ASTM D7638-10

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: D7638 − 10
StandardTest Method for
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Determination of Fatty Acids and Esters in Glycerin
This standard is issued under the fixed designation D7638; 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 4. Significance and Use
1.1 Thistestmethodprovidesthequantitativedetermination 4.1 Any residual fatty acid and esters (FA&E) should be
of the fatty acid and ester content in purified glycerin by the present only at very low levels in purified glycerine.
titrimetric method.
4.2 This procedure requires the addition of a measured
1.2 The values stated in SI units are to be regarded as the volume of sodium hydroxide, in excess of the amount actually
standard. The values given in parentheses are for information needed to react with FA&E in the glycerine sample. After
only. boiling, the excess sodium hydroxide is back titrated with
standardized hydrochloric acid. The quantity of the substance
1.3 This standard may involve hazardous materials, opera-
being titrated is calculated as the difference between the
tions and equipment. This standard does not purport to address
volumes of the sodium hydroxide solution originally added,
all of the safety concerns, if any, associated with its use. It is
corrected by means of a blank titration, and that was consumed
the responsibility of the user of this standard to establish
by the titrant in the back titration.
appropriate safety and health practices and determine the
applicability of regulatory limitations prior to use. Specific
NOTE 1—The standardized solutions for sodium hydroxide and hydro-
chloric acid are commercially available.
precautions are listed in Section 8.
5. Apparatus
2. Referenced Documents
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5.1 Standard Type A Glassware.
2.1 ASTM Standards:
D1193 Specification for Reagent Water
5.2 Erlenmeyer flask, 200 to 250 mL, alkali-resistant with a
D4725 Terminology for Engine Coolants and Related Fluids
standard tapered 24/40 ground glass neck joint, or equivalent.
2.2 Other Standards:
5.3 Microburette having a capacity of 5 mL, graduated to
The United States Pharmacopoeia 31 Glycerin Monograph –
0.02 mL and calibrated to meet the NIST specification. An
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Fatty Acids and Esters
automatictitratorwithaminimumcapacityof5mLcanalsobe
used.
3. Terminology
5.4 Pipette, standard or automatic that can accurately de-
3.1 Definitions:
liver 5 6 0.01 mL.
3.1.1 glycerin—propane-1,2,3-Triol, C H (OH) (also
3 5 3
5.5 Air reflux condenser with standard taper ground glass
known as glycerine), 1,2,3-propanetriol, 1,2,3-
joint which fits the Erlenmeyer flask in 5.1. Minimum length,
trihydroxypropane, glyceritol, glycyl alcohol. CAS #56-81-5
550 mm.
3.1.2 FA&E—Fatty acid and Esters
3.1.3 For other definitions of terms used in this
6. Purity of Reagents and Water
specification, refer to Terminology D4725.
6.1 Purity of Reagents—Reagent grade chemicals shall be
used in all tests. Unless otherwise indicated, it is intended that
all reagents conform to the specifications of the Committee on
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This test method is under the jurisdiction ofASTM Committee D15 on Engine
Analytical Reagents of the American Chemical Society where
Coolants and Related Fluids and is the direct responsibility of Subcommittee
such specifications are available. Other grades may be used
D15.93 on Research and Long Range Planning.
Current edition approved June 1, 2010. Published July 2010. DOI: 10.1520/
provided it is first ascertained that the reagent is of sufficiently
D7638–10.
high purity to permit its use without lessening the accuracy of
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For referenced ASTM standards, visit the ASTM website, www.astm.org, or
the determination.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
6.2 Purity of Water—Unless indicated otherwise, references
the ASTM website.
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to water shall be understood to mean Type II reagent water as
Available from U.S. Pharmacopeia (USP), 12601 Twinbrook Pkwy., Rockville,
MD 20852-1790, http://www.usp.org. defined in Specification D1193.
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D7638 − 10
NOTE2—Thepresenceofcarbondioxidecanintroduceerrors;therefore (>0.4), the sample is inclined to foam up the condenser. The addition of
it is advisable to prepare 500 mL of water by boiling for 5 min. Cool to boiling chips helps control this problem.
room temperature. Check the pH of the distilled water before use. The pH
9.5 Place the flask on the heat source and clamp the
...