to aromatic hydrocarbon content.
• Analytical Support: Provides valuable data in research, formulations, and forensic analysis related to petroleum and hydrocarbon products.

Related Standards

• ASTM D1500: Standard Test Method for ASTM Color of Petroleum Products (ASTM Color Scale) – referenced for sample suitability in ASTM D611-23.
• ASTM D4175: Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants – definitions and terminology.
• ASTM E1: Specification for ASTM Liquid-in-Glass Thermometers – guidance on temperature measurement equipment.
• International Energy Institute Standards: The Energy Institute’s technically equivalent methods, commonly applied in global contexts, are referenced as harmonized with ASTM D611.

Conclusion

By complying with ASTM D611-23, organizations ensure consistent, reliable characterization of petroleum products and hydrocarbon solvents through standardized measurement of aniline and mixed aniline points. This enables efficient quality assurance and product classification, underpinning safe, optimized, and compliant operations in the petroleum and chemical sectors.

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: D611 − 23
Designation: 2/98 (2014)
Standard Test Methods for
Aniline Point and Mixed Aniline Point of Petroleum Products
1,2
and Hydrocarbon Solvents
This standard is issued under the fixed designation D611; 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* products. See the applicable product Safety Data Sheet (SDS)
for additional information. The potential exists that selling
1.1 These test methods cover the determination of the
mercury or mercury-containing products, or both, is prohibited
aniline point of petroleum products and hydrocarbon solvents.
by local or national law. Users must determine legality of sales
Test Method A is suitable for transparent samples with an
in their location.
initial boiling point above room temperature and where the
aniline point is below the bubble point and above the solidifi-
1.5 This standard does not purport to address all of the
cation point of the aniline-sample mixture. Test Method B, a
safety concerns, if any, associated with its use. It is the
thin-film method, is suitable for samples too dark for testing by
responsibility of the user of this standard to establish appro-
Test Method A. Test Methods C and D are for samples that may
priate safety, health, and environmental practices and deter-
vaporize appreciably at the aniline point. Test Method D is
mine the applicability of regulatory limitations prior to use.
particularly suitable where only small quantities of sample are
Specific warning statements are given in Section 7.
available. Test Method E describes a procedure using an
1.6 This international standard was developed in accor-
automatic apparatus suitable for the range covered by Test
dance with internationally recognized principles on standard-
Methods A and B.
ization established in the Decision on Principles for the
1.2 These test methods also cover the determination of the Development of International Standards, Guides and Recom-
mixed aniline point of petroleum products and hydrocarbon
mendations issued by the World Trade Organization Technical
solvents having aniline points below the temperature at which Barriers to Trade (TBT) Committee.
aniline will crystallize from the aniline-sample mixture.
2. Referenced Documents
1.3 The values stated in SI units are to be regarded as
standard. No other units of measurement are included in this
2.1 ASTM Standards:
standard.
D1500 Test Method for ASTM Color of Petroleum Products
(ASTM Color Scale)
1.4 WARNING—Mercury has been designated by many
regulatory agencies as a hazardous substance that can cause D4175 Terminology Relating to Petroleum Products, Liquid
Fuels, and Lubricants
serious medical issues. Mercury, or its vapor, has been dem-
onstrated to be hazardous to health and corrosive to materials. E1 Specification for ASTM Liquid-in-Glass Thermometers
Use caution when handling mercury and mercury-containing
3. Terminology
3.1 Definitions:
These test methods are under the jurisdiction of ASTM International Commit-
3.1.1 For definitions of terms used in this test method, refer
tee D02 on Petroleum Products, Liquid Fuels, and Lubricants and are the direct
to Terminology D4175.
responsibility of ASTM Subcommittee D02.04.0D on Physical and Chemical
Methods. The technically equivalent standard as referenced is under the jurisdiction
3.1.2 aniline point, n—the minimum equilibrium solution
of the Energy Institute Subcommittee SC-B-10.
temperature for equal volumes of aniline and sample.
Current edition approved May 1, 2023. Published May 2023. Originally
approved in 1941. Last previous edition approved in 2016 as D611 – 12 (2016).
DOI: 10.1520/D0611-23.
These test methods were adopted as a joint ASTM-IP standard in 1964.
2 3
This test method has been developed through the cooperative effort between For referenced ASTM standards, visit the ASTM website, www.astm.org, or
ASTM and the Energy Institute, London. ASTM and IP standards were approved by contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
ASTM and EI technical committees as being technically equivalent but that does not Standards volume information, refer to the standard’s Document Summary page on
imply both standards are identical. 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
D611 − 23
3.1.3 mixed aniline point, n—the minimum equilibrium 6.4 Pipets, or equivalent volume dispensing devices, ca-
solution temperature of a mixture of two volumes of aniline, pable of delivering volumes with capacities of 10 mL 6
one volume of sample, and one volume of n-heptane of 0.04 mL and 5 mL 6 0.02 mL, for use in the test.
specified purity.
6.5 Balance—A laboratory balance sensitive to 0.01 g, suit-
able for weighing the tube and sample when the sample cannot
4. Summary of Test Method
be pipetted conveniently.
4.1 Specified volumes of aniline and sample, or aniline and
6.6 Safety Goggles.
sample plus n-heptane, are placed in a tube and mixed
mechanically. The mixture is heated at a controlled rate until
6.7 Plastic Gloves, impervious to aniline.
the two phases become miscible. The mixture is then cooled at
7. Reagents
a controlled rate and the temperature at which two phases
separate is recorded as the aniline point or mixed aniline point.
7.1 Aniline (Warning—Aniline should not be pipetted di-
rectly by mouth because of its extreme toxicity. Aniline is also
5. Significance and Use
toxic by absorption through the skin even in very small
5.1 The aniline point (or mixed aniline point) is useful as an
quantities, and should be handled with great caution.) The
aid in the characterization of pure hydrocarbons and in the
aniline shall be sufficiently pure such that when tested with
analysis of hydrocarbon mixtures. Aromatic hydrocarbons
n-heptane according to Section 9, it shall give an aniline point
exhibit the lowest, and paraffins the highest values. Cyclopar-
of 69.3 °C 6 0.2 °C (156.7 °F 6 0.4 °F) as determined from
affins and olefins exhibit values that lie between those for
the average of two independent tests having a difference of not
paraffins and aromatics. In homologous series the aniline
more than 0.1 °C (0.2 °F). If the aniline point of heptane is
points increase with increasing molecular weight. Although it
higher than this specification, the aniline may be dried by
occasionally is used in combination with other physical prop-
distillation, where the first and last 10 % are discarded. If the
erties in correlative methods for hydrocarbon analysis, the
aniline point is lower, water may be added until the aniline
aniline point is most often used to provide an estimate of the
meets the specification.
aromatic hydrocarbon content of mixtures.
NOTE 3—It is estimated that approximately 400 ppm to 1400 ppm of
6. Apparatus
water in aniline is required to meet the heptane specification.
NOTE 4—As an alternative to distilling the aniline on the day of use, the
6.1 For details of the aniline point apparatus required for
aniline may be distilled as described in 7.1, collecting the distillate in
each method see:
ampoules, sealing the ampoules under vacuum or dry nitrogen, and storing
in a cool dark place for future use. Alternatively, distillate may be stored
Annex A1 for Test Method A
under dry nitrogen in a glass bottle or in single use ampoules kept in a
Annex A2 for Test Method B
Annex A3 for Test Method C cool, dark place. In either case, rigid precaution must be taken to avoid
Annex A4 for Test Method D
contamination from atmospheric moisture (Note 2). It is believed that
Annex A5 for Test Method E
under these conditions the aniline will remain unchanged for a period
exceeding 6 months.
NOTE 1—Alternative apparatus may be used, such as the U-tube method
for dark oils, provided it has been shown to give results of the same
7.2 Calcium Sulfate, anhydrous.
precision and accuracy as those described in the annexes.
7.3 n-Heptane, spectroscopic or HPLC grade. (Warning—
6.2 Heating and Cooling Bath—A suitable air bath, a
Flammable. Harmful if inhaled. Keep away from heat, sparks,
nonvolatile, transparent liquid bath, or an infrared lamp
and open flame. Keep container closed. Use with adequate
(250 W to 375 W), provided with means for controlling the
ventilation. Avoid prolonged breathing of vapor or spray mist.
rate of heating.
Avoid prolonged or repeated skin contact.)
NOTE 2—Water should not be used as either a heating or cooling
medium since aniline is hygroscopic and moist aniline will give erroneous 8. Sample
test results. For example, the aniline point of the n-heptane reagent as
8.1 Dry the sample by shaking vigorously for 3 min to
measured with aniline containing 0.1 % by volume water is approximately
5 min with about 10 % by volume of a suitable drying agent
0.5 °C (0.9 °F) higher than that measured with dry aniline. If the aniline
point is below the dew point of the atmosphere, pass a slow stream of dry such as anhydrous calcium sulfate or anhydrous sodium
inert gas into the aniline point tube to blanket the aniline-sample mixture.
sulfate. Reduce the viscosity of viscous samples by warming to
6.3 Thermometers, or other temperature sensing devices, a temperature below that which would cause the loss of light
such as thermocouples or platinum resistance thermometers
ends or the dehydration of the drying agent. Remove any
that cover the temperamental range of interest and can provide suspended drying agent by use of a centrifuge or by filtration.
equivalent or better accuracy and precision, may be used in
Heat samples containing separated wax until they are homo-
place of the thermometers having the following ranges and geneous and keep heated during filtration or centrifugation to
conforming to the requirements of the designated ASTM or IP
ensure against separation of wax. When suspended water is
specification:
visibly present and the sample material is known to dissolve
less than 0.03 % by mass of water, the use of a centrifuge for
ASTM
Range IP
(Specification E1)
the removal of suspended water is an acceptable procedure.
−38 °C to + 42 °C (−36.5 °F 33C, 33F 20C
9. Procedure for Aniline Point
to + 107.5 °F)
25 °C to 105 °C (77 °F to 221 °F) 34C, 34F 21C 9.1 The following methods, to be used as applicable, are
90 °C to 170 °C (194 °F to 338 °F) 35C, 35F 59C
covered as follows:
D611 − 23
9.1.1 Test Method A, described in detail in Annex A1, is 12. Precision and Bias
applicable to clear samples or to samples not darker than No.
12.1 The precision of these test methods as obtained by
6.5 ASTM color, as determined by Test Method D1500, having
statistical examination of interlaboratory test results is as
initial boiling points well above the expected aniline point.
follows:
9.1.2 Test Method B, described in detail in Annex A2, is
12.1.1 Repeatability—The difference between successive
applicable to light-colored samples, moderately dark samples,
test results (two average temperatures obtained in a series of
and to very dark samples. It is suitable for samples that are too
observations as described in Section 11 obtained by the same
dark to be tested by Test Method A.
operator with the same apparatus under constant operating
conditions on identical test material, would in the long run, in
9.1.3 Test Method C, described in detail in Annex A3, is
applicable to clear samples or to samples not darker than No. the normal and correct operation of the test method, exceed the
6.5 ASTM color, as determined by Test Method D1500, having following values only in one case in twenty:
initial boiling points sufficiently low as to give incorrect aniline
Repeatability
Aniline point of:
point readings by Test Method A, for example, aviation
Clear, light-colored samples 0.16 °C (0.3 °F)
gasoline.
A
Moderately dark to very dark samples 0.3 °C (0.6 °F)
9.1.4 Test Method D, described in detail in Annex A4, is Mixed aniline point of:
A
Clear, light-colored samples 0.16 °C (0.3 °F)
applicable to the same type of sample as Test Method C. It is
A
Moderately dark to very dark samples 0.3 °C (0.6 °F)
particularly useful when only limited quantities of sample are
available. A
Not determined from recent cooperative tests; however, the ratios with those
given in the 1953 version are believed to apply.
9.1.5 Test Method E is applicable when using automatic
apparatus in accordance with the instructions in Annex A5.
12.1.2 Reproducibility—The difference between two single
and independent results, obtained by different operators, work-
10. Procedure for Mixed Aniline Point
ing in different laboratories on identical test material, would in
the long run, in the normal and correct operation of the test
10.1 This procedure is applicable to samples having aniline
method, exceed the following values only in one case in
points below the temperature at which aniline crystallizes from
twenty:
the mixture. Deliver 10 mL of aniline (Warning—See 7.1),
Reproducibility
5 mL of sample, and 5 mL of n-heptane into a clean, dry
Anilin
...

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: D611 − 12 (Reapproved 2016) D611 − 23
Designation: 2/98 (2014)
Standard Test Methods for
Aniline Point and Mixed Aniline Point of Petroleum Products
1,2
and Hydrocarbon Solvents
This standard is issued under the fixed designation D611; 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 Scope*
1.1 These test methods cover the determination of the aniline point of petroleum products and hydrocarbon solvents. Test Method
A is suitable for transparent samples with an initial boiling point above room temperature and where the aniline point is below the
bubble point and above the solidification point of the aniline-sample mixture. Test Method B, a thin-film method, is suitable for
samples too dark for testing by Test Method A. Test Methods C and D are for samples that may vaporize appreciably at the aniline
point. Test Method D is particularly suitable where only small quantities of sample are available. Test Method E describes a
procedure using an automatic apparatus suitable for the range covered by Test Methods A and B.
1.2 These test methods also cover the determination of the mixed aniline point of petroleum products and hydrocarbon solvents
having aniline points below the temperature at which aniline will crystallize from the aniline-sample mixture.
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 WARNING—Mercury has been designated by many regulatory agencies as a hazardous materialsubstance that can cause
central nervous system, kidney and liver damage. serious medical issues. Mercury, or its vapor, may has been demonstrated to be
hazardous to health and corrosive to materials. Caution should be taken Use caution when handling mercury and mercury
containing mercury-containing products. See the applicable product Material Safety Data Sheet (MSDS) for details and EPA’s
website—http://www.epa.gov/mercury/faq.htm—for additional information. Users should be aware (SDS) for additional informa-
tion. The potential exists that selling mercury and/or mercury containing products into your state or country may be prohibited by
law.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 and healthsafety, health, and environmental practices and determine
the applicability of regulatory limitations prior to use. Specific warning statements are given in Section 7.
These test methods are under the jurisdiction of ASTM International Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and are the direct responsibility
of ASTM Subcommittee D02.04.0D on Physical and Chemical Methods. The technically equivalent standard as referenced is under the jurisdiction of the Energy Institute
Subcommittee SC-B-10.
Current edition approved Oct. 1, 2016May 1, 2023. Published November 2016May 2023. Originally approved in 1941. Last previous edition approved in 20122016 as
D611 – 12.D611 – 12 (2016). DOI: 10.1520/D0611-12R16.10.1520/D0611-23.
These test methods were adopted as a joint ASTM-IP standard in 1964.
This test method has been developed through the cooperative effort between ASTM and the Energy Institute, London. ASTM and IP standards were approved by ASTM
and EI technical committees as being technically equivalent but that does not imply both standards are identical.
*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
D611 − 23
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:
D1500 Test Method for ASTM Color of Petroleum Products (ASTM Color Scale)
D4175 Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
E1 Specification for ASTM Liquid-in-Glass Thermometers
3. Terminology
3.1 Definitions:
3.1.1 For definitions of terms used in this test method, refer to Terminology D4175.
3.1.2 aniline point, n—the minimum equilibrium solution temperature for equal volumes of aniline and sample.
3.1.3 mixed aniline point, n—the minimum equilibrium solution temperature of a mixture of two volumes of aniline, one volume
of sample, and one volume of n-heptane of specified purity.
4. Summary of Test Method
4.1 Specified volumes of aniline and sample, or aniline and sample plus n-heptane, are placed in a tube and mixed mechanically.
The mixture is heated at a controlled rate until the two phases become miscible. The mixture is then cooled at a controlled rate
and the temperature at which two phases separate is recorded as the aniline point or mixed aniline point.
5. Significance and Use
5.1 The aniline point (or mixed aniline point) is useful as an aid in the characterization of pure hydrocarbons and in the analysis
of hydrocarbon mixtures. Aromatic hydrocarbons exhibit the lowest, and paraffins the highest values. Cycloparaffins and olefins
exhibit values that lie between those for paraffins and aromatics. In homologous series the aniline points increase with increasing
molecular weight. Although it occasionally is used in combination with other physical properties in correlative methods for
hydrocarbon analysis, the aniline point is most often used to provide an estimate of the aromatic hydrocarbon content of mixtures.
6. Apparatus
6.1 For details of the aniline point apparatus required for each method see:
Annex A1 for Test Method A
Annex A2 for Test Method B
Annex A3 for Test Method C
Annex A4 for Test Method D
Annex A5 for Test Method E
NOTE 1—Alternative apparatus may be used, such as the U-tube method for dark oils, provided it has been shown to give results of the same precision
and accuracy as those described in the annexes.
6.2 Heating and Cooling Bath—A suitable air bath, a nonvolatile, transparent liquid bath, or an infrared lamp (250 W to 375 W),
provided with means for controlling the rate of heating.
NOTE 2—Water should not be used as either a heating or cooling medium since aniline is hygroscopic and moist aniline will give erroneous test results.
For example, the aniline point of the n-heptane reagent as measured with aniline containing 0.1 % by volume water is approximately 0.5 °C (0.9 °F)
higher than that measured with dry aniline. If the aniline point is below the dew point of the atmosphere, pass a slow stream of dry inert gas into the
aniline point tube to blanket the aniline-sample mixture.
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.
D611 − 23
6.3 Thermometers, or other temperature sensing devices, such as thermocouples or platinum resistance thermometers that cover
the temperamental range of interest and can provide equivalent or better accuracy and precision, may be used in place of the
thermometers having the following ranges and conforming to the requirements of the designated ASTM or IP specification:
ASTM
Range IP
(Specification E1)
−38 °C to + 42 °C (−36.5 °F 33C, 33F 20C
to + 107.5 °F)
25 °C to 105 °C (77 °F to 221 °F) 34C, 34F 21C
90 °C to 170 °C (194 °F to 338 °F) 35C, 35F 59C
6.4 Pipets, or equivalent volume dispensing devices, capable of delivering volumes with capacities of 10 mL 6 0.04 mL and 5 mL
6 0.02 mL, for use in the test.
6.5 Balance—A laboratory balance sensitive to 0.01 g, suitable for weighing the tube and sample when the sample cannot be
pipetted conveniently.
6.6 Safety Goggles.
6.7 Plastic Gloves, impervious to aniline.
7. Reagents
7.1 Aniline (Warning—Aniline should not be pipetted directly by mouth because of its extreme toxicity. Aniline is also toxic by
absorption through the skin even in very small quantities, and should be handled with great caution.) The aniline shall be
sufficiently pure such that when tested with n-heptane according to Section 9, it shall give an aniline point of 69.3 °C 6 0.2 °C
(156.7 °F 6 0.4 °F) as determined from the average of two independent tests having a difference of not more than 0.1 °C (0.2 °F).
If the aniline point of heptane is higher than this specification, the aniline may be dried by distillation, where the first and last 10 %
are discarded. If the aniline point is lower, water may be added until the aniline meets the specification.
NOTE 3—It is estimated that approximately 400 ppm to 1400 ppm of water in aniline is required to meet the heptane specification.
NOTE 4—As an alternative to distilling the aniline on the day of use, the aniline may be distilled as described in 7.1, collecting the distillate in ampoules,
sealing the ampoules under vacuum or dry nitrogen, and storing in a cool dark place for future use. Alternatively, distillate may be stored under dry
nitrogen in a glass bottle or in single use ampoules kept in a cool, dark place. In either case, rigid precaution must be taken to avoid contamination from
atmospheric moisture (Note 2). It is believed that under these conditions the aniline will remain unchanged for a period exceeding 6 months.
7.2 Calcium Sulfate, anhydrous.
7.3 n-Heptane, spectroscopic or HPLC grade. (Warning—Flammable. Harmful if inhaled. Keep away from heat, sparks, and open
flame. Keep container closed. Use with adequate ventilation. Avoid prolonged breathing of vapor or spray mist. Avoid prolonged
or repeated skin contact.)
8. Sample
8.1 Dry the sample by shaking vigorously for 3 min to 5 min with about 10 % by volume of a suitable drying agent such as
anhydrous calcium sulfate or anhydrous sodium sulfate. Reduce the viscosity of viscous samples by warming to a temperature
below that which would cause the loss of light ends or the dehydration of the drying agent. Remove any suspended drying agent
by use of a centrifuge or by filtration. Heat samples containing separated wax until they are homogeneous and keep heated during
filtration or centrifugation to ensure against separation of wax. When suspended water is visibly present and the sample material
is known to dissolve less than 0.03 % by mass of water, the use of a centrifuge for the removal of suspended water is an acceptable
procedure.
9. Procedure for Aniline Point
9.1 The following methods, to be used as applicable, are covered as follows:
D611 − 23
9.1.1 Test Method A, described in detail in Annex A1, is applicable to clear samples or to samples not darker than No. 6.5 ASTM
color, as determined by Test Method D1500, having initial boiling points well above the expected aniline point.
9.1.2 Test Method B, described in detail in Annex A2, is applicable to light-colored samples, moderately dark samples, and to very
dark samples. It is suitable for samples that are too dark to be tested by Test Method A.
9.1.3 Test Method C, described in detail in Annex A3, is applicable to clear samples or to samples not darker than No. 6.5 ASTM
color, as determined by Test Method D1500, having initial boiling points sufficiently low as to give incorrect aniline point readings
by Test Method A, for example, aviation gasoline.
9.1.4 Test Method D, described in detail in Annex A4, is applicable to the same type of sample as Test Method C. It is particularly
useful when only limited quantities of sample are available.
9.1.5 Test Method E is applicable when using automatic apparatus in accordance with the instructions in Annex A5.
10. Procedure for Mixed Aniline Point
10.1 This procedure is applicable to samples having aniline points below the temperature at which aniline crystallizes from the
mixture. Deliver 10 mL of aniline (Warning—See 7.1), 5 mL of sample, and 5 mL of n-heptane into a clean, dry apparatus.
Determine the aniline point of the mixture by Test Method A or B as described in Annex A1 or Annex A2.
11. Report
11.1 If the range of three successive observations of the aniline point temperature is not greater than 0.1 °C (0.2 °F) for
light-colored samples or 0.2 °C (0.4 °F) for dark samples, report the average temperature of these observations, corrected for
thermometer calibration errors, to the nearest 0.05 °C (0.1 °F) as the aniline point.
11.2 If such a range is not obtained after five observations, repeat the test using fresh quantities of aniline and sample in a clean,
dry apparatus, and if consecutive temperature observations show a progressive change, or if the range of observations is greater
than the repeatability given in 12.1, report the test method as being inapplicable.
12. Precision and Bias
12.1 The precision of these test methods as obtained by statistical examination of interlaboratory test results is as follows:
12.1.1 Repeatability—The difference between successive
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