ASTM D974-12
(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
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 oilalways 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.
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 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 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 and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: D974 − 12
Designation:139/98
Standard Test Method for
1
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.
numbers obtained by this color indicator test method need not be
1. Scope*
numerically the same as those obtained by Test Method D4739, but they
1.1 This test method covers the determination of acidic or
are generally of the same order of magnitude.
2
basic constituents (Note 1) in petroleum products and lubri-
1.3 The values stated in SI units are to be regarded as
cants soluble or nearly soluble in mixtures of toluene and
standard. No other units of measurement are included in this
isopropylalcohol.Itisapplicableforthedeterminationofacids
standard.
or bases whose dissociation constants in water are larger than
−9
1.4 This standard does not purport to address all of the
10 ; extremely weak acids or bases whose dissociation
−9
safety concerns, if any, associated with its use. It is the
constants are smaller than 10 do not interfere. Salts react if
−9
responsibility of the user of this standard to establish appro-
their hydrolysis constants are larger than 10 .
priate safety and health practices and determine the applica-
NOTE 1—In new and used oils, the constituents considered to have
bility of regulatory limitations prior to use.
acidic characteristics include organic and inorganic acids, esters, phenolic
compounds, lactones, resins, salts of heavy metals, and addition agents
2. Referenced Documents
such as inhibitors and detergents. Similarly, constituents considered to
3
have basic properties include organic and inorganic bases, amino
2.1 ASTM Standards:
compounds, salts of weak acids (soaps), basic salts of polyacidic bases,
D117Guide for Sampling, Test Methods, and Specifications
salts of heavy metals, and addition agents such as inhibitors and
for Electrical Insulating Oils of Petroleum Origin
detergents.
D664Test Method for Acid Number of Petroleum Products
NOTE 2—This test method is not suitable for measuring the basic
by Potentiometric Titration
constituents of many basic additive-type lubricating oils. Test Method
D4739 can be used for this purpose.
D1193Specification for Reagent Water
D4175 Terminology Relating to Petroleum, Petroleum
1.2 Thistestmethodcanbeusedtoindicaterelativechanges
Products, and Lubricants
that occur in an oil during use under oxidizing conditions.
D4739Test Method for Base Number Determination by
Although the titration is made under definite equilibrium
Potentiometric Hydrochloric Acid Titration
conditions, the method does not measure an absolute acidic or
basicpropertythatcanbeusedtopredictperformanceofanoil
3. Terminology
under service conditions. No general relationship between
3.1 Definitions:
bearing corrosion and acid or base numbers is known.
3.1.1 acid number, n—the quantity of a specified base,
NOTE 3—Oils, such as many cutting oils, rustproofing oils, and similar
expressed in milligrams of potassium hydroxide per gram of
compounded oils, or excessively dark-colored oils, that cannot be ana-
sample, required to titrate a sample in a specified solvent to a
lyzed for acid number by this test method due to obscurity of the
color-indicatorendpoint,canbeanalyzedbyTestMethodD664.Theacid specified endpoint using a specified detection system.
numbers obtained by this color-indicator test method need not be
3.1.1.1 Discussion—In this test method, the indicator is
numerically the same as those obtained by Test Method D664, the base
p-naphtholbenzeintitratedtoagreen/green-brownendpointin
a toluene-water-isopropanol solvent.
1
This test method is under the jurisdiction of ASTM Committee D02 on
3.1.2 base number, n—the quantity of a specified acid,
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of
expressed in terms of the equivalent number of milligrams of
Subcommittee D02.06 on Analysis of Lubricants.
potassium hydroxide per gram of sample, required to titrate a
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 April 15, 2012. Published June 2012. Originally
3
approved in 1948. Last previous edition approved in 2011 as D974–11. DOI: For referenced ASTM standards, visit the ASTM website, www.astm.org, or
10.1520/D0974-12. contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
2
Statementsdefinin
...
This document is not anASTM standard and is intended only to provide the user of anASTM 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:D974–11 Designation:D974–12
Designation: 139/98
Standard Test Method for
1
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 Department of Defense.
1. Scope*
2
1.1 This test method covers the determination of acidic or basic constituents (Note 1) in petroleum products and lubricants
solubleornearlysolubleinmixturesoftolueneandisopropylalcohol.Itisapplicableforthedeterminationofacidsorbaseswhose
−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 byTest 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 and health practices and determine the applicability of regulatory
limitations prior to use.
2. Referenced Documents
3
2.1 ASTM Standards:
D117 Guide for Sampling, Test Methods, and Specifications for Electrical Insulating Oils of Petroleum Origin
D664 Test Method for Acid Number of Petroleum Products by Potentiometric Titration
D1193 Specification for Reagent Water
D4175 Terminology Relating to Petroleum, Petroleum Products, and Lubricants
D4739 Test Method for Base Number Determination by Potentiometric Hydrochloric Acid Titration
1
This test method is under the jurisdiction ofASTM Committee D02 on Petroleum Products and Lubricants and is the direct responsibility of Subcommittee D02.06 on
Analysis of Lubricants.
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.
´1
Current edition approved May 15, 2011. Published July 2011. Originally approved in 1948. Last previous edition approved in 2008 as D974–08 . DOI:
10.1520/D0974-11.
CurrenteditionapprovedApril15,2012.PublishedJune2012.Originallyapprovedin1948.Lastpreviouseditionapprovedin2011asD974–11.DOI:10.1520/D0974-12.
2
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.
3
ForreferencedASTMstandards,visittheASTMwebsite,www.astm.org,orcontactASTMCustomerServiceatservice@astm.org.For Annual Book of ASTM Standards
volume inform
...
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