ASTM D4739-96
(Test Method)Standard Test Method for Base Number Determination by Potentiometric Titration
Standard Test Method for Base Number Determination by Potentiometric Titration
SCOPE
1.1 This test method covers a procedure for the determination of basic constituents in petroleum products and lubricants (Note 1). The test method resolves these constituents into groups having weak-base and strong-base ionization properties, provided the dissociation constants of the more strongly basic compounds are at least 1000 times that of the next weaker groups.
1.1.1 This test method covers base numbers up to 70. While it can be extended to higher base numbers, the precision of the test method for base numbers greater than 70 has not been determined.
Note 1-In new and used oils, the constituents which can be considered to have basic properties are primarily organic and inorganic bases, including amino compounds, although certain salts of heavy metals, salts of weak acids, basic salts of polyacidic compounds, and some additives such as inhibitors or detergents may show basic characteristics.
1.2 This test method can be used to indicate relative changes that occur in an oil during use under oxidizing or other service conditions regardless of the color or other properties of the resulting oil (Note 2). Although the analysis is made under closely specified conditions, the method is not intended to, and does not, result in reported basic properties which can be used under all service conditions to predict performance of an oil; for example, no overall relationship is known between bearing corrosion or the control of corrosive wear in the engine and base number.
Note 2-A color indicator titration method is also available in the Test Method D 974 and IP139. The base numbers obtained by the potentiometric method may or may not be numerically the same as those obtained by Test Method D 974 or equivalent color indicator methods such as given in Federal Test Method Std. No. 791b. Potentiometric methods for base number are also available in Test Method D 2896.
Note 3-Test Method D 4739 was developed as an alternative for the former base number portion of Test Method D 664. Base numbers obtained by this method may or may not be numerically the same as those obtained by the former base number portion of Test Method D 664.
1.3 The values stated in acceptable metric 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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Designation: D 4739 – 96 An American National Standard
AMERICAN SOCIETY FOR TESTING AND MATERIALS
100 Barr Harbor Dr., West Conshohocken, PA 19428
Reprinted from the Annual Book of ASTM Standards. Copyright ASTM
Standard Test Method for
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Base Number Determination by Potentiometric Titration
This standard is issued under the fixed designation D 4739; 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.
1. Scope 1.4 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
1.1 This test method covers a procedure for the determina-
responsibility of the user of this standard to establish appro-
tion of basic constituents in petroleum products and lubricants
priate safety and health practices and determine the applica-
(Note 1). The test method resolves these constituents into
bility of regulatory limitations prior to use.
groups having weak-base and strong-base ionization proper-
ties, provided the dissociation constants of the more strongly
2. Referenced Documents
basic compounds are at least 1000 times that of the next weaker
2.1 ASTM Standards:
groups.
D 664 Test Method for Acid Number of Petroleum Products
1.1.1 This test method covers base numbers up to 70. While
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by Potentiometric Titration
it can be extended to higher base numbers, the precision of the
D 974 Test Method for Acid and Base Number by Color-
test method for base numbers greater than 70 has not been
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Indicator Titration
determined.
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D 1193 Specification for Reagent Water
NOTE 1—In new and used oils, the constituents which can be consid- D 2896 Test Method for Base Number of Petroleum Prod-
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ered to have basic properties are primarily organic and inorganic bases,
ucts by Potentiometric Perchloric Acid Titration
including amino compounds, although certain salts of heavy metals, salts
2.2 IP Standard:
of weak acids, basic salts of polyacidic compounds, and some additives
IP 139 Test Method for Neutralization Number by Color-
such as inhibitors or detergents may show basic characteristics.
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Indicator Titration
1.2 This test method can be used to indicate relative changes
2.3 U.S. Federal Test Method:
that occur in an oil during use under oxidizing or other service
Federal Test Method Standard No. 791b Lubricants Liquid
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conditions regardless of the color or other properties of the
Fuels and Related Products; Methods of Testing
resulting oil (Note 2). Although the analysis is made under
3. Terminology
closely specified conditions, the method is not intended to, and
3.1 Definitions:
does not, result in reported basic properties which can be used
3.1.1 base numbers, n—the quantity of acid, expressed in
under all service conditions to predict performance of an oil;
milligrams of potassium hydroxide per gram of sample that is
for example, no overall relationship is known between bearing
required to titrate a sample to a specified end point.
corrosion or the control of corrosive wear in the engine and
3.1.1.1 Discussion— In this test method, the sample is
base number.
titrated to a meter reading corresponding to a freshly prepared
NOTE 2—A color indicator titration method is also available in the Test
nonaqueous acidic buffer solution.
Method D 974 and IP 139. The base numbers obtained by the potentio-
3.2 Definitions of Terms Specific to This Standard:
metric method may or may not be numerically the same as those obtained
3.2.1 strong base number, n—the quantity of acid, ex-
by Test Method D 974 or equivalent color indicator methods such as given
in Federal Test Method Std. No. 791b. Potentiometric methods for base pressed in terms of the equivalent number of milligrams of
number are also available in Test Method D 2896.
potassium hydroxide per gram of sample, that is required to
NOTE 3—Test Method D 4739 was developed as an alternative for the
titrate a sample dissolved in the specified solvent from the
former base number portion of Test Method D 664. Base numbers
initial meter reading to a meter reading corresponding to a
obtained by this method may or may not be numerically the same as those
freshly prepared basic buffer solution.
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obtained by the former base number portion of Test Method D 664.
4. Summary of Test Method
1.3 The values stated in acceptable metric units are to be
regarded as the standard. 4.1 The sample is dissolved in a mixture of toluene,
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Annual Book of ASTM Standards, Vol 05.01.
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This test method is under the jurisdiction of ASTM Committee D-2 on Annual Book of ASTM Standards, Vol 11.01.
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Petroleum Products and Lubricants and is the direct responsibility of Subc
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