ASTM D3898-93(1998)
(Test Method)Standard Test Method for Chromic Oxide in Basic Chromium Tanning Liquors
Standard Test Method for Chromic Oxide in Basic Chromium Tanning Liquors
SCOPE
1.1 This test method covers the determination of chromic oxide in chrome tanning liquors, either simple, with added aluminum or zirconium, or with the usual masking complexing agents.
1.2 This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user of this standard to consult and establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: D 3898 – 93 (Reapproved 1998)
Standard Test Method for
Chromic Oxide in Basic Chromium Tanning Liquors
This standard is issued under the fixed designation D 3898; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope titration, or complex organic or inorganic reducing agents
(sodium thiosulfate, for example) which are not oxidized by
1.1 This test method covers the determination of chromic
alkaline peroxide but reduce hexavalent chromium on acidifi-
oxide in chrome tanning liquors, either simple, with added
cation, an alternate procedure must be used. The perchloric
aluminum or zirconium, or with the usual masking complexing
acid method described in Test Method D 2807, using the
agents.
ferrous sulfate titration, is suitable, although the results ob-
1.2 This standard does not purport to address all of the
tained may be one to two percent low.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
6. Reagents and Materials
priate safety and health practices and determine the applica-
6.1 Purity of Reagents—Reagent grade chemicals shall be
bility of regulatory limitations prior to use.
used in all tests. Unless otherwise indicated, it is intended that
2. Referenced Documents all reagents shall conform to the specifications of the Commit-
tee on Analytical Reagents of The American Chemical Society,
2.1 ASTM Standards:
where such specifications are available. Other grades may be
D 2807 Test Method for Chromic Oxide in Leather (Per-
2 used, provided it is first ascertained that the reagent is of
chloric Acid Oxidation)
sufficiently high purity to permit its use without lessening the
3. Summary of Test Method accuracy of the determination.
6.2 Purity of Water—Unless otherwise indicated, reference
3.1 The solution is oxidized with sodium peroxide until the
to water shall be understood to mean distilled water or water of
chromium is completely converted to the chromate ion. The
equal purity.
solution is boiled to complete oxidation of organic materials
6.3 Sodium Peroxide, (Na O ). Store in original metal can.
2 2
and to destroy excess peroxide; it is then cooled and acidified.
6.4 Starch Indicator, 1 %—Make a paste of1gof soluble
Potassium iodide is added and the liberated iodine is titrated
starch in about 10 mL of water, add 90 mL water and boil for
with standardized sodium thiosulfate.
1 min with stirring. Cool and add 1 drop of chloroform. The
4. Significance and Use
solution is subject to decomposition and should be renewed if
a deep blue color is not obtained on addition of 1 drop of
4.1 The procedure described is for the quality control for
indicator to a solution of 1 drop tincture of iodine in 100 mL
manufacturing liquors and specifications for the purchase of
of water.
such liquors.
6.5 Sodium Thiosulfate Solution, 0.1 N—Dissolve 24.85 g
4.2 The chromium content of the liquors determines the
of Na S O ·5 H O in water, add1gNa CO , and dilute to 1 L.
amount to be used to obtain the desired degree of tannage, and
2 2 3 2 2 3
6.5.1 Standardization—Dry potassium dichromate
hence may be a matter for specification in the purchase of
(K Cr O ) in an oven at 130°C for 2 h and cool in a desiccator.
leather.
2 2 7
Weigh into a glass stoppered Erlenmeyer flask (500 mL) about
5. Interferences
0.2 g of potassium dichromate to an accuracy of 0.1 mg.
Dissolve in 250 mL water, add 15 mL 1:4 hydrochloric acid, 20
5.1 The test method is generally the most accurate and
mL of 10 % potassium iodide solution, stopper the flask and
convenient for the purpose. However, if the liquor contains
allow to stand 5 min in the dark. Titrate with the sodium
iron or copper, which interfere with the sodium thiosulfate
thiosulfate to be standardized. When the color of the solution
This test method is under the jurisdiction of ASTM Committee D-31 on Leather
and is the direct responsibility of Subcommittee D31.06 on Chemical Analysis- Reagent Chemicals, American Chemical Society Specifications, American
General Methods. This test method was developed in cooperation with the American Chemical Society, Washington, DC. For suggestions on the testing of reagents not
Leather Chemists Assoc. listed by the American Chemical Society, see Analar Standards for Laboratory
Current edition approved Jan. 15, 1993. Published March 1993. Originally Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
published as D 3898 – 91. Last previous edition D 3898 – 91. and National Formulary, U.S. Pharmaceutical Convention, Inc. (USPC), R
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.