ASTM D974-02
(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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Standards Content (Sample)
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An American National Standard
Designation: D 974 – 02
British Standard 2634
Designation: 139/98
Standard Test Method for
1,2
Acid and Base Number by Color-Indicator Titration
This standard is issued under the fixed designation D 974; 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 (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.
numbers obtained by this color-indicator test method need not be
1. Scope *
numerically the same as those obtained by Test Method D 664, the base
1.1 This test method covers the determination of acidic or
numbers obtained by this color indicator test method need not be
3
basic constituents (Note 1) in petroleum products and lubri-
numerically the same as those obtained by Test Method D 4739, but they
cants soluble or nearly soluble in mixtures of toluene and
are generally of the same order of magnitude.
isopropyl alcohol. It is applicable for the determination of acids
1.3 The values stated in acceptable SI units are to be
or bases whose dissociation constants in water are larger than
regarded as the standard.
−9
10 ; extremely weak acids or bases whose dissociation
1.4 This standard does not purport to address all of the
−9
constants are smaller than 10 do not interfere. Salts react if
safety concerns, if any, associated with its use. It is the
−9
their hydrolysis constants are larger than 10 .
responsibility of the user of this standard to establish appro-
NOTE 1—In new and used oils, the constituents considered to have priate safety and health practices and determine the applica-
acidic characteristics include organic and inorganic acids, esters, phenolic
bility of regulatory limitations prior to use.
compounds, lactones, resins, salts of heavy metals, and addition agents
such as inhibitors and detergents. Similarly, constituents considered to
2. Referenced Documents
have basic properties include organic and inorganic bases, amino com-
2.1 ASTM Standards:
pounds, salts of weak acids (soaps), basic salts of polyacidic bases, salts
D 117 Guide for Sampling, Test Methods, Specifications,
of heavy metals, and addition agents such as inhibitors and detergents.
and Guide for Electrical Insulating Oils of Petroleum
4
NOTE 2—This test method is not suitable for measuring the basic Origin
constituents of many basic additive-type lubricating oils. Test Method
D 664 Test Method for Acid Number of Petroleum Products
5
D 4739 can be used for this purpose.
by Potentiometric Titration
6
D 1193 Specification for Reagent Water
1.2 This test method can be used to indicate relative changes
that occur in an oil during use under oxidizing conditions. D 4175 Terminology Relating to Petroleum, Petroleum
7
Products, and Lubricants
Although the titration is made under definite equilibrium
conditions, the method does not measure an absolute acidic or D 4739 Test Method for Base Number Determination by
7
Potentiometric Titration
basic property that can be used to predict performance of an oil
under service conditions. No general relationship between
3. Terminology
bearing corrosion and acid or base numbers is known.
3.1 Definitions:
NOTE 3—Oils, such as many cutting oils, rustproofing oils, and similar
3.1.1 acid number, n—the quantity of base, expressed in
compounded oils, or excessively dark-colored oils, that cannot be ana-
milligrams of potassium hydroxide per gram of sample that is
lyzed for acid number by this test method due to obscurity of the
required to titrate a sample to a specified end point.
color-indicator end point, can be analyzed by Test Method D 664. The acid
3.1.1.1 Discussion—In this test method, the indicator is
p-naptholbenzein titrated to a green/green-brown end point in
1
This test method is under the jurisdiction of ASTM Committee D02 on
a toluene-water-isopropanol solvent.
Petroleum Products and Lubricants and is the direct responsibility of Subcommittee
3.1.2 base number, n—the quantity of acid, expressed in
D02.06 on Analysis of Lubricants.
milligrams of potassium hydroxide per gram of sample that is
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.
required to titrate a sample to a specified end point.
Current edition approved June 10, 2002. Published August 2002. Originally
published as D 974–48T. Last previous edition D 974–01.
2 4
This test method has been adopted for use by government agencies to replace Annual Book of ASTM Standards, Vol 10.03.
5
Method 5105 of Federal Test Method Standard No. 791b. Annual Book of ASTM Standards,
...
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