ASTM D5768-02(2010)
(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 D1959 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 D1541.
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.
1.6 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
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: D5768 − 02 (Reapproved2010)
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
weights, the empirical values obtained are useful for compara-
1.6 This standard does not purport to address all of the
tive purposes.
safety concerns, if any, associated with its use. It is the
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,
iso-octane and cyclohexane. As data on the satisfactory use of
2. Referenced Documents
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 (Withdrawn 2006)
been investigated.
D1959 Test Method for Iodine Value of Drying Oils and
Fatty Acids (Withdrawn 2006)
4. Apparatus
4.1 Bottles—Glass-stopperedbottlesorErlenmeyerflasksof
1 250-mL capacity.
This test method is under the jurisdiction of ASTM Committee D01 on Paint
and Related Coatings, Materials, andApplications and is the direct responsibility of
4.2 Pipets—20 and 25-mL capacity.
Subcommittee D01.34 on Pine Chemicals and Hydrocarbon Resins.
Current edition approved June 1, 2010. Published June 2010. Originally
4.3 Analytical balance
approved in 1995. Last previous edition approved in 2006 as D5768 – 02 (2006).
DOI: 10.1520/D5768-02R10.
5. Reagents
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
5.1 Purity of Reagents—Reagent grade chemicals shall be
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
The last approved version of this historical standard is referenced on
www.astm.org. Specifications of the Committee onAnalytical Reagents of the
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D5768 − 02 (2010)
American Chemical Society, where such specifications are N 5 A 320.39 /C (1)
~ !
available. Other grades may be used provided it is first
where:
ascertained that the reagent is of sufficiently high purity to
A =K Cr O used, g, and
2 2 7
permit its use without lessening the accuracy of the determi-
C =Na S O solution required for titration of the K Cr O ,
2 2 3 2 2 7
nation.
mL.
5.2 Purity of Water—Unless otherwise indicated, references
5.8 Starch Indicator Solution:
to water shall be understood to mean reagent water conforming
5.8.1 Use soluble starch that will pass the following test for
to Type I of Specification D1193.
sensitivity: Make a paste with1gof starch and a small amount
5.3 Acetic Acid (Glacial) 17.4 M—Verify the absence of
of cold water. Add, while stirring, 200 mL of boiling water.
substances reducing permanganate as follows: Dilute 2 mL of
Dilute5mLofthissolutionwith100mLofwaterandadd0.05
the acid with 10 mL of water and add 0.1 mL of 0.1 N
mL of 0.1 N iodine solution. The deep blue color produced
potassium permanganate (KMnO ) solution. The pink color
4 must be discharged by 0.05 mL of 0.1 N Na S O solution.
2 2 3
should not be entirely discharged at the end of 2 h.
5.8.2 Make a homogeneous paste of 10 g of soluble starch
in cold water.Add to this 1 Lof boiling water. Stir rapidly and
5.4 Iso-octane or cyclohexane.
cool. Salicylic acid (1.25 g/L) may be added to preserve the
5.5 Chlorine (99.8 % Cl)—(Warning: Extremely hazard-
indicator. If long storage is required, keep the solution in a
ous. For specific hazard information and guidance, see suppli-
refrigerator at 4 to 10°C (40 to 50°F). Prepare fresh indicator
er’s Material Safety Data sheets.) Commercial grades of
when the end point of the titration from blue to colorless fails
chlorineavailableincylindersmaybeused,providedthegasis
to be sharp.
dried by passing through concentrated sulfuric acid (H SO ,sp
2 4
5.9 Wijs Solution—(Warning: Extremely hazardous. For
gr1.84)beforepassingitintotheiodinesolution.Alternatively,
specific hazard information and guidance, see supplier’s Ma-
the chlorine may be prepared by allowing concentrated hydro-
terial Safety Data sheets.) Dissolve 13.0 g of iodine in 1 L of
chloric acid (HCl, sp gr 1.19) to drop onto potassium perman-
acetic acid. Gentle heat may be necessary to promote solution.
ganate (KMnO ) or onto a mixture of KMnO and manganese
4 4
Cool and remove a small quantity (100 to 200 mL) and set
dioxide (MnO ). Dry the gas thus generated by passing it
aside in a cool place for future use. Pass dry chlorine gas into
through concentrated H SO .
2 4
the iodine solution until the original titration is not quite
5.6 Potassium Iodide Solution (150 g/L)—Dissolve 150 g of
doubled. A characteristic color change takes place in the Wijs
potassium iodide (KI) in water and dilute to 1 L.
solution when the desired amount of chlorine has been added;
5.7 Sodium Thiosulfate, Standard Solution (0.1 N)—
this may be used to assist in judging the end point. A
Dissolve 24.8 g of sodium thiosulfate (Na S O ·5H O) in
2 2 3 2 convenient procedure is to add a small excess of chlorine and
water and dilute to 1 L. Standardize against potassium dichro-
bring back to the desired
...
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