ASTM D974-04
(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
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 109; extremely weak acids or bases whose dissociation constants are smaller than 109 do not interfere. Salts react if their hydrolysis constants are larger than 109.
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 D 4739 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 D 664. The acid numbers obtained by this color-indicator test method need not be numerically the same as those obtained by Test Method D 664, the base numbers obtained by this color indicator test method need not be numerically the same as those obtained by Test Method D 4739, but they are generally of the same order of magnitude.
1.3 The values stated in acceptable SI units are to be regarded as the 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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An American National Standard
Designation:D974–04
Designation: 139/98
Standard Test Method for
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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 (e) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
numerically the same as those obtained by Test Method D664, the base
1. Scope*
numbers obtained by this color indicator test method need not be
1.1 This test method covers the determination of acidic or
numerically the same as those obtained by Test Method D4739, but they
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basic constituents (Note 1) in petroleum products and lubri-
are generally of the same order of magnitude.
cants soluble or nearly soluble in mixtures of toluene and
1.3 The values stated in acceptable SI units are to be
isopropylalcohol.Itisapplicableforthedeterminationofacids
regarded as the standard.
or bases whose dissociation constants in water are larger than
1.4 This standard does not purport to address all of the
−9
10 ; extremely weak acids or bases whose dissociation
safety concerns, if any, associated with its use. It is the
−9
constants are smaller than 10 do not interfere. Salts react if
responsibility of the user of this standard to establish appro-
−9
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
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2.1 ASTM Standards:
have basic properties include organic and inorganic bases, amino com-
D117 Guide for Sampling, Test Methods, Specifications,
pounds, salts of weak acids (soaps), basic salts of polyacidic bases, salts
and Guide for Electrical Insulating Oils of Petroleum
of heavy metals, and addition agents such as inhibitors and detergents.
Origin
NOTE 2—This test method is not suitable for measuring the basic
D664 TestMethodforAcidNumberofPetroleumProducts
constituents of many basic additive-type lubricating oils. Test Method
by Potentiometric Titration
D4739 can be used for this purpose.
D1193 Specification for Reagent Water
1.2 Thistestmethodcanbeusedtoindicaterelativechanges
D4175 Terminology Relating to Petroleum, Petroleum
that occur in an oil during use under oxidizing conditions.
Products, and Lubricants
Although the titration is made under definite equilibrium
D4739 Test Method for Base Number Determination by
conditions, the method does not measure an absolute acidic or
Potentiometric Titration
basicpropertythatcanbeusedtopredictperformanceofanoil
3. Terminology
under service conditions. No general relationship between
bearing corrosion and acid or base numbers is known. 3.1 Definitions:
3.1.1 acid number, n—the quantity of base, expressed in
NOTE 3—Oils, such as many cutting oils, rustproofing oils, and similar
milligrams of potassium hydroxide per gram of sample that is
compounded oils, or excessively dark-colored oils, that cannot be ana-
required to titrate a sample to a specified end point.
lyzed for acid number by this test method due to obscurity of the
color-indicatorendpoint,canbeanalyzedbyTestMethodD664.Theacid 3.1.1.1 Discussion—In this test method, the indicator is
numbers obtained by this color-indicator test method need not be
p-naphtholbenzeintitratedtoagreen/green-brownendpointin
a toluene-water-isopropanol solvent.
3.1.2 base number, n—the quantity of acid, expressed in
1
milligrams of potassium hydroxide per gram of sample that is
This test method is under the jurisdiction of ASTM Committee D02 on
PetroleumProductsandLubricantsandisthedirectresponsibilityofSubcommittee
required to titrate a sample to a specified end point.
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.
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Current edition approved Nov. 1, 2004. Published November 2004. Originally For referenced ASTM standards, visit the ASTM website, www.astm.org, or
e1
approve in 1948. Last previous edition approved in 2002 as D974–02 . contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
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Statementsdefiningthistestmethod,itsmodification,anditssignificancewhen Standards volume information, refer to the standard’s Document Summary page on
applied to
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