ASTM D8031-16

Standard Test Method for Acid Number of Terephthalic Acid (TA) by Automatic Potentiometric Titration

SIGNIFICANCE AND USE
5.1 An estimate of TA purity can be determined by titrating with KOH. As an index of TA purity, the acid number can be used as a guide in the quality control of TA production.
SCOPE
1.1 This test method covers the determination of acid number in terephthalic acid (TA) by automatic potentiometric titration. As the index of TA purity, acid number is usually within 674 to 676 mg KOH/g.  
1.2 In determining the conformance of the test results using this method, results shall be rounded off in accordance with the rounding-off method of Practice E29.  
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.

General Information

• Status: Published
• Publication Date: 29-Feb-2016
• ICS: 71.080.40 - Organic acids
• Technical Committee: D16 - Aromatic, Industrial, Specialty and Related Chemicals
• Drafting Committee: D16.02 - Oxygenated Aromatics

Relations

• Refers: ASTM D6809-02(2016) - Standard Guide for Quality Control and Quality Assurance Procedures for Aromatic Hydrocarbons and Related Materials
• Effective Date: 01-Nov-2016
• Refers: ASTM D4790-14 - Standard Terminology of Aromatic Hydrocarbons and Related Chemicals
• Effective Date: 01-Jul-2014
• Refers: ASTM D664-11a(2017) - Standard Test Method for Acid Number of Petroleum Products by Potentiometric Titration
• Effective Date: 01-May-2017

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.
Designation: D8031 − 16
Standard Test Method for
Acid Number of Terephthalic Acid (TA) by Automatic
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Potentiometric Titration
This standard is issued under the fixed designation D8031; 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 E691 Practice for Conducting an Interlaboratory Study to
Determine the Precision of a Test Method
1.1 This test method covers the determination of acid
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2.2 Other Document:
number in terephthalic acid (TA) by automatic potentiometric
OSHA Regulations, 29 CFR paragraphs 1910.1000 and
titration. As the index of TA purity, acid number is usually
1910.1200
within 674 to 676 mg KOH/g.
1.2 In determining the conformance of the test results using
3. Terminology
this method, results shall be rounded off in accordance with the
3.1 Definitions:
rounding-off method of Practice E29.
3.1.1 acid number, n—the quantity of base, expressed as
1.3 The values stated in SI units are to be regarded as
milligrams of potassium hydroxide per gram of sample that is
standard. No other units of measurement are included in this
required to titrate a sample in a specified solvent to a specified
standard.
end point.
1.4 This standard does not purport to address all of the
4. Summary of Test Method
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro- 4.1 ATAsample is dissolved in pyridine, diluted with water
and titrated potentiometrically with standard sodium hydroxide
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use. solution, using a glass indicating electrode and a reference
electrode or a combination electrode. The meter readings are
2. Referenced Documents
plotted automatically against the respective volumes of titrat-
2 ing solution and the end points are taken only at well-defined
2.1 ASTM Standards:
inflectionsintheresultingcurve.Theacidnumberiscalculated
D664 Test Method for Acid Number of Petroleum Products
as milligrams of KOH per gram of TA sample. Its theoretical
by Potentiometric Titration
value of TA sample is 675.5 mg KOH/g.
D1193 Specification for Reagent Water
D4790 Terminology ofAromatic Hydrocarbons and Related
5. Significance and Use
Chemicals
5.1 An estimate of TApurity can be determined by titrating
D6809 Guide for Quality Control and Quality Assurance
with KOH. As an index of TA purity, the acid number can be
Procedures for Aromatic Hydrocarbons and Related Ma-
used as a guide in the quality control of TA production.
terials
E29 Practice for Using Significant Digits in Test Data to
6. Apparatus
Determine Conformance with Specifications
6.1 Analytical Balance.
E177 Practice for Use of the Terms Precision and Bias in
ASTM Test Methods
6.2 Automatic Potentiometric Titrator—Automatic titration
E300 Practice for Sampling Industrial Chemicals
systems capable of adding fixed increments of titrant at fixed
time intervals (monotonic) or variable titrant increments with
electrode stability between increment additions (dynamic) with
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This test method is under the jurisdiction of ASTM Committee D16 on
endpoint seeking capabilities as prescribed in the method.As a
Aromatic Hydrocarbons and Related Chemicals and is the direct responsibility of
minimum, the apparatus shall meet the performance and
Subcommittee D16.02 on Oxygenated Aromatics.
specification requirements as warranted by the manufacturer.
Current edition approved March 1, 2016. Published June 2016. DOI: 10.1520/
D8031-16.
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For referenced ASTM standards, visit the ASTM website, www.astm.org, or
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contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Available from U.S. Government Printing Office, Superintendent of
Standards volume information, refer to the standard’s Document Summary page on Documents, 732 N. Capitol St., NW, Washington, DC 20401-0001, http://
the ASTM website. www.access.gpo.gov.
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D8031 − 16
6.2.1 Amonotonic or dynamic mode of titrant shall be used. 8. Hazards
During the titration, the speed and volume of the addition may
8.1 Consult current federal regulations, supplier’s Safety
vary depending on the rate of change of the system. The
Data Sheets, and local regulations for all materials used in this
recommended maximum volume increment
...