ASTM D664-09
(Test Method)Standard Test Method for Acid Number of Petroleum Products by Potentiometric Titration
Standard Test Method for Acid Number of Petroleum Products by Potentiometric Titration
SIGNIFICANCE AND USE
New and used petroleum products, biodiesel and blends of biodiesel may contain acidic constituents that are present as additives or as degradation products formed during service, such as oxidation products. The relative amount of these materials can be determined by titrating with bases. The acid number is a measure of this amount of acidic substance in the oil, always under the conditions of the test. The acid number is used as a guide in the quality control of lubricating oil formulations. It is also sometimes used as a measure of lubricant degradation in service. Any condemning limits must be empirically established.
Since a variety of oxidation products contribute to the acid number and the organic acids vary widely in corrosion properties, the test method cannot be used to predict corrosiveness of oil or biodiesel and blends under service conditions. No general correlation is known between acid number and the corrosive tendency of biodiesel and blends or oils toward metals.
SCOPE
1.1 This test method covers procedures for the determination of acidic constituents in petroleum products, lubricants, biodiesel and blends of biodiesel.
1.1.1 Test Method A—For petroleum products and lubricants soluble or nearly soluble in mixtures of toluene and propan-2-ol. It is applicable for the determination of acids whose dissociation constants in water are larger than 10-9; extremely weak acids whose dissociation constants are smaller than 10-9 do not interfere. Salts react if their hydrolysis constants are larger than 10-9. The range of acid numbers included in the precision statement is 0.1 mg/g KOH to 150 mg/g KOH.
1.1.2 Test Method B—Developed specifically for biodiesel and biodiesel blends with low acidity and slightly different solubility. This test method requires the use of an automatic titrator with automatic endpoint seeking capability.
Note 1—In new and used oils, the constituents that may be considered to have acidic characteristics include organic and inorganic acids, esters, phenolic compounds, lactones, resins, salts of heavy metals, salts of ammonia and other weak bases, acid salts of polybasic acids, and addition agents such as inhibitors and detergents.
1.2 The test method may be used to indicate relative changes that occur in oil during use under oxidizing conditions regardless of the color or other properties of the resulting oil. Although the titration is made under definite equilibrium conditions, the test method is not intended to measure an absolute acidic property that can be used to predict performance of oil under service conditions. No general relationship between bearing corrosion and acid number is known.
Note 2—The acid number obtained by this standard may or may not be numerically the same as that obtained in accordance with Test Methods D 974 and D 3339. There has not been any attempt to correlate this method with other non-titration methods.
Note 3—A few laboratories have made the observation that there is a difference in Test Method D 664 results when aqueous versus nonaqueous buffers are used.
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this 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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British Standard 4457
Designation:D664–09
Designation 177/96
Standard Test Method for
Acid Number of Petroleum Products by Potentiometric
1
Titration
This standard is issued under the fixed designation D664; 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 (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
numerically the same as that obtained in accordance with Test Methods
1. Scope*
D974andD3339.Therehasnotbeenanyattempttocorrelatethismethod
1.1 This test method covers procedures for the determina-
with other non-titration methods.
tion of acidic constituents in petroleum products, lubricants,
NOTE 3—A few laboratories have made the observation that there is a
biodiesel and blends of biodiesel.
difference inTest Method D664 results when aqueous versus nonaqueous
1.1.1 Test Method A—For petroleum products and lubri- buffers are used.
cants soluble or nearly soluble in mixtures of toluene and
1.3 The values stated in SI units are to be regarded as
propan-2-ol. It is applicable for the determination of acids
standard. No other units of measurement are included in this
-9
whose dissociation constants in water are larger than 10 ;
standard.
extremelyweakacidswhosedissociationconstantsaresmaller
1.4 This standard does not purport to address all of the
-9
than 10 do not interfere. Salts react if their hydrolysis
safety concerns, if any, associated with its use. It is the
-9
constants are larger than 10 . The range of acid numbers
responsibility of the user of this standard to establish appro-
included in the precision statement is 0.1 mg/g KOH to 150
priate safety and health practices and determine the applica-
mg/g KOH.
bility of regulatory limitations prior to use.
1.1.2 Test Method B—Developed specifically for biodiesel
and biodiesel blends with low acidity and slightly different 2. Referenced Documents
2
solubility. This test method requires the use of an automatic
2.1 ASTM Standards:
titrator with automatic endpoint seeking capability.
D974 Test Method for Acid and Base Number by Color-
Indicator Titration
NOTE 1—In new and used oils, the constituents that may be considered
D1193 Specification for Reagent Water
to have acidic characteristics include organic and inorganic acids, esters,
phenolic compounds, lactones, resins, salts of heavy metals, salts of
D3339 Test Method for Acid Number of Petroleum Prod-
ammoniaandotherweakbases,acidsaltsofpolybasicacids,andaddition
ucts by Semi-Micro Color Indicator Titration
agents such as inhibitors and detergents.
D4057 Practice for Manual Sampling of Petroleum and
1.2 The test method may be used to indicate relative Petroleum Products
changesthatoccurinoilduringuseunderoxidizingconditions
D4177 Practice for Automatic Sampling of Petroleum and
regardless of the color or other properties of the resulting oil. Petroleum Products
Although the titration is made under definite equilibrium
3. Terminology
conditions, the test method is not intended to measure an
absolute acidic property that can be used to predict perfor- 3.1 Definitions:
mance of oil under service conditions. No general relationship 3.1.1 acid number, n—the quantity of base, expressed as
between bearing corrosion and acid number is known. milligrams of potassium hydroxide per gram of sample, re-
quired to titrate a sample in a specified solvent to a specified
NOTE 2—Theacidnumberobtainedbythisstandardmayormaynotbe
end point.
3.1.1.1 Discussion—Thistestmethodexpressesthequantity
1
This test method is under the jurisdiction of ASTM Committee D02 on
of base as milligrams of potassium hydroxide per gram of
PetroleumProductsandLubricantsandisthedirectresponsibilityofSubcommittee
D02.06 on Analysis of Lubricants.
Current edition approved March 1, 2009. Published March 2009. Originally
2
approved in 1942. Last previous edition approved in 2007 as D664–07. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
This test method was adopted as a jointASTM-IPstandard in 1964.ASTMTest contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Method D4739 has been developed as an alternative to the base number portion of Standards volume information, refer to the standard’s Document Summary page on
D664. DOI: 10.1520/D0664-09. 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.
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D664–09
sample, that is required to titrate a sample in a mixture of betw
...
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:D664–07 Designation:D664–09 British Standard 4457
Designation 177/96
Standard Test Method for
Acid Number of Petroleum Products by Potentiometric
1
Titration
This standard is issued under the fixed designation D664; 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 (´) 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. Scope*
1.1 This test method covers procedures for the determination of acidic constituents in petroleum products, lubricants, biodiesel
and blends of biodiesel.
1.1.1 Test Method A—For petroleum products and lubricants soluble or nearly soluble in mixtures of toluene and propan-2-ol.
-9
It is applicable for the determination of acids whose dissociation constants in water are larger than 10 ; extremely weak acids
-9 -9
whosedissociationconstantsaresmallerthan10 donotinterfere.Saltsreactiftheirhydrolysisconstantsarelargerthan10 .The
range of acid numbers included in the precision statement is 0.1 mg/g KOH to 150 mg/g KOH.
1.1.2 TestMethodB—Developedspecificallyforbiodieselandbiodieselblendswithlowacidityandslightlydifferentsolubility.
This test method requires the use of an automatic titrator with automatic endpoint seeking capability.
NOTE 1—In new and used oils, the constituents that may be considered to have acidic characteristics include organic and inorganic acids, esters,
phenolic compounds, lactones, resins, salts of heavy metals, salts of ammonia and other weak bases, acid salts of polybasic acids, and addition agents
such as inhibitors and detergents.
1.2 The test method may be used to indicate relative changes that occur in oil during use under oxidizing conditions regardless
of the color or other properties of the resulting oil. Although the titration is made under definite equilibrium conditions, the test
method is not intended to measure an absolute acidic property that can be used to predict performance of oil under service
conditions. No general relationship between bearing corrosion and acid number is known.
NOTE 2—TheacidnumberobtainedbythisstandardmayormaynotbenumericallythesameasthatobtainedinaccordancewithTestMethodsD974
and D3339. There has not been any attempt to correlate this method with other non-titration methods.
NOTE 3—AfewlaboratorieshavemadetheobservationthatthereisadifferenceinTestMethodD664resultswhenaqueousversusnonaqueousbuffers
are used.
1.3The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this 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.
2. Referenced Documents
2
2.1 ASTM Standards:
D974 Test Method for Acid and Base Number by Color-Indicator Titration
D1193 Specification for Reagent Water
D3339 Test Method for Acid Number of Petroleum Products by Semi-Micro Color Indicator Titration
D4057 Practice for Manual Sampling of Petroleum and Petroleum Products
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.
´1
Current edition approved July 1, 2007. Published July 2007. Originally approved in 1942. Last previous edition approved in 2006 as D664–06a .
Current edition approved March 1, 2009. Published March 2009. Originally approved in 1942. Last previous edition approved in 2007 as D664–07.
ThistestmethodwasadoptedasajointASTM-IPstandardin1964.ASTMTestMethodD4739hasbeendevelopedasanalternativetothebasenumberportionofD664.
2
ForreferencedASTMstandards,visittheASTMwebsite,www.astm.org,orcontactASTMCustomerServiceatservice@astm.org.For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on 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.
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