ASTM D4739-02
(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 3). 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—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.
Note 3—A color indicator titration method is also available in the Test Method D 974 and IP 139. 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.
1.3 The values stated in 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:D4739–02
Standard Test Method for
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Base Number Determination by Potentiometric Titration
This standard is issued under the fixed designation D4739; 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.
1. Scope* 1.3 The values stated in SI units are to be regarded as the
standard.
1.1 This test method covers a procedure for the determina-
1.4 This standard does not purport to address all of the
tion of basic constituents in petroleum products and lubricants
safety concerns, if any, associated with its use. It is the
(Note 1). The test method resolves these constituents into
responsibility of the user of this standard to establish appro-
groups having weak-base and strong-base ionization proper-
priate safety and health practices and determine the applica-
ties, provided the dissociation constants of the more strongly
bility of regulatory limitations prior to use.
basiccompoundsareatleast1000timesthatofthenextweaker
groups.
2. Referenced Documents
1.1.1 Thistestmethodcoversbasenumbersupto70.While
2.1 ASTM Standards:
it can be extended to higher base numbers, the precision of the
D664 TestMethodforAcidNumberofPetroleumProducts
test method for base numbers greater than 70 has not been
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by Potentiometric Titration
determined.
D974 Test Method for Acid and Base Number by Color-
3
NOTE 1—In new and used oils, the constituents which can be consid-
Indicator Titration
ered to have basic properties are primarily organic and inorganic bases, 4
D1193 Specification for Reagent Water
including amino compounds, although certain salts of heavy metals, salts
D2896 Test Method for Base Number of Petroleum Prod-
of weak acids, basic salts of polyacidic compounds, and some additives
3
ucts by Potentiometric Perchloric Acid Titration
such as inhibitors or detergents may show basic characteristics.
2.2 IP Standard:
1.2 Thistestmethodcanbeusedtoindicaterelativechanges
IP139 Test Method for Acid Number by Color-Indicator
that occur in an oil during use under oxidizing or other service
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Titration Method
conditions regardless of the color or other properties of the
2.3 U.S. Federal Test Method:
resulting oil (Note 3). Although the analysis is made under
Federal Test Method Standard No. 791b Lubricants Liquid
closelyspecifiedconditions,themethodisnotintendedto,and
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Fuels and Related Products; Methods of Testing
does not, result in reported basic properties which can be used
under all service conditions to predict performance of an oil;
3. Terminology
for example, no overall relationship is known between bearing
3.1 Definitions:
corrosion or the control of corrosive wear in the engine and
3.1.1 base numbers, n—the quantity of acid, expressed in
base number.
milligrams of potassium hydroxide per gram of sample that is
NOTE 2—Test Method D4739 was developed as an alternative for the required to titrate a sample, dissolved in a specified solvent to
former base number portion of Test Method D664. Base numbers
a specified end point.
obtainedbythismethodmayormaynotbenumericallythesameasthose
3.1.1.1 Discussion—In this test method, the sample is
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obtained by the former base number portion of Test Method D664.
titrated to a meter reading corresponding to a freshly prepared
NOTE 3—Acolor indicator titration method is also available in theTest
nonaqueous acidic buffer solution.
Method D974 and IP139. 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-
byTestMethodD974orequivalentcolorindicatormethodssuchasgiven
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 D2896.
1 3
This test method is under the jurisdiction of ASTM Committee D02 on Annual Book of ASTM Standards, Vol 05.01.
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PetroleumProductsandLubricants andisthedirectresponsibilityofSubcommittee Annual Book of ASTM Standards, Vol 11.01.
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D02.06 on Analysis of Lubricants. IPStandards for Petroleum and Its Products, Part 1. Methods forAnalysis and
Current edition approved Dec. 10, 2002. Published February 2003. Originally Testing.
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approved in 1987. Last previous edition approve in 1996 as D4739–96. Available from Standardization Documents Order Desk, DODSSP, Bldg. 4,
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The base number portion was last published in the 1981 version. Section D, 700 Robbins Ave., Philadelphia, PA 19111-5098
*A Summary of Changes section appears at the end of this standard.
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