ASTM D664-06
(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
SCOPE
1.1 This test method covers procedures for the determination of acidic constituents in 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.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.
1.3 &si-value;
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:D664–06 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 (e) 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* 1.4 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 procedures for the determina-
responsibility of the user of this standard to establish appro-
tionofacidicconstituentsinpetroleumproductsandlubricants
priate safety and health practices and determine the applica-
soluble or nearly soluble in mixtures of toluene and propan-2-
bility of regulatory limitations prior to use.
ol. It is applicable for the determination of acids whose
-9
dissociation constants in water are larger than 10 ; extremely
2
2. Referenced Documents
-9
weak acids whose dissociation constants are smaller than 10
2.1 ASTM Standards:
do not interfere. Salts react if their hydrolysis constants are
-9
D974 Test Method for Acid and Base Number by Color-
larger than 10 . The range of acid numbers included in the
Indicator Titration
precision statement is 0.1 mg/g KOH to 150 mg/g KOH.
D1193 Specification for Reagent Water
NOTE 1—In new and used oils, the constituents that may be considered
D3339 Test Method for Acid Number of Petroleum Prod-
to have acidic characteristics include organic and inorganic acids, esters,
ucts by Semi-Micro Color Indicator Titration
phenolic compounds, lactones, resins, salts of heavy metals, salts of
D4057 Practice for Manual Sampling of Petroleum and
ammoniaandotherweakbases,acidsaltsofpolybasicacids,andaddition
Petroleum Products
agents such as inhibitors and detergents.
D4177 Practice for Automatic Sampling of Petroleum and
1.2 The test method may be used to indicate relative
Petroleum Products
changesthatoccurinoilduringuseunderoxidizingconditions
regardless of the color or other properties of the resulting oil.
3. Terminology
Although the titration is made under definite equilibrium
3.1 Definitions:
conditions, the test method is not intended to measure an
3.1.1 acid number, n—the quantity of base, expressed as
absolute acidic property that can be used to predict perfor-
milligrams of potassium hydroxide per gram of sample, re-
mance of oil under service conditions. No general relationship
quired to titrate a sample in a specified solvent to a specified
between bearing corrosion and acid number is known.
end point.
NOTE 2—Theacidnumberobtainedbythisstandardmayormaynotbe 3.1.1.1 Discussion—Thistestmethodexpressesthequantity
numerically the same as that obtained in accordance with Test Methods
of base as milligrams of potassium hydroxide per gram of
D974 and D3339. There has not been any attempt to correlate this
sample, that is required to titrate a sample in a mixture of
method with other non-titration methods.
toluene and propan-2-ol to which a small amount of water has
1.3 The values stated in SI units are to be regarded as the
been added from its initial meter reading in millivolts to a
standard. The values given in parentheses are for information
meter reading in millivolts corresponding to an aqueous basic
only.
buffersolutionorawell-definedinflectionpointasspecifiedin
the test method.
3.1.1.2 Discussion—This test method provides additional
information. The quantity of base, expressed as milligrams of
1
This test method is under the jurisdiction of ASTM Committee D02 on
PetroleumProductsandLubricantsandisthedirectresponsibilityofSubcommittee
D02.06 on Analysis of Lubricants.
Current edition approved Jan. 1, 2006. Published February 2006. Originally
e1 2
approved in 1942. Last previous edition approved in 2004 as D664–04 . 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. 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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D664–06
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electronicvoltmeterdesignedtooperateonaninputoflessthan5 310
potassium hydroxide
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