ASTM D974-22
(Test Method)Standard Test Method for Acid and Base Number by Color-Indicator Titration
Standard Test Method for Acid and Base Number by Color-Indicator Titration
SIGNIFICANCE AND USE
5.1 New and used petroleum products can contain basic or acidic constituents that are present as additives or as degradation products formed during service, such as oxidation products. The relative amount of these materials can be determined by titrating with acids or bases. This number, whether expressed as acid number or base number, is a measure of this amount of acidic or basic substances, respectively, in the oil—always under the conditions of the test. This number is used as a guide in the quality control of lubricating oil formulations. It is also sometimes used as a measure of lubricant degradation in service; however, any condemning limits must be empirically established.
5.2 Since a variety of oxidation products contribute to the acid number and the organic acids vary widely in corrosive properties, the test cannot be used to predict corrosiveness of an oil under service conditions. No general correlation is known between acid number and the corrosive tendency of oils toward metals. Compounded engine oils can and usually do have both acid and base numbers in this test method.
SCOPE
1.1 This test method covers the determination of acidic or basic constituents (Note 1) in petroleum products3 and lubricants soluble or nearly soluble in mixtures of toluene and isopropyl alcohol. It is applicable for the determination of acids or bases whose dissociation constants in water are larger than 10−9; extremely weak acids or bases whose dissociation constants are smaller than 10−9 do not interfere. Salts react if their hydrolysis constants are larger than 10−9.
Note 1: In new and used oils, the constituents considered to have acidic characteristics include organic and inorganic acids, esters, phenolic compounds, lactones, resins, salts of heavy metals, and addition agents such as inhibitors and detergents. Similarly, constituents considered to have basic properties include organic and inorganic bases, amino compounds, salts of weak acids (soaps), basic salts of polyacidic bases, salts of heavy metals, and addition agents such as inhibitors and detergents.
Note 2: This test method is not suitable for measuring the basic constituents of many basic additive-type lubricating oils. Test Method D4739 can be used for this purpose.
1.2 This test method can be used to indicate relative changes that occur in an oil during use under oxidizing conditions. Although the titration is made under definite equilibrium conditions, the method does not measure an absolute acidic or basic property that can be used to predict performance of an oil under service conditions. No general relationship between bearing corrosion and acid or base numbers is known.
Note 3: Oils, such as many cutting oils, rustproofing oils, and similar compounded oils, or excessively dark-colored oils, that cannot be analyzed for acid number by this test method due to obscurity of the color-indicator end point, can be analyzed by Test Method D664. The acid numbers obtained by this color-indicator test method need not be numerically the same as those obtained by Test Method D664, the base numbers obtained by this color indicator test method need not be numerically the same as those obtained by Test Method D4739, but they are generally of the same order of magnitude.
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 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.
1.5 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...
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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: D974 − 22
Designation: 139/98 (2017)
Standard Test Method for
1,2
Acid and Base Number by Color-Indicator Titration
This standard is issued under the fixed designation D974; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber 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.
compounded oils, or excessively dark-colored oils, that cannot be ana-
1. Scope*
lyzed for acid number by this test method due to obscurity of the
1.1 This test method covers the determination of acidic or
color-indicatorendpoint,canbeanalyzedbyTestMethodD664.Theacid
3
basic constituents (Note 1) in petroleum products and lubri- numbers obtained by this color-indicator test method need not be
numerically the same as those obtained by Test Method D664, the base
cants soluble or nearly soluble in mixtures of toluene and
numbers obtained by this color indicator test method need not be
isopropylalcohol.Itisapplicableforthedeterminationofacids
numerically the same as those obtained by Test Method D4739, but they
or bases whose dissociation constants in water are larger than
are generally of the same order of magnitude.
−9
10 ; extremely weak acids or bases whose dissociation
−9 1.3 The values stated in SI units are to be regarded as
constants are smaller than 10 do not interfere. Salts react if
standard. No other units of measurement are included in this
−9
their hydrolysis constants are larger than 10 .
standard.
NOTE 1—In new and used oils, the constituents considered to have
1.4 This standard does not purport to address all of the
acidic characteristics include organic and inorganic acids, esters, phenolic
safety concerns, if any, associated with its use. It is the
compounds, lactones, resins, salts of heavy metals, and addition agents
responsibility of the user of this standard to establish appro-
such as inhibitors and detergents. Similarly, constituents considered to
have basic properties include organic and inorganic bases, amino
priate safety, health, and environmental practices and deter-
compounds, salts of weak acids (soaps), basic salts of polyacidic bases,
mine the applicability of regulatory limitations prior to use.
salts of heavy metals, and addition agents such as inhibitors and
1.5 This international standard was developed in accor-
detergents.
dance with internationally recognized principles on standard-
NOTE 2—This test method is not suitable for measuring the basic
constituents of many basic additive-type lubricating oils. Test Method ization established in the Decision on Principles for the
D4739 can be used for this purpose.
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
1.2 Thistestmethodcanbeusedtoindicaterelativechanges
Barriers to Trade (TBT) Committee.
that occur in an oil during use under oxidizing conditions.
Although the titration is made under definite equilibrium
2. Referenced Documents
conditions, the method does not measure an absolute acidic or
4
basicpropertythatcanbeusedtopredictperformanceofanoil
2.1 ASTM Standards:
under service conditions. No general relationship between
D117Guide for Sampling, Test Methods, and Specifications
bearing corrosion and acid or base numbers is known.
for Electrical Insulating Liquids
D664Test Method for Acid Number of Petroleum Products
NOTE 3—Oils, such as many cutting oils, rustproofing oils, and similar
by Potentiometric Titration
D1193Specification for Reagent Water
1
This test method is under the jurisdiction of ASTM International Committee
D4057Practice for Manual Sampling of Petroleum and
D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct
Petroleum Products
responsibility of ASTM Subcommittee D02.06 on Analysis of Liquid Fuels and
D4175Terminology Relating to Petroleum Products, Liquid
Lubricants. The technically equivalent standard as referenced is under the jurisdic-
tion of the Energy Institute Subcommittee SC-C-4.
Fuels, and Lubricants
Current edition approved Nov. 1, 2022. Published January 2023. Originally
D4177Practice for Automatic Sampling of Petroleum and
approved in 1948. Last previous edition approved in 2021 as D974–21. DOI:
Petroleum Products
10.1520/D0974-22.
This test method was adopted as a joint ASTM-IP standard in 1965.
2
This test method has been developed through the cooperative effort between
ASTMandtheEnergyInstitute,London.ASTMandIPstandardswereappr
...
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: D974 − 21 D974 − 22
Designation: 139/98 (2017)
Standard Test Method for
1,2
Acid and Base Number by Color-Indicator Titration
This standard is issued under the fixed designation D974; 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*
3
1.1 This test method covers the determination of acidic or basic constituents (Note 1) in petroleum products and lubricants soluble
or nearly soluble in mixtures of toluene and isopropyl alcohol. It is applicable for the determination of acids or bases whose
−9
dissociation constants in water are larger than 10 ; extremely weak acids or bases whose dissociation constants are smaller than
−9 −9
10 do not interfere. Salts react if their hydrolysis constants are larger than 10 .
NOTE 1—In new and used oils, the constituents considered to have acidic characteristics include organic and inorganic acids, esters, phenolic compounds,
lactones, resins, salts of heavy metals, and addition agents such as inhibitors and detergents. Similarly, constituents considered to have basic properties
include organic and inorganic bases, amino compounds, salts of weak acids (soaps), basic salts of polyacidic bases, salts of heavy metals, and addition
agents such as inhibitors and detergents.
NOTE 2—This test method is not suitable for measuring the basic constituents of many basic additive-type lubricating oils. Test Method D4739 can be
used for this purpose.
1.2 This test method can be used to indicate relative changes that occur in an oil during use under oxidizing conditions. Although
the titration is made under definite equilibrium conditions, the method does not measure an absolute acidic or basic property that
can be used to predict performance of an oil under service conditions. No general relationship between bearing corrosion and acid
or base numbers is known.
NOTE 3—Oils, such as many cutting oils, rustproofing oils, and similar compounded oils, or excessively dark-colored oils, that cannot be analyzed for
acid number by this test method due to obscurity of the color-indicator end point, can be analyzed by Test Method D664. The acid numbers obtained by
this color-indicator test method need not be numerically the same as those obtained by Test Method D664, the base numbers obtained by this color
indicator test method need not be numerically the same as those obtained by Test Method D4739, but they are generally of the same order of magnitude.
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
This test method is under the jurisdiction of ASTM International Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility
of ASTM Subcommittee D02.06 on Analysis of Liquid Fuels and Lubricants. The technically equivalent standard as referenced is under the jurisdiction of the Energy Institute
Subcommittee SC-C-4.
In the IP, this test method is under the jurisdiction of the Standardization Committee. This test method was adopted as a joint ASTM-IP standard in 1965.
Current edition approved July 1, 2021Nov. 1, 2022. Published July 2021January 2023. Originally approved in 1948. Last previous edition approved in 20142021 as
ɛ2
D974 – 14D974 – 21. . DOI: 10.1520/D0974-21.10.1520/D0974-22.
This test method was adopted as a joint ASTM-IP standard in 1965.
2
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.
3
Statements defining this test method, its modification, and its significance when applied to electrical insulating oils of mineral origin will be found in Guide D117.
*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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D974 − 22
1.4 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
...
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