ASTM D5768-02(2006)
(Test Method)Standard Test Method for Determination of Iodine Value of Tall Oil Fatty Acids
Standard Test Method for Determination of Iodine Value of Tall Oil Fatty Acids
SIGNIFICANCE AND USE
The iodine value of a fatty acid product is a measure of the unsaturated fatty acid content of that product and consequently a measure of the ease of oxidation or drying capacity of that fatty acid product.
This test method measures the unsaturation as iodine value by addition of an iodine/chlorine reagent. The amount of reagent absorbed is determined by back titrating the excess reagent and comparing it to a blank determination.
In samples containing conjugated double bonds, the iodine value obtained is empirical since the reagent does not react stoichiometrically with conjugated unsaturation. Where no conjugation is present, the iodine value obtained is a measure of the total unsaturation. By using proper specimen weights, the empirical values obtained are useful for comparative purposes.
This test method was developed in order to replace the hazardous solvent, carbon tetrachloride, used in Test Method D 1959 with the less hazardous and more available solvents, iso-octane and cyclohexane. As data on the satisfactory use of other solvents becomes available, this test method will be amended to include those solvents.
This test method should have applicability to fatty acids and oils other than tall oil fatty acid but that possibility has not been investigated.
SCOPE
1.1 This test method covers the Wijs procedure for determination of unsaturation (iodine value) of tall oil fatty acids.
1.2 Iodine value is a measure of the unsaturation of oils and fatty acids and is expressed in terms of the number of centigrams of iodine per gram of sample (weight percent of absorbed iodine).
1.3 When this test method is used to determine the iodine value of fatty acids having conjugated systems, the result is not a measure of total unsaturated, but rather is an empirical value that affords a comparison of unsaturation. Total unsaturation of conjugated systems may be measured in accordance with Test Method D 1541.
1.4 The test method described here is not reliable for tall oil fatty acids containing an appreciable quantity of rosin.
1.5 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
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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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information.
Designation:D5768–02(Reapproved2006)
Standard Test Method for
Determination of Iodine Value of Tall Oil Fatty Acids
This standard is issued under the fixed designation D5768; 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 E177 Practice for Use of the Terms Precision and Bias in
ASTM Test Methods
1.1 This test method covers the Wijs procedure for deter-
E691 Practice for Conducting an Interlaboratory Study to
mination of unsaturation (iodine value) of tall oil fatty acids.
Determine the Precision of a Test Method
1.2 Iodine value is a measure of the unsaturation of oils and
fatty acids and is expressed in terms of the number of
3. Significance and Use
centigrams of iodine per gram of sample (weight percent of
3.1 The iodine value of a fatty acid product is a measure of
absorbed iodine).
the unsaturated fatty acid content of that product and conse-
1.3 When this test method is used to determine the iodine
quently a measure of the ease of oxidation or drying capacity
value of fatty acids having conjugated systems, the result is not
of that fatty acid product.
a measure of total unsaturated, but rather is an empirical value
3.2 This test method measures the unsaturation as iodine
that affords a comparison of unsaturation.Total unsaturation of
value by addition of an iodine/chlorine reagent. The amount of
conjugated systems may be measured in accordance with Test
reagent absorbed is determined by back titrating the excess
Method D1541.
reagent and comparing it to a blank determination.
1.4 The test method described here is not reliable for tall oil
3.3 In samples containing conjugated double bonds, the
fatty acids containing an appreciable quantity of rosin.
iodine value obtained is empirical since the reagent does not
1.5 The values stated in SI units are to be regarded as the
react stoichiometrically with conjugated unsaturation. Where
standard. The values given in parentheses are for information
no conjugation is present, the iodine value obtained is a
only.
measure of the total unsaturation. By using proper specimen
1.6 This standard does not purport to address all of the
weights, the empirical values obtained are useful for compara-
safety concerns, if any, associated with its use. It is the
tive purposes.
responsibility of the user of this standard to establish appro-
3.4 This test method was developed in order to replace the
priate safety and health practices and determine the applica-
hazardous solvent, carbon tetrachloride, used in Test Method
bility of regulatory limitations prior to use.
D1959 with the less hazardous and more available solvents,
2. Referenced Documents iso-octane and cyclohexane. As data on the satisfactory use of
2 other solvents becomes available, this test method will be
2.1 ASTM Standards:
amended to include those solvents.
D1193 Specification for Reagent Water
3.5 This test method should have applicability to fatty acids
D1541 Test Method for Total Iodine Value of Drying Oils
and oils other than tall oil fatty acid but that possibility has not
and Their Derivatives
been investigated.
D1959 Test Method for Iodine Value of Drying Oils and
Fatty Acids
4. Apparatus
4.1 Bottles—Glass-stoppered bottles or Erlenmeyer flasks
This test method is under the jurisdiction of ASTM Committee D01 on Paint
of 250-mL capacity.
and Related Coatings, Materials, andApplications and is the direct responsibility of
4.2 Pipets—20 and 25-mL capacity.
Subcommittee D01.34 on Naval Stores.
Current edition approved Nov. 1, 2006. Published November 2006. Originally
4.3 Analytical balance
approved in 1995. Last previous edition approved in 2002 as D5768 - 02. DOI:
10.1520/D5768-02R06.
5. Reagents
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
5.1 Purity of Reagents—Reagent grade chemicals shall be
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
used in all tests unless otherwise specified. Unless otherwise
the ASTM website.
indicated, it is intended that all reagents shall conform to the
Withdrawn. The last approved version of this historical standard is referenced
Specifications of the Committee onAnalytical Reagents of the
on www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D5768–02 (2006)
American Chemical Society, where such specifications are
C =Na S O solution required for titration of the
2 2 3
available. Other grades may be used provided it is first
K Cr O , mL.
2 2 7
ascertained that the reagent is of sufficiently high purity to
5.8 Starch Indicator Solution:
permit its use without lessening the accuracy of the determi-
5.8.1 Use soluble starch that will pass the following test for
nation.
sensitivity: Make a paste with1gof starch and a small amount
5.2 Purity of Water—Unless otherwise indicated, references
of cold water. Add, while stirring, 200 mL of boiling water.
to water shall be understood to mean reagent water conforming
Dilute5mLofthissolutionwith100mLofwaterandadd0.05
to Type I of Specification D1193.
mL of 0.1 N iodine solution. The deep blue color produced
5.3 Acetic Acid (Glacial) 17.4 M—Verify the absence of
must be discharged by 0.05 mL of 0.1 N Na S O solution.
2 2 3
substances reducing permanganate as follows: Dilute 2 mL of
5.8.2 Make a homogeneous paste of 10 g of soluble starch
the acid with 10 mL of water and add 0.1 mL of 0.1 N
in cold water.Add to this 1 Lof boiling water. Stir rapidly and
potassium permanganate (KMnO ) solution. The pink color
cool. Salicylic acid (1.25 g/L) may be added to preserve the
should not be entirely discharged at the end of 2 h.
indicator. If long storage is required, keep the solution in a
5.4 Iso-octane or cyclohexane.
refrigerator at 4 to 10°C (40 to 50°F). Prepare fresh indicator
5.5 Chlorine (99.8 % Cl)—(Warning: Extremely hazard-
when the end point of the titration from blue to colorless fails
ous. For specific hazard information and guidance, see suppli-
to be sharp.
er’s Material Safety Data sheets.) Commercial grades of
5.9 Wijs Solution—(Warning: Extremely hazardous. For
chlorineavailableincylindersmaybeused,providedthegasis
specific hazard information and guidance, see supplier’s Ma-
dried by passing through concentrated sulfuric acid (H SO ,sp
2 4
terial Safety Data sheets.) Dissolve 13.0 g of iodine in 1 L of
gr1.84)beforepassingitintotheiodinesolution.Alternatively,
acetic acid. Gentle heat may be necessary to promote solution.
the chlorine may be prepared by allowing concentrated hydro-
Cool and remove a small quantity (100 to 200 mL) and set
chloric acid (HCl, sp gr 1.19) to drop onto potassium perman-
aside in a cool place for future use. Pass dry chlorine gas into
ganate (KMnO ) or onto a mixture of KMnO and manganese
4 4
the iodine solution until the original titration is not quite
dioxide (MnO ). Dry the gas thus generated by passing it
doubled. A characteristic color change takes place in the Wijs
through concentrated H SO .
2 4
solution when the desired amount of chlorine has been added;
5.6 Potassium Iodide Solution (150 g/L)—Dissolve150gof
this may be used to assist in judging the end point. A
potassium iodide (KI) in water and dilute to 1 L.
convenient procedure is to add a small excess of chlorine and
5.7 Sodium Thiosulfate, Standard Solution (0.1 N)—
bring back to the desired titration by addition of some of the
Dissolve 24.8 g of sodium thiosulfate (Na S O ·5H O) in
2 2 3 2
original iodine solution that was taken out at the beginning.
...
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