ASTM D7637-10(2021)

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: D7637 − 10 (Reapproved 2021)
Standard Test Method for
Determination of Glycerin Assay by Titration (Sodium Meta
Periodate)
This standard is issued under the fixed designation D7637; 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 2.2 Other Standards:
The United States Pharmacopoeia 31 Glycerin Monograph –
1.1 Thistestmethodprovidesthequantitativedetermination
Assay Method
of glycerin by the titrimetric method. It is applicable to all
AOCS Official Method EA6-94 (ReplacesAOCS EA6-51),
glycerin or glycerin/water mixtures >75 %. 4
Determination of Crude Glycerin, Titrimetric Method
BS 5711: Part 3, 1979 Sampling and Test for Glycerol -
1.2 The values stated in SI units are to be regarded as
Determination of Glycerol Content
standard. No other units of measurement are included in this
standard.
3. Terminology
1.3 This standard may involve hazardous materials,
3.1 Definitions:
operations, and equipment. This standard does not purport to
3.1.1 glycerin—propane-1,2,3-triol, C H (OH) (also
3 5 3
address all of the safety concerns associated with its use. It is
known as glycerine), 1,2,3-propanetriol, 1,2,3-
the responsibility of the user of this standard to consult the
trihydroxypropane, glyceritol, glycyl alcohol, glycerol. CAS
established and appropriate safety, health, and environmental
#56-81-5.
practices and determine the applicability of regulatory limita-
3.1.2 SMP—Sodium Meta Periodate.
tions prior to use. Specific precautions are listed in Section 8.
3.1.3 For other definitions of terms used in this test method,
1.4 This international standard was developed in accor-
refer to Terminology D4725.
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the
4. Significance and Use
Development of International Standards, Guides and Recom-
4.1 This test method is based on the cold oxidation of the
mendations issued by the World Trade Organization Technical
glycerol by sodium metaperiodate in a strong acidic medium.
Barriers to Trade (TBT) Committee.
Formaldehyde and formic acid are produced in this reaction
and the latter is used to measure the glycerol content by
2. Referenced Documents
titration with standard sodium hydroxide solution, to a pH 8.1
2.1 ASTM Standards:
6 0.1. The glycerol content is expressed as a percentage
D1193 Specification for Reagent Water (m/m).
D4725 Terminology for Engine Coolants and Related Fluids
CH OH 2 CHOH 2 CH OH12 NaIO→ (1)
2 2 4
E177 Practice for Use of the Terms Precision and Bias in
HCOOH12 HCHO12 NaIO 1H O
ASTM Test Methods
3 2
E691 Practice for Conducting an Interlaboratory Study to
4.2 Interferences—The glycerin sample should be free of
Determine the Precision of a Test Method
organic compounds with more than two hydroxyl groups on
adjacent carbon atoms (for example, sugars, glycols). These
types of compounds may produce formic acid which interferes
1 with the determination of the glycerol content.
This test method is under the jurisdiction ofASTM Committee D15 on Engine
Coolants and Related Fluids and is the direct responsibility of Subcommittee
D15.04 on Chemical Properties.
Current edition approved Sept. 1, 2021. Published September 2021. Originally
approved in 2010. Last previous edition approved in 2015 as D7637–10 (2015). Available from U.S. Pharmacopeial (USP), 12601 Twinbrook Parkway,
DOI: 10.1520/D7637-10R21. Rockville, MD 20852-1790, http://www.usp.org.
2 4
For referenced ASTM standards, visit the ASTM website, www.astm.org, or Available from American Oil Chemists’ Society (AOCS), 2710 S. Boulder,
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Urbana, IL 61802-6996, http://www.aocs.org.
Standards volume information, refer to the standard’s Document Summary page on AvailablefromTheBritishStandardsInstitution(BSI),389ChiswickHighRd.,
the ASTM website. London W4 4AL, U.K., http://www.bsigroup.com.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7637 − 10 (2021)
5. Apparatus 7.9 Potassium Iodide, aqueous solution—Dissolve 16.5 g of
potassium iodide in water to make 100 mL. Store tightly
5.1 Burette—50 mL“TypeA” unit that can deliver 30 drops
capped in a light-resistant container.
per mL and calibrated to meet the National Institute of
Standards and Technology (NIST) standards. 7.10 Starch Solution—Mix 1 g of soluble starch with suffi-
cient cold water to make a thin paste. Add 200 mL of boiling
NOTE 1— It is critical that all glassware be “Type A” and thoroughly
water, and boil for 1 min with continuous stirring. Cool, and
cleaned before use as dirty glassware will impact the analysis results.
use only the clear solution.
5.2 pH meter, fitted with glass electrode.
NOTE 4—It is recommended that freshly prepared starch solution be
NOTE 2—The pH meter should be standardized with a minimum of two
used to ensure a sharper endpoint. Commercially available, stabilized
buffer solutions at 10.0 and 7.0. (See 7.12.)
starch indicator solution may be also used in place of freshly prepared
starch.
5.3 Stirrer—preference should be given to a magnetic stir-
rer. In this case, check that it does not influence the pH meter. 7.11 Bromothymol blue indicator solution—Dissolve
100 mg of bromothymol blue in 100 mL of water to make
100 mL of indicator solution.
6. Purity of Reagents and Water
7.12 pH Buffers (7.0 6 0.01 and 10.0 6 0.01 at 25 °C)
6.1 Purity of Reagents—Reagent grade chemicals shall be
needed for pH meter standardization.
used in all tests. Unless otherwise indicated, it is intended that
all reagents conform to the specifications of the Committee on
7.13 Freshly boiled water, or equivalent. (See 6.2.)
Analytical Reagents of the American Chemical Society where
such specifications are available. Other grades may be used 8. Precautions
provided it is first ascertained that the reagent is of sufficiently
8.1 Sulfuric acid and sodium hydroxide solutions are cor-
high purity to permit its use without lessening the accuracy of
rosive. Avoid eye and skin contact.
the determination.
8.2 Please study and be aware of the Material Safety Data
6.2 Purity of Water—Unless indicated otherwise, references
Sheet and correct laboratory performance for the appropriate
to water shall be understood to mean Type II reagent water as
health and safety precautions that may apply to any of the
defined in Specification D1193.
chemicals and equipment prior to use.
NOTE3—Thepresenceofcarbondioxidecanintroduceerrors;therefore
8.3 It is the responsibility of each organization to conduct a
itisadvisabletoprepare500mLofwaterbyboilingfor5minandcooling
job hazard analysis to assess safety risks and PPE needed for
to room temperature. Check the pH of the distilled water before use. The
performance of this test method.
pHshouldbe7.0 60.1.Ifnot,adjustthepHwith0.1Nsodiumhydroxide
(NaOH)or0.1Nhydrogenchloride(HCl),whicheverisappropriate.Store
9. Procedure
the freshly boiled and neutralized water in a tightly closed container.
9.1 Sodium Periodate Solution Suitability Test—Pipet
7. Reagents
10 mLof the prepared sodium periodate solution (Reagent 7.1)
into a 250 mL volumetric flask, dilute with water to volume,
7.1 Sodium Metaperiodate, NaIO , acidic solution—
and mix.
Dissolve 60 g of sodium metaperiodate in sufficient water
containing120mLof0.1Nsulfuricacidtomake1000mL. Do
9.2 Weigh approximately 550 mg of glycerin into flask.
not heat to dissolve the periodate. If the solution is not clear,
Dissolvethesamplein50mLofwaterandpipette50mLofthe
pass it through a sintered-glass filter. Store the solution in a
dilutedperiodatesolutionpreparedin9.1.Allowthesolutionto
glass-stoppered, light-resistant container.
stand for 30 min.
7.2 Hydrochloric Acid, aqueous solution, approximately
9.3 Add 5 mL of hydrochloric acid solution (Reagent 7.2)
0.1 N.
and 10 mL of potassium iodide solution (Reagent 7.9), and
gently swirl to mix. Allow the solution to stand for 5 min.
7.3
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