ASTM D4739-08
(Test Method)Standard Test Method for Base Number Determination by Potentiometric Hydrochloric Acid Titration
Standard Test Method for Base Number Determination by Potentiometric Hydrochloric Acid Titration
SIGNIFICANCE AND USE
New and used petroleum products can contain basic constituents that are present as additives. The relative amount of these materials can be determined by titration with acids. The base number is a measure of the amount of basic substances in the oil always under the conditions of the test. It is sometimes used as a measure of lubricant degradation in service. However, any condemning limit shall be empirically established.
5.2 As stated in 1.2, this test method uses a weaker acid to titrate the base than Test Method D 2896, and the titration solvents are also different. Test Method D 2896 uses a stronger acid and a more polar solvent system than Test Method D 4739. As a result, Test Method D 2896 will titrate salts of weak acids (soaps), basic salts of polyacidic bases, and weak alkaline salts of some metals. They do not protect the oil from acidic components due to the degradation of the oil. This test method may produce a falsely exaggerated base number. Test Method D 4739 will probably not titrate these weak bases but, if so, will titrate them to a lesser degree of completion. It measures only the basic components of the additive package that neutralizes acids. On the other hand, if the additive package contains weak basic components that do not play a role in neutralizing the acidic components of the degrading oil, then the Test Method D 4739 result may be falsely understated.
5.3 Particular care is required in the interpretation of the base number of new and used lubricants.
5.3.1 When the base number of the new oil is required as an expression of its manufactured quality, Test Method D 2896 is preferred, since it is known to titrate weak bases that this test method may or may not titrate reliably.
5.3.2 When the base number of in-service or at-term oil is required, this test method is preferred because in many cases, especially for internal combustion engine oils, weakly basic degradation products are possible. Test Method D 2896 will titrate these, thu...
SCOPE
1.1 This test method covers a procedure for the determination of basic constituents in petroleum products and new and used lubricants. This 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 than that of the next weaker groups. This test method covers base numbers up to 250.
1.2 In new and used lubricants, the constituents that can be considered to have basic properties are primarily organic and inorganic bases, including amino compounds. This test method uses hydrochloric acid as the titrant, whereas Test Method D 2896 uses perchloric acid as the titrant. This test method may or may not titrate these weak bases and, if so, it will titrate them to a lesser degree of completion; some additives such as inhibitors or detergents may show basic characteristics.
1.3 When testing used engine lubricants, it should be recognized that certain weak bases are the result of the service rather than having been built into the oil. This test method can be used to indicate relative changes that occur in oil during use under oxidizing or other service conditions regardless of the color or other properties of the resulting oil. The values obtained, however, are intended to be compared with the other values obtained by this test method only; base numbers obtained by this test method are not intended to be equal to values by other test methods. Although the analysis is made under closely specified conditions, this test method is not intended to, and does not, result in reported basic properties that 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.
1.4 This test method was developed as an alternative for the former base number...
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An American National Standard
Designation:D4739–08
Standard Test Method for
Base Number Determination by Potentiometric Hydrochloric
1
Acid 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.
INTRODUCTION
Currently, there are two ASTM test methods under the jurisdiction of Committee D02 used for
determining base number by potentiometric titration: Test Method D2896 and Test Method D4739.
Theyarebothusedthroughoutthepetroleumindustry.TestMethodD2896isfornewoilsandisused
in setting specifications since it is more accurate thanTest Method D4739.Test Method D4739 shall
beusedexclusivelyforthepurposeoftrackingbasenumberlossasanoilproceedsinservice.Inmany
cases, the test methods will provide different results. Some comparisons are given in the Scope and
the Significance and Use sections of this test method to distinguish between the two standards and to
provide guidance to users.
1. Scope* values by other test methods. Although the analysis is made
under closely specified conditions, this test method is not
1.1 This test method covers a procedure for the determina-
intended to, and does not, result in reported basic properties
tion of basic constituents in petroleum products and new and
that can be used under all service conditions to predict
used lubricants. This test method resolves these constituents
performance of an oil; for example, no overall relationship is
into groups having weak-base and strong-base ionization
known between bearing corrosion or the control of corrosive
properties, provided the dissociation constants of the more
wear in the engine and base number.
strongly basic compounds are at least 1000 times than that of
1.4 Thistestmethodwasdevelopedasanalternativeforthe
the next weaker groups.This test method covers base numbers
former base number portion of Test Method D664 (last
up to 250.
published in Test Method D664–81).
1.2 In new and used lubricants, the constituents that can be
1.4.1 Colorimetric test methods for base number are Test
considered to have basic properties are primarily organic and
MethodD974,IP139,and5102.1onacidandbasenumberby
inorganicbases,includingaminocompounds.Thistestmethod
extraction (color-indicator titration) of Federal Test Method
uses hydrochloric acid as the titrant, whereas Test Method
Standard No. 791b. Test results by these methods may or may
D2896usesperchloricacidasthetitrant.Thistestmethodmay
not be numerically equivalent to this test method.
or may not titrate these weak bases and, if so, it will titrate
1.5 The values stated in SI units are to be regarded as
them to a lesser degree of completion; some additives such as
standard. No other units of measurement are included in this
inhibitors or detergents may show basic characteristics.
standard.
1.3 When testing used engine lubricants, it should be
1.6 This standard does not purport to address all of the
recognized that certain weak bases are the result of the service
safety concerns, if any, associated with its use. It is the
rather than having been built into the oil.This test method can
responsibility of the user of this standard to establish appro-
beusedtoindicaterelativechangesthatoccurinoilduringuse
priate safety and health practices and determine the applica-
under oxidizing or other service conditions regardless of the
bility of regulatory limitations prior to use.
color or other properties of the resulting oil. The values
obtained, however, are intended to be compared with the other
2. Referenced Documents
values obtained by this test method only; base numbers
2
2.1 ASTM Standards:
obtained by this test method are not intended to be equal to
D664 TestMethodforAcidNumberofPetroleumProducts
1
This test method is under the jurisdiction of ASTM Committee D02 on
2
PetroleumProductsandLubricantsandisthedirectresponsibilityofSubcommittee For referenced ASTM standards, visit the ASTM website, www.astm.org, or
D02.06 on Analysis of Lubricants. contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Current edition approved Feb. 1, 2008. Published April 2008. Originally Standards volume information, refer to the standard’s Document Summary page on
approved in 1987. Last previous edition approved in 2006 as D4739–06a. the ASTM website.
*A Summary of Changes section appears at the end of this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
1
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D4739–08
by Potentiometric Titration 5.2 As stat
...
This document is not anASTM standard and is intended only to provide the user of anASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
An American National Standard
Designation:D4739–06a Designation:D4739–08
Standard Test Method for
Base Number Determination by Potentiometric Hydrochloric
1
Acid 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.
INTRODUCTION
Currently, there are two ASTM test methods under the jurisdiction of Committee D02 used for
determining base number by potentiometric titration: Test Method D2896 and Test Method D4739.
Theyarebothusedthroughoutthepetroleumindustry.TestMethodD2896isfornewoilsandisused
in setting specifications since it is more accurate thanTest Method D4739.Test Method D4739 shall
beusedexclusivelyforthepurposeoftrackingbasenumberlossasanoilproceedsinservice.Inmany
cases, the test methods will provide different results. Some comparisons are given in the Scope and
the Significance and Use sections of this test method to distinguish between the two standards and to
provide guidance to users.
1. Scope*
1.1This 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.
1.1.1This 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.
NOTE1—In new and used oils, the constituents which can be considered to have basic properties are primarily organic and inorganic bases, including
aminocompounds,althoughcertainsaltsofheavymetals,saltsofweakacids,basicsaltsofpolyacidiccompounds,andsomeadditivessuchasinhibitors
or detergents may show basic characteristics.
1.2This 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.
NOTE2—TestMethodD4739wasdevelopedasanalternativefortheformerbasenumberportionofTestMethodD664.Basenumbersobtainedbythis
method may or may not be numerically the same as those obtained by the former base number portion of Test Method D664.
NOTE3—A color indicator titration method is also available in the Test Method D974 and IP139. The base numbers obtained by the potentiometric
method may or may not be numerically the same as those obtained byTest Method D974 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 D2896.
1.3The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4
1.1 This test method covers a procedure for the determination of basic constituents in petroleum products and new and used
lubricants. This 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 than that of the next weaker
groups. This test method covers base numbers up to 250.
1.2 In new and used lubricants, the constituents that can be considered to have basic properties are primarily organic and
inorganic bases, including amino compounds.This test method uses hydrochloric acid as the titrant, whereasTest Method D2896
usesperchloricacidasthetitrant.Thistestmethodmayormaynottitratetheseweakbasesand,ifso,itwilltitratethemtoalesser
1
This test method is under the jurisdiction ofASTM Committee D02 on Petroleum Products and Lubricants and is the direct responsibility of Subcommittee D02.06 on
Analysis of Lubricants.
Current edition approved Nov.Feb. 1, 2006.2008. Published November 2006.April 2008. Originally approved in 1987. Last previou
...
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