ASTM D4739-23
(Test Method)Standard Test Method for Base Number Determination by Potentiometric Hydrochloric Acid Titration
Standard Test Method for Base Number Determination by Potentiometric Hydrochloric Acid Titration
SIGNIFICANCE AND USE
5.1 New and used petroleum products can contain basic constituents that are present as additives. The relative amount of these materials can be determined by titration with acids. The base number is a measure of the amount of basic substances in the oil always under the conditions of the test. It is sometimes used as a measure of lubricant degradation in service. However, any condemning limit shall be empirically established.
5.2 As stated in 1.2, this test method uses a weaker acid to titrate the base than Test Method D2896, and the titration solvents are also different. Test Method D2896 uses a stronger acid and a more polar solvent system than Test Method D4739. As a result, Test Method D2896 will titrate salts of weak acids (soaps), basic salts of polyacidic bases, and weak alkaline salts of some metals. They do not protect the oil from acidic components due to the degradation of the oil. This test method may produce a falsely exaggerated base number. Test Method D4739 will probably not titrate these weak bases but, if so, will titrate them to a lesser degree of completion. It measures only the basic components of the additive package that neutralizes acids. On the other hand, if the additive package contains weak basic components that do not play a role in neutralizing the acidic components of the degrading oil, then the Test Method D4739 result may be falsely understated.
5.3 Particular care is required in the interpretation of the base number of new and used lubricants.
5.3.1 When the base number of the new oil is required as an expression of its manufactured quality, Test Method D2896 is preferred, since it is known to titrate weak bases that this test method may or may not titrate reliably.
5.3.2 When the base number of in-service or at-term oil is required, this test method is preferred because in many cases, especially for internal combustion engine oils, weakly basic degradation products are possible. Test Method D2896 will titrate these, thu...
SCOPE
1.1 This test method covers a procedure for the determination of basic constituents in petroleum products and new and used lubricants. This test method resolves these constituents into groups having weak-base and strong-base ionization properties, provided the dissociation constants of the more strongly basic compounds are at least 1000 times than that of the next weaker groups. This test method covers base numbers up to 250.
1.2 In new and used lubricants, the constituents that can be considered to have basic properties are primarily organic and inorganic bases, including amino compounds. This test method uses hydrochloric acid as the titrant, whereas Test Method D2896 uses perchloric acid as the titrant. This test method may or may not titrate these weak bases and, if so, it will titrate them to a lesser degree of completion; some additives such as inhibitors or detergents may show basic characteristics.
1.3 When testing used engine lubricants, it should be recognized that certain weak bases are the result of the service rather than having been built into the oil. This test method can be used to indicate relative changes that occur in oil during use under oxidizing or other service conditions regardless of the color or other properties of the resulting oil. The values obtained, however, are intended to be compared with the other values obtained by this test method only; base numbers obtained by this test method are not intended to be equal to values by other test methods. Although the analysis is made under closely specified conditions, this test method is not intended to, and does not, result in reported basic properties that can be used under all service conditions to predict performance of an oil; for example, no overall relationship is known between bearing corrosion or the control of corrosive wear in the engine and base number.
1.4 This test method was developed as an alternative for the former base numb...
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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: D4739 − 23
Standard Test Method for
Base Number Determination by Potentiometric Hydrochloric
1
Acid Titration
This standard is issued under the fixed designation D4739; 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.
INTRODUCTION
Currently, there are two ASTM test methods under the jurisdiction of Committee D02 used for
determining base number by potentiometric titration: Test Method D2896 and Test Method D4739.
They are both used throughout the petroleum industry. Test Method D2896 is for new oils and is used
in setting specifications since it is more accurate than Test Method D4739. Test Method D4739 shall
be used exclusively for the purpose of tracking base number loss as an oil proceeds in service. In many
cases, the test methods will provide different results. Some comparisons are given in the Scope and
the Significance and Use sections of this test method to distinguish between the two standards and to
provide guidance to users.
1. Scope* values obtained by this test method only; base numbers
obtained by this test method are not intended to be equal to
1.1 This test method covers a procedure for the determina-
values by other test methods. Although the analysis is made
tion of basic constituents in petroleum products and new and
under closely specified conditions, this test method is not
used lubricants. This test method resolves these constituents
intended to, and does not, result in reported basic properties
into groups having weak-base and strong-base ionization
that can be used under all service conditions to predict
properties, provided the dissociation constants of the more
performance of an oil; for example, no overall relationship is
strongly basic compounds are at least 1000 times than that of
known between bearing corrosion or the control of corrosive
the next weaker groups. This test method covers base numbers
wear in the engine and base number.
up to 250.
1.4 This test method was developed as an alternative for the
1.2 In new and used lubricants, the constituents that can be
former base number portion of Test Method D664 (last
considered to have basic properties are primarily organic and
published in Test Method D664 – 81).
inorganic bases, including amino compounds. This test method
1.4.1 Colorimetric test methods for base number are Test
uses hydrochloric acid as the titrant, whereas Test Method
Method D974, IP 139, and 5102.1 on acid and base number by
D2896 uses perchloric acid as the titrant. This test method may
extraction (color-indicator titration) of Federal Test Method
or may not titrate these weak bases and, if so, it will titrate
Standard No. 791b. Test results by these methods may or may
them to a lesser degree of completion; some additives such as
not be numerically equivalent to this test method.
inhibitors or detergents may show basic characteristics.
1.5 The values stated in SI units are to be regarded as
1.3 When testing used engine lubricants, it should be
standard. No other units of measurement are included in this
recognized that certain weak bases are the result of the service
standard.
rather than having been built into the oil. This test method can
1.6 This standard does not purport to address all of the
be used to indicate relative changes that occur in oil during use
under oxidizing or other service conditions regardless of the safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
color or other properties of the resulting oil. The values
obtained, however, are intended to be compared with the other priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
1.7 This international standard was developed in accor-
1
dance with internationally recognized principles on standard-
This test method is under the jurisdiction of ASTM Committee D02 on
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of
ization established in the Decision on Principles for the
Subcommittee D02.06 on Analysis of Liquid Fuels and Lubricants.
Development of International Standards, Guides and Recom-
Current edition approved July 1, 2023. Published August 2023. Originally
mendations issued by the World Trade Organization Technical
approved in 1987. Last previous edition approved in 2017 as D4739 – 17. DOI:
10.1520/D4739-23. Barriers to Trade (TBT) Committee
...
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: D4739 − 17 D4739 − 23
Standard Test Method for
Base Number Determination by Potentiometric Hydrochloric
1
Acid Titration
This standard is issued under the fixed designation D4739; 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.
INTRODUCTION
Currently, there are two ASTM test methods under the jurisdiction of Committee D02 used for
determining base number by potentiometric titration: Test Method D2896 and Test Method D4739.
They are both used throughout the petroleum industry. Test Method D2896 is for new oils and is used
in setting specifications since it is more accurate than Test Method D4739. Test Method D4739 shall
be used exclusively for the purpose of tracking base number loss as an oil proceeds in service. In many
cases, the test methods will provide different results. Some comparisons are given in the Scope and
the Significance and Use sections of this test method to distinguish between the two standards and to
provide guidance to users.
1. Scope*
1.1 This test method covers a procedure for the determination of basic constituents in petroleum products and new and used
lubricants. This test method resolves these constituents into groups having weak-base and strong-base ionization properties,
provided the dissociation constants of the more strongly basic compounds are at least 1000 times than that of the next weaker
groups. This test method covers base numbers up to 250.
1.2 In new and used lubricants, the constituents that can be considered to have basic properties are primarily organic and inorganic
bases, including amino compounds. This test method uses hydrochloric acid as the titrant, whereas Test Method D2896 uses
perchloric acid as the titrant. This test method may or may not titrate these weak bases and, if so, it will titrate them to a lesser
degree of completion; some additives such as inhibitors or detergents may show basic characteristics.
1.3 When testing used engine lubricants, it should be recognized that certain weak bases are the result of the service rather than
having been built into the oil. This test method can be used to indicate relative changes that occur in oil during use under oxidizing
or other service conditions regardless of the color or other properties of the resulting oil. The values obtained, however, are
intended to be compared with the other values obtained by this test method only; base numbers obtained by this test method are
not intended to be equal to values by other test methods. Although the analysis is made under closely specified conditions, this
test method is not intended to, and does not, result in reported basic properties that can be used under all service conditions to
predict performance of an oil; for example, no overall relationship is known between bearing corrosion or the control of corrosive
wear in the engine and base number.
1.4 This test method was developed as an alternative for the former base number portion of Test Method D664 (last published in
Test Method D664 – 81).
1
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
D02.06 on Analysis of Liquid Fuels and Lubricants.
Current edition approved Dec. 1, 2017July 1, 2023. Published February 2018August 2023. Originally approved in 1987. Last previous edition approved in 2017 as
D4739 – 11 (2017).D4739 – 17. DOI: 10.1520/D4739-17.10.1520/D4739-23.
*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
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D4739 − 23
1.4.1 Colorimetric test methods for base number are Test Method D974, IP 139, and 5102.1 on acid and base number by extraction
(color-indicator titration) of Federal Test Method Standard No. 791b. Test results by these methods may or may not be numerically
equivalent to this test method.
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.6 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 saf
...
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