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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Publication Date
09-Jun-2002
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ASTM D974-02e1 - Standard Test Method for Acid and Base Number by Color-Indicator Titration
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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
An American National Standard
e1
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.
1
e NOTE—Corrected references in A2.5.1, A2.7.7, and A2.8.1 editorially in October 2003.
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-indicator end point, can be analyzed by Test Method D 664. The acid
3
basic constituents (Note 1) in petroleum products and lubri-
numbers obtained by this color-indicator test method need not be
cants soluble or nearly soluble in mixtures of toluene and
numerically the same as those obtained by Test Method D 664, the base
isopropyl alcohol. It is applicable for the determination of acids numbers obtained by this color indicator test method need not be
numerically the same as those obtained by Test Method D 4739, but they
or bases whose dissociation constants in water are larger than
−9
are generally of the same order of magnitude.
10 ; extremely weak acids or bases whose dissociation
−9
constants are smaller than 10 do not interfere. Salts react if
1.3 The values stated in acceptable SI units are to be
−9
their hydrolysis constants are larger than 10 . regarded as the standard.
1.4 This standard does not purport to address all of the
NOTE 1—In new and used oils, the constituents considered to have
safety concerns, if any, associated with its use. It is the
acidic characteristics include organic and inorganic acids, esters, phenolic
responsibility of the user of this standard to establish appro-
compounds, lactones, resins, salts of heavy metals, and addition agents
such as inhibitors and detergents. Similarly, constituents considered to priate safety and health practices and determine the applica-
have basic properties include organic and inorganic bases, amino com-
bility of regulatory limitations prior to use.
pounds, salts of weak acids (soaps), basic salts of polyacidic bases, salts
of heavy metals, and addition agents such as inhibitors and detergents.
2. Referenced Documents
2.1 ASTM Standards:
NOTE 2—This test method is not suitable for measuring the basic
D 117 Guide for Sampling, Test Methods, Specifications,
constituents of many basic additive-type lubricating oils. Test Method
and Guide for Electrical Insulating Oils of Petroleum
D 4739 can be used for this purpose.
4
Origin
1.2 This test method can be used to indicate relative changes
D 664 Test Method for Acid Number of Petroleum Products
that occur in an oil during use under oxidizing conditions.
5
by Potentiometric Titration
Although the titration is made under definite equilibrium
6
D 1193 Specification for Reagent Water
conditions, the method does not measure an absolute acidic or
D 4175 Terminology Relating to Petroleum, Petroleum
basic property that can be used to predict performance of an oil
7
Products, and Lubricants
under service conditions. No general relationship between
D 4739 Test Method for Base Number Determination by
bearing corrosion and acid or base numbers is known.
7
Potentiometric Titration
NOTE 3—Oils, such as many cutting oils, rustproofing oils, and similar
3. Terminology
3.1 Definitions:
1
This test method is under the jurisdiction of ASTM Committee D02 on
3.1.1 acid number, n—the quantity of base, expressed in
Petroleum Products and Lubricants and is the direct responsibility of Subcommittee
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
required to titrate a sample to a specified end point.
Committee. This test method was adopted as a joint ASTM-IP standard in 1965.
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, Vol 05.01.
3 6
Statements defining this test method, its modification, and its significance when Annual Book of ASTM Standards, Vol 11.01.
7
applied to electrical insulating oils of mineral origin will be found in Guide D 117. Annual Book of
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