ASTM E3334-22

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.
Designation: E3334 − 22
Standard Test Method for
Acidity in Ethanol and Ethanol Solutions
This standard is issued under the fixed designation E3334; 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 2. Referenced Documents
1.1 This test method covers the determination of acidity as 2.1 ASTM Standards:
acetic acid in ethanol and ethanol solutions. This test method D770Specification for Isopropyl Alcohol
may be applied to ethanol samples containing very little water D1193Specification for Reagent Water
(dehydrated alcohols) to solutions with significant water (low D7795Test Method for Acidity in Ethanol and Ethanol
proof ethanol samples). The solutions include denatured alco- Blends by Titration
hols such as the U.S. denatured ethanol formulas defined in E200Practice for Preparation, Standardization, and Storage
27.CFR.Part 21. This test method is used for determining low of Standard and Reagent Solutions for ChemicalAnalysis
levels of acidity, below 200 m⁄kg (ppm mass), with the
2.2 U.S. Federal Standards:
exclusion of carbon dioxide.
United States Code of Federal Regulations, Title 27, Part
1.1.1 Procedure A—Developed specifically for measure-
21Formulas for Denatured Alcohol and Rum
ment of acidity by potentiometric titration. This is the referee
United States PharmacopeiaGeneral Chapters Alcohol De-
method.
termination
1.1.2 Procedure B—Developed specifically for measure-
3. Terminology
ment of acidity by color end point titration.
3.1 Definitions:
1.2 The ethanol may be analyzed directly by this test
3.1.1 acidity, n—the quality, state, or degree of being acid.
method with minimal sample preparation.
3.1.1.1 Discussion—The amount of acid titrated with a
1.3 Review the current and appropriate Safety Data Sheets
strong base (NaOH or KOH) in a sample, calculated as acetic
(SDS) for detailed information concerning toxicity, first aid
acid in mg/kg (ppm mass).
procedures, and safety precautions and proper personal protec-
3.1.2 ethanol, n—ethyl alcohol, the chemical compound
tive equipment.
C H OH.
2 5
1.4 Units—The values stated in SI units are to be regarded
3.2 Abbreviations:
asstandard.Nootherunitsofmeasurementareincludedinthis
3.2.1 KHC H O —KHP-Potassium Hydrogen Phthalate
8 4 4
standard.
3.2.2 NaOH—Sodium Hydroxide
1.5 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the 3.2.3 KOH—Potassium Hydroxide
responsibility of the user of this standard to establish appro-
4. Summary of Test Method
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
4.1 Samples are purged with nitrogen prior to and during
Some specific hazards statements are given in Section 7 on
titrationfortheeliminationofcarbondioxideandthenaknown
Hazards.
amountofethanolsampleisanalyzedpotentiometricallyeither
1.6 This international standard was developed in accor-
using a monotonic or dynamic end point titrant addition, as
dance with internationally recognized principles on standard-
specified in Procedure A, or by color end point titration, as
ization established in the Decision on Principles for the
specified in Procedure B, using a strong base (NaOH or KOH)
Development of International Standards, Guides and Recom-
solution.Acidcontentiscalculatedasmilligramsofaceticacid
mendations issued by the World Trade Organization Technical
per kilogram of sample.
Barriers to Trade (TBT) Committee.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
This test method is under the jurisdiction of ASTM Committee E48 on contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
BioenergyandIndustrialChemicalsfromBiomassandisthedirectresponsibilityof Standards volume information, refer to the standard’s Document Summary page on
Subcommittee E48.A0 on Product Specifications. the ASTM website.
Current edition approved Jan. 1, 2022. Published February 2022. DOI: 10.1520/ Available from https://www.ecfr.gov/.
E3334-22. Available from USP, https://www.usp.org/.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E3334 − 22
5. Significance and Use 7. Hazards
5.1 This test method measures acidity quantitatively. Very
7.1 Each analyst shall be acquainted with the potential
dilute aqueous solutions of low molecular mass organic acids,
hazards of the equipment, reagents, products, solvents, and
such as acetic acid, are highly corrosive to many metals.
procedures before beginning laboratory work. Sources of
information include: instrument manuals, MSDS, various
5.2 Acceptable levels of acidity in ethanol can vary with
literature, and other related sources. Safety information should
different specifications, but in general, it is below 200mg⁄kg
(ppm). Knowledge of the acidity can be required to establish be requested from the supplier. Disposal of waste materials,
reagents, reactants, and solvents shall comply with all the laws
whether the product quality meets specification.
and regulations from all applicable governmental agencies.
6. Interferences
7.2 The following hazards are associated with the applica-
6.1 Basic titrants can absorb carbon dioxide from the air to
tion of this test method and the use of an automatic titrator.
produce carbonate ions and change the concentration of the
7.2.1 Chemical Hazard:
titrant. Care should be taken to minimize exposure of basic
titrants to the air as much as possible. Verify the concentration
7.2.1.1 A solution of potassium hydroxide or sodium hy-
of the titrant (standardize the titrant) frequently enough to droxide is corrosive and shall be handled with the appropriate
detect concentration changes of 0.0005mol⁄L (M), and espe-
personal protective equipment such as gloves, chemical
cially if prolonged exposure to the air occurs.
goggles, and lab coat or chemical-resistant apron.Always add
the base to water when diluting 50% NaOH or KOH.
6.2 Minimize exposure of the samples to the air during
7.2.1.2 Ethanolisaflammableandtoxicsolventthatisused
storage to avoid contamination by carbon dioxide. Carbon
dioxideishighlysolubleinethanol.Asasampleistitratedwith to prepare the lithium chloride electrolyte solution for the
reference electrode.When handling a flammable solvent, work
a base, the dissolved carbon dioxide can convert to carbonate
ions and provide incorrect acidity analysis. The samples are in a well-ventilated area away from all sources of ignition.
purged with nitrogen prior to and during the analysis to avoid
this interference.
PROCEDURE A—POTENTIOMETRIC TITRATION
8. Apparatus
8.1 Potentiometric Titrator—Automatic titration systems 8.5 Sensing Electrode, standard pH, suitable for non-
capable of adding fixed increments of titrant at fixed time aqueous titrations.
intervals (monotonic) or variable titrant increments with elec-
8.6 Reference Electrode—Silver/Silver Chloride (Ag/AgCl)
trode stability between increment additions (dynamic) with
Reference Electrode, filled with 1M-3M LiCl in ethanol.
endpoint seeking capabilities as prescribed in the method. At
8.7 Combination pH Electrodes—Sensing electrodes may
the very least, the automatic titration system shall meet the
have the Ag/AgCl reference electrode built into the same
performance and specification requirements as warranted by
electrode body, which offers the convenience of working with
the manufacturer.
and maintaining only one electrode. A combination pH elec-
8.2 A monotonic or dynamic mode of titrant addition shall
trode designed for nonaqueous titrations of organic solvents is
be used. During the titration, the speed and volume of the
needed for titration of ethanol and ethanol blends. The combi-
addition may vary depending on the rate of change of the
nation pH electrode shall have a sleeve junction on the
system. The recommended minimum volume increment is
reference compartment and shall use an inert ethanol
0.05mL for low acidity samples, and the recommended
electrolyte, 1mol⁄L to 3mol⁄L (M) LiCl in ethanol. Combi-
maximum volume increment is 0.1mL. A signal drift of
nation pH electrodes shall have the same or better response
10mV⁄min and endpoint recognition set to last is recom-
thanadualelectrodesystem.Theyshallhaveamovablesleeve
mendedtoensureendpointdetection.Whenusingamonotonic
for easy rinsing and addition of electrolyte.
titrant addition, the waiting time between increment additions
8.8 Titration Beaker, borosilicate glass or plastic beaker of
shall be sufficient to allow for mixing and a stable electrode
suitable size for the titration.
response. Wait at least 10s between additions.
8.9 Sparging System,anitrogengasdeliverysystemsuitable
8.3 Buret, 5mL capacity, capable of delivering titrant in
to deliver directly into the liquid sample, with an external
0.02mLor larger increments.The buret tip shall deliver titrant
pressure of 69kPa (10psi).
directly into the titration vessel without exposure to the
surrounding air. The buret used for base solutions shall have a
8.10 Variable-Speed Mechanical Stirrer, a suitable type,
guard tube containing carbon dioxide absorbent.
equipped with a propeller-type stirring paddle. The rate of
stirringshallbesufficienttoproducevigorousagitationwithout
8.4 Titration Stand, suitable for supporting the electrode,
stirrer, and buret tip. spatteringandwithoutstirringairintothesolution.Apropeller
E3334 − 22
with blades 6mm in radius and set at a pitch of 30 to 45° is tion of Solutions, Precision and Bias, and Preparation of 50 %
satisfactory.Amagnetic stirrer and stirring bar is also satisfac- NaOH Solution and of Standard Solutions sections of Practice
tory. E200.
8.10.1 If an electrical stirring apparatus is used, it shall be
9.5.1 Alternatively, KOH (0.01 N) in isopropyl alcohol
electrically correct and grounded so that connecting or discon-
solution may be used instead of 0.01 N NaOH.
necting the power to the motor will not produce a permanent
9.6 Alcohols, ethyl or isopropyl.
change in the instrument reading during the course of the
titration. NOTE 1—Isopropyl alcohol (99% grade) conforming to Specification
D770,or190proofethylalcoholconformingtoformulaNo.3AoftheU.S
Bureau ofAlcohol,Tobacco, and Firearms as defined inTitle 27, Code of
9. Reagents and Materials
Federal Regulations Part 21 (or equivalent regulations in other jurisdic-
9.1 Purity of Reagents—Reagent grade chemicals shall be
tions) is suitable for use as the solvent. The use of methyl alcohol is not
used in all tests. Unless otherwise indicated, it is intended that
recommended.
all reagents shall conform to the specifications of the commit-
9.7 Lithium Chloride Electrolyte—Prepare a 1mol⁄L to
tee onAnalytical Reagents of theAmerican Chemical Society,
3mol ⁄L(M) solution of lithium chloride (LiCl) in ethanol per
where such specifications are available. Other grades may be
the electrode manufacturer’s recommendation.
used, provided it is pure enough to be used without lessening
9.8 Nitrogen, 99.9% pure.
the accuracy of the determination.
9.1.1 Commercially available solutions may be used in
9.9 Commercial Aqueous pH 4 and pH 7 Buffer Solutions—
place of laboratory preparations provided the solutions have
Thesesolutionsshallbereplacedatregularintervalsconsistent
been certified as being equivalent.
with their stability or when contamination is suspected. Infor-
9.1.2 Alternate volumes of the solutions may be prepared,
mation relating to their stability is provided by the manufac-
provided the final solution concentration is equivalent.
turer.
9.2 Purity of Water—Unless otherwise indicated, reference
to water shall be understood to mean reagent water that meets
10. Preparation of Apparatus
the requirements of either Type II or III of Specification
10.1 Prepare the titrator in accordance with the manufactur-
D1193.
er’s instructions. Any visible air bubbles in the buret tip shall
9.2.1 Prepare CO free water by sparging 1 Lof water (9.2)
be eliminated prior to titration since this can lead to errors.
with nitrogen (9.8) for no less than 3 min.
10.2 Preparation of Electrodes—When the combination pH
9.3 Potassium Hydrogen Phthalate (KHC H O ), primary
8 4 4
electrode contains Ag/AgCl reference with an electrolyte
standard, dried—Place4gto5gof primary standard potas-
which is not 1mol⁄L to 3mol⁄L (M) LiCl in ethanol, the
sium hydrogen phthalate KHC H O of 100 mesh fineness, in
8 4 4
electrolyte shall be replaced. Drain the electrolyte from the
a weighing bottle at 120 °C for 2 h. Stopper the container and
electrode (vacuum suction), wash away all the salt (if present)
cool it in a desiccator.
with water and then rinse with ethanol. Rinse several times
9.4 Potassium Hydrogen Phthalate (KHP) Solution—
with LiCl electrolyte solution. Finally, replace the sleeve and
Accurately weigh approximately 1.0g of dried KHP and
fill the electrode with the LiCl electrolyte to the filling hole.
record the mass to the nearest 6 0.0001g and transfer it to a
When refitting the sleeve, ensure that there will be a free flow
500mLClassAvolumetric flask swept free of carbon dioxide.
of electrolyte into the system.
Add200mLofTypeIIDIwaterthatisfreeofcarbondioxide,
10.3 Maintenance and Storage of Electrodes:
stopper and swirl gently until it is dissolved. Dilute to 500mL
10.3.1 Follow the manufacturer’s instructions for storage
and mix thoroughly. Express the concentration of KHP in
and use of the electrode.
solution as Molarity in moles of KHPper litre of solution.The
10.3.2 Prior to each titration, soak the prepared electrode in
use of a volumetric flask can be avoided by weighing 1.0g of
water for at least 2min. Rinse the electrode with deionized
dried KHP to the nearest 0.0001g into a beaker and adding
water immediately prior to use. The glass membrane needs to
500gofTypeIIcarbondioxidefreeDIwater.Recordthetotal
be rehydrated after titration of non-aqueous solutions.
mass of water and KHPto the nearest 60.01g and express the
concentration of KHP in the solution as mg KHP per gram of 10.3.3 When not in use, immerse the lower half of the
solution. Mix thoroughly to dissolve the KHPand store it in a combination electrode in LiCl electrolyte. Do not allow elec-
closed container. trodestoremainimmersedinatitratedsamplesolutionforany
longer than it is necessary. While the electrodes are not
9.5 Sodium Hydroxide, Standard Solution (0.01 N)—
extremely fragile, handle them carefully at all times.
Prepare and standardize a 0.01 N sodium hydroxide (NaOH)
solution in accordance with the Preparation and Standardiza-
11. Calibration and Standardization
5 11.1 Calibration of Electrode:
Reagent Chemicals, American Chemical Society Specifications, American
Chemical Society, Washington, DC. For suggestions on the testing of reagents not 11.1.1 Select the correct electrode for the analysis (see
listed by the American Chemical Society, see Analar Standards for Laboratory
10.2).
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
11.1.2 Verify that the electrode
...