ASTM D664-18e2
(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
5.1 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.
5.2 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 D974 and D3339. 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 D664 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
General Information
Relations
Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
´2
Designation: D664 − 18 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.
1
ε NOTE—Subsection 13.3.1 and a statement in the Summary of Changes were corrected editorially in December 2018.
2
ε NOTE—Subsections 16.1.1.1 and 16.1.2.1 were corrected editorially in January 2019.
This standard has been approved for use by agencies of the U.S. Department of Defense.
NOTE2—Theacidnumberobtainedbythisstandardmayormaynotbe
1. Scope*
numerically the same as that obtained in accordance with Test Methods
1.1 This test method covers procedures for the determina-
D974andD3339.Therehasnotbeenanyattempttocorrelatethismethod
tion of acidic constituents in petroleum products, lubricants, with other non-titration methods.
NOTE 3—A few laboratories have made the observation that there is a
biodiesel, and blends of biodiesel.
difference in Test Method D664 results when aqueous versus nonaqueous
1.1.1 Test Method A—Forpetroleumproductsandlubricants
buffers are used.
soluble or nearly soluble in mixtures of toluene and propan-2-
1.3 The values stated in SI units are to be regarded as
ol. It is applicable for the determination of acids whose
–9
standard. No other units of measurement are included in this
dissociation constants in water are larger than 10 ; extremely
–9
standard.
weak acids whose dissociation constants are smaller than 10
do not interfere. Salts react if their hydrolysis constants are
1.4 This standard does not purport to address all of the
–9
larger than 10 . The range of acid numbers included in the safety concerns, if any, associated with its use. It is the
precision statement is 0.1mg⁄g KOH to 150mg⁄g KOH.
responsibility of the user of this standard to establish appro-
1.1.2 Test Method B—Developed specifically for biodiesel priate safety, health, and environmental practices and deter-
and biodiesel blends with low acidity and slightly different
mine the applicability of regulatory limitations prior to use.
solubility. This test method requires the use of an automatic 1.5 This international standard was developed in accor-
titrator with automatic endpoint-seeking capability. dance with internationally recognized principles on standard-
NOTE 1—In new and used oils, the constituents that may be considered
ization established in the Decision on Principles for the
to have acidic characteristics include organic and inorganic acids, esters,
Development of International Standards, Guides and Recom-
phenolic compounds, lactones, resins, salts of heavy metals, salts of
mendations issued by the World Trade Organization Technical
ammoniaandotherweakbases,acidsaltsofpolybasicacids,andaddition
Barriers to Trade (TBT) Committee.
agents such as inhibitors and detergents.
1.2 The test method may be used to indicate relative
2. Referenced Documents
changesthatoccurinoilduringuseunderoxidizingconditions
2
2.1 ASTM Standards:
regardless of the color or other properties of the resulting oil.
D974Test Method for Acid and Base Number by Color-
Although the titration is made under definite equilibrium
Indicator Titration
conditions, the test method is not intended to measure an
D1193Specification for Reagent Water
absolute acidic property that can be used to predict perfor-
D3339TestMethodforAcidNumberofPetroleumProducts
mance of oil under service conditions. No general relationship
by Semi-Micro Color Indicator Titration
between bearing corrosion and acid number is known.
D4057Practice for Manual Sampling of Petroleum and
Petroleum Products
1
This test method is under the jurisdiction of ASTM Committee D02 on
D4177Practice for Automatic Sampling of Petroleum and
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of
Petroleum Products
Subcommittee D02.06 on Analysis of Liquid Fuels and Lubricants.
Current edition approved Nov. 1, 2018. Published November 2018. Originally
approved in 1942. Last previous edition approved in 2017 as D664 – 17a. DOI:
2
10.1520/D0664-18E02. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
This test method was adopted as a jointASTM-IPstandard in 1964.ASTM Test 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
...
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