ASTM D6423-08
(Test Method)Standard Test Method for Determination of pHe of Ethanol, Denatured Fuel Ethanol, and Fuel Ethanol (Ed75-Ed85)
Standard Test Method for Determination of pHe of Ethanol, Denatured Fuel Ethanol, and Fuel Ethanol (Ed75-Ed85)
SIGNIFICANCE AND USE
The acid strength, as measured by pHe, is a good predictor of the corrosion potential of ethanol fuels. It is preferable to total acidity because total acidity does not measure acid strength; overestimates the contribution of weak acids, such as carbonic acid; and may underestimate the corrosion potential of low concentrations of strong acids, such as sulfuric acid.
SCOPE
1.1 This test method covers a procedure to determine a measure of the acid strength of high ethanol content fuels. These include ethanol, denatured fuel ethanol, and fuel ethanol (Ed75-Ed85). The test method is applicable to fuels containing nominally 70 volume % ethanol, or higher, as described in Specifications D 4806 and D 5798.
1.2 Acid strength as measured in this test method is defined as pHe. A pHe value for alcohol solutions is not comparable to pH values of water solutions. For example, a 1.5×10-5 M (18 ppm) solution of H2SO4 gives a pH of about 5.5 in water solution, but, depending on buffering strength, a pHe as low as 1 to 2 in unadditized alcohol fuel.
1.3 The value of pHe measured will depend somewhat on the fuel blend, the stirring rate, and the time the electrode is in the fuel.
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.5 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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Designation: D6423 − 08
StandardTest Method for
Determination of pHe of Ethanol, Denatured Fuel Ethanol,
1
and Fuel Ethanol (Ed75-Ed85)
This standard is issued under the fixed designation D6423; 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. Scope* Fuel Automotive Spark-Ignition Engines
1.1 This test method covers a procedure to determine a
3. Terminology
measure of the acid strength of high ethanol content fuels.
Theseincludeethanol,denaturedfuelethanol,andfuelethanol
3.1 Definitions:
(Ed75-Ed85).The test method is applicable to fuels containing
3.1.1 denaturants, n—natural gasoline, gasoline
nominally 70 volume % ethanol, or higher, as described in
components, unleaded gasoline, or toxic or noxious materials
Specifications D4806 and D5798.
addedtofuelethanoltomakeitunsuitableforbeverageusebut
1.2 Acid strength as measured in this test method is defined not unsuitable for automotive fuel use.
as pHe.ApHe value for alcohol solutions is not comparable to
3.1.2 denatured fuel ethanol, n—fuel ethanol made unfit for
-5
pH values of water solutions. For example, a 1.5×10 M (18
beverage use by the addition of denaturants.
ppm) solution of H SO gives a pH of about 5.5 in water
2 4
3.1.3 ethanol, n—ethyl alcohol, the chemical compound,
solution, but, depending on buffering strength, a pHe as low as
C H OH.
1 to 2 in unadditized alcohol fuel.
2 5
1.3 The value of pHe measured will depend somewhat on 3.1.4 fuel ethanol (Ed75-Ed85), n—a blend of ethanol and
the fuel blend, the stirring rate, and the time the electrode is in hydrocarbons of which the ethanol portion is nominally 75 to
the fuel.
85 volume % denatured ethanol.
1.4 The values stated in SI units are to be regarded as 3.2 Definitions of Terms Specific to This Standard:
standard. No other units of measurement are included in this
3.2.1 pHe,n—ameasureoftheacidstrengthofalcoholfuels
standard.
defined by this apparatus and procedure.
1.5 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
4. Summary of Test Method
responsibility of the user of this standard to establish appro-
4.1 The sample is analyzed at room temperature using a
priate safety and health practices and determine the applica-
specified electrode system and a pH meter with an input
bility of regulatory limitations prior to use.
12
impedance >10 ohms. Meters designed for use with ion-
specific electrodes normally meet this criteria.
2. Referenced Documents
2
4.2 Readings are taken at exactly 30 s because the meter
2.1 ASTM Standards:
reading will change throughout the analysis due to glass-
D4806Specification for Denatured Fuel Ethanol for Blend-
electrode voltage drift caused by dehydration of the glass-
ing with Gasolines for Use asAutomotive Spark-Ignition
electrode membrane. Because alcohol dehydrates the glass-
Engine Fuel
electrode membrane, time spent soaking in alcohol solution
D5798Specification for Ethanol Fuel Blends for Flexible-
should be minimized.
4.3 The electrode is soaked in water-based pH 7 buffer
1
This test method is under the jurisdiction of ASTM Committee D02 on
between readings to prepare it for the next sample. This
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of
rehydrates the glass electrode, a necessary step to preserve the
Subcommittee D02.A0.02 on Oxygenated Fuels and Components.
Current edition approved Dec. 15, 2008. Published February 2009. Originally
electrode’s response characteristics.
approved in 1999. Last previous edition approved in 2004 as D6423–99(2004).
DOI: 10.1520/D6423-08.
4.4 The electrodes are cleaned/rehydrated at least every ten
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
samples by alternately soaking several times in 1 M NaOH
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
solutionand1MH SO (or1MHCl)forabout30seach.New
Standards volume information, refer to the standard’s Document Summary page on 2 4
the ASTM website. electrodes are treated by this procedure before first use.
*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
---------------------- Page: 1 ----------------------
D6423 − 08
5. Significance and Use 7. Reagents and Materials
5.1 The acid strength, as measured by pHe, is a good 7.1 Purity of Reagents—Reagent grade chemicals shall be
predictor of the corrosion potential of ethanol fuels. It is used in all tests. Unless otherwise indicated, it is inten
...
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:D6423–99 (Reapproved 2004) Designation: D 6423 – 08
Standard Test Method for
Determination of pHe of Ethanol, Denatured Fuel Ethanol,
1
and Fuel Ethanol (Ed75-Ed85)
This standard is issued under the fixed designation D 6423; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope*
1.1 Thistestmethodcoversaproceduretodetermineameasureoftheacidstrengthofhighethanolcontentfuels.Theseinclude
ethanol, denatured fuel ethanol, and fuel ethanol (Ed75-Ed85). The test method is applicable to fuels containing nominally 70
volume % ethanol, or higher, as described in Specifications D 4806 and D 5798.
1.2Acid strength as measured in this test method is defined as pHe.ApHe value for alcohol solutions is not directly comparable
to pH values of water solutions.
1.3The value of pHe will depend somewhat on the fuel blend, the stirring rate, and the time the electrode is in the fuel.
1.4
1.2 Acid strength as measured in this test method is defined as pHe.ApHe value for alcohol solutions is not comparable to pH
-5
values of water solutions. For example, a 1.5310 M (18 ppm) solution of H SO gives a pH of about 5.5 in water solution, but,
2 4
depending on buffering strength, a pHe as low as 1 to 2 in unadditized alcohol fuel.
1.3 The value of pHe measured will depend somewhat on the fuel blend, the stirring rate, and the time the electrode is in the
fuel.
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.5 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:
D 4806 Specification for Denatured Fuel Ethanol for Blending with Gasolines for Use as Automotive Spark-Ignition Engine
Fuel
D 5798 Specification for Fuel Ethanol (Ed75-Ed85) for Automotive Spark-Ignition Engines
3. Terminology
3.1 Definitions:
3.1.1 ethanol, n—ethyl alcohol, the chemical compound, C H OH.
2 5
3.1.2denaturants, n—natural gasoline, gasoline components, unleaded gasoline, or toxic or noxious materials added to fuel
ethanol to make it unsuitable for beverage use but not unsuitable for automotive fuel use.
3.1.3
3.1.2 denatured fuel ethanol, n—fuel ethanol made unfit for beverage use by the addition of denaturants.
3.1.3 ethanol, n—ethyl alcohol, the chemical compound, C H OH.
2 5
3.1.4 fuel ethanol (Ed75-Ed85), n—a blend of ethanol and hydrocarbons of which the ethanol portion is nominally 75 to 85
volume % denatured ethanol.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 pHe, n—a measure of the acid strength of alcohol fuels defined by this apparatus and procedure.
4. Summary of Test Method
4.1The sample is analyzed at room temperature using a specified electrode system and a pH meter with a sufficiently high
1
This test method is under the jurisdiction ofASTM Committee D02 on Petroleum Products and Lubricants and is the direct responsibility of Subcommittee D02.A0.01
on Gasoline and Oxygenated Fuels.Gasoline-Oxygenate Blends.
Current edition approved July 1, 2004.Dec. 15, 2008. Published July 2004.February 2009. Originally approved in 1999. Last previous edition approved in 19992004 as
D6423-99.D 6423–99(2004).
2
For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at service@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.
1
---------------------- Page: 1 ----------------------
D6423–08
impedance and recommended for use with ion-specific electrodes.
4.2Readings are taken at exactly 30 s because the meter reading will drift throughout the analysis due to solvent effects on the
electrode.
4.1 The sample is analyzed at room temperature using a specified electrode system and a pH meter with an input impedance
12
>10 ohms. Meters designed for use wtih ion-specific electrodes normally me
...
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:D6423–99 (Reapproved 2004) Designation: D 6423 – 08
Standard Test Method for
Determination of pHe of Ethanol, Denatured Fuel Ethanol,
1
and Fuel Ethanol (Ed75-Ed85)
This standard is issued under the fixed designation D 6423; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope*
1.1 Thistestmethodcoversaproceduretodetermineameasureoftheacidstrengthofhighethanolcontentfuels.Theseinclude
ethanol, denatured fuel ethanol, and fuel ethanol (Ed75-Ed85). The test method is applicable to fuels containing nominally 70
volume % ethanol, or higher, as described in Specifications D 4806 and D 5798.
1.2Acid strength as measured in this test method is defined as pHe.ApHe value for alcohol solutions is not directly comparable
to pH values of water solutions.
1.3The value of pHe will depend somewhat on the fuel blend, the stirring rate, and the time the electrode is in the fuel.
1.4
1.2 Acid strength as measured in this test method is defined as pHe.ApHe value for alcohol solutions is not comparable to pH
-5
values of water solutions. For example, a 1.5310 M (18 ppm) solution of H SO gives a pH of about 5.5 in water solution, but,
2 4
depending on buffering strength, a pHe as low as 1 to 2 in unadditized alcohol fuel.
1.3 The value of pHe measured will depend somewhat on the fuel blend, the stirring rate, and the time the electrode is in the
fuel.
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.5 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:
D 4806 Specification for Denatured Fuel Ethanol for Blending with Gasolines for Use as Automotive Spark-Ignition Engine
Fuel
D 5798 Specification for Fuel Ethanol (Ed75-Ed85) for Automotive Spark-Ignition Engines
3. Terminology
3.1 Definitions:
3.1.1 ethanol, n—ethyl alcohol, the chemical compound, C H OH.
2 5
3.1.2denaturants, n—natural gasoline, gasoline components, unleaded gasoline, or toxic or noxious materials added to fuel
ethanol to make it unsuitable for beverage use but not unsuitable for automotive fuel use.
3.1.3
3.1.2 denatured fuel ethanol, n—fuel ethanol made unfit for beverage use by the addition of denaturants.
3.1.3 ethanol, n—ethyl alcohol, the chemical compound, C H OH.
2 5
3.1.4 fuel ethanol (Ed75-Ed85), n—a blend of ethanol and hydrocarbons of which the ethanol portion is nominally 75 to 85
volume % denatured ethanol.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 pHe, n—a measure of the acid strength of alcohol fuels defined by this apparatus and procedure.
4. Summary of Test Method
4.1The sample is analyzed at room temperature using a specified electrode system and a pH meter with a sufficiently high
1
This test method is under the jurisdiction ofASTM Committee D02 on Petroleum Products and Lubricants and is the direct responsibility of Subcommittee D02.A0.01
on Gasoline and Oxygenated Fuels.Gasoline-Oxygenate Blends.
Current edition approved July 1, 2004.Dec. 15, 2008. Published July 2004.February 2009. Originally approved in 1999. Last previous edition approved in 19992004 as
D6423-99.D 6423–99(2004).
2
For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at service@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.
1
---------------------- Page: 1 ----------------------
D6423–08
impedance and recommended for use with ion-specific electrodes.
4.2Readings are taken at exactly 30 s because the meter reading will drift throughout the analysis due to solvent effects on the
electrode.
4.1 The sample is analyzed at room temperature using a specified electrode system and a pH meter with an input impedance
12
>10 ohms. Meters designed for use wtih ion-specific electrodes normally me
...
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