ASTM D6656-01

Standard Test Method for Determination of Chromic Oxide in Wet Blue (Perchloric Acid Oxidation)

SCOPE
1.1 This test method covers the determination of chromic oxide in wet blue that has been partly or completely tanned with chromium compounds. In general, the samples will contain chromium content between 1 % and 5 % when calculated as chromic oxide expressed upon a dry basis otherwise referred to as moisture-free basis (mfb).
1.2 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. See Section for 9 specific safety hazards.

General Information

• Status: Historical
• Publication Date: 09-May-2001
• ICS: 59.140.10 - Processes and auxiliary materials
• ICS: 71.040.40 - Chemical analysis
• Technical Committee: D31 - Leather
• Drafting Committee: D31.02 - Wet Blue

Relations

• Replaced By: ASTM D6656-01(2006) - Standard Test Method for Determination of Chromic Oxide in Wet Blue (Perchloric Acid Oxidation)
• Effective Date: 01-Oct-2006
• Referred By: ASTM D7967-21 - Standard Test Method for Analysis of Chrome Content (as Cr<inf>2</inf>O<inf>3</inf>) in Wet Blue using Atomic Absorption or ICP
• Effective Date: 10-May-2001

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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.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:D6656–01
Standard Test Method for
Determination of Chromic Oxide in Wet Blue (Perchloric
Acid Oxidation)
This standard is issued under the fixed designation D 6656; 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 using released iodine as the titrate. The perchloric acid method
requires less manipulation than procedures based upon fusion
1.1 This test method covers the determination of chromic
of the ash. However, care must be taken because of potential
oxide in wet blue that has been partly or completely tanned
hazards in the use of this reagent.
with chromium compounds. In general, the samples will
contain chromium content between 1 % and 5 % when calcu-
5. Significance and Use
lated as chromic oxide expressed upon a dry basis otherwise
5.1 The procedure described is specific for chromium in wet
referred to as moisture-free basis (mfb).
blue. Vanadium is the only common interfering element and is
1.2 This standard does not purport to address all of the
rarely present in quantity. The precision and accuracy of the
safety concerns, if any, associated with its use. It is the
methods are usually, at least, as good as the sampling of wet
responsibility of the user of this standard to establish appro-
blue itself.
priate safety and health practices and determine the applica-
5.2 The chromium content of wet blue is related to the
bility of regulatory limitations prior to use. See Section 9 for
degree of tannage obtained, and hence may be a matter for
specific safety hazards.
specification in the purchase of wet blue. The procedure
2. Referenced Documents described provides adequate accuracy for this purpose.
2.1 ASTM Standards:
6. Apparatus
D 6658 Test Method for Volatile Matter (Moisture) of Wet
2 6.1 Analytical Balance—accurate and calibrated to 0.001 g.
Blue by Oven Drying
6.2 Erlenmeyer Flasks—250 ml capacity or equivalent.
D 6659 Practice for Sampling and Preparation of Wet Blue
2 6.3 Burette—50 ml capacity of suitable calibration grade,
for Physical and Chemical Tests
minimum calibration of 0.1 ml.
E 180 Practice for Determining the Precision of ASTM
3 6.4 Glass Anti-Bumping Beads—or equivalent.
Methods forAnalysis and Testing of Industrial Chemicals
6.5 Measuring Cylinders—of 50 ml capacity or equivalent.
3. Terminology 6.6 Small Glass Filter Funnel.
6.7 Dessicator—of suitable size and design and charged
3.1 Definitions—The terms and definitions employed within
with fresh dessicant.
this method are commonly used in normal laboratory practice
6.8 Weighing Vessels—of suitable size and design.
and require no special comment.
6.9 Drying Oven—with accurate variable temperature con-
4. Summary of Test Method trols.
4.1 The perchloric acid method may be applied to wet blue.
7. Reagents and Materials
Accuratelyweighedwetbluesamplesaredigestedinablendof
7.1 Purity of Reagents—Analytical Reagent (AR) grade
concentrated nitric acid and a prepared “oxidation mixture”
shall be used in all tests. Unless otherwise indicated, it is
consisting of sulfuric and perchloric acids. Once completed,
intended that all reagents shall conform to specifications of the
oxidation of all tri-valent to haxavalent chrome is executed by
Committee on Analytical Reagents of the American Chemical
controlled heating. Upon dilution, the chromium is indirectly
Society, where such specifications are available. Other grades
(back) titrated volumetrically with standardized thiosulfate
Reagent Chemicals, American Chemical Society Specifications, American
This test method is under the jurisdiction ofASTM Committee D31 on Leather Chemical Society, Washington, DC. For suggestions on the testing of reagents not
and is the direct responsibility of Subcommittee D31.02 on Wet Blue. listed by the American Chemical Society, see Analar Standards for Laboratory
Current edition approved May 10, 2001. Published May 2001. Chemicals, BDH Ltd. Poole, Dorset, UK and the United States Pharmacopoeia and
Annual Book of ASTM Standards, Vol 15.04. National Formulary, U.S. Pharmaceutical Convention, Inc. (USPC), Rockville,
Annual Book of ASTM Standards, Vol 15.05. MD.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D6656
may be used, provided it is first ascertained that the reagent is
B = ml required for titration.
of sufficiently high purity to permit its use without lessening
8.2 Shelf Life—The thiosulfate solution is relatively stable.
the accuracy of the determination.
However, it should be re-standardized at least once every
7.2 Purity of Water—Unless otherwise indicated, reference
month. Alternatively, a commercially available pre-
to water shall be understood to mean distilled water or water of
standardized analytical solution may be substituted.
equal purity.
9. Hazards
7.3 Commercial Reagents—The use of commercially avail-
able pre-standardized analytical reagents and solutions is
9.1 Chemicals used can be harmful and/or explosive.
appropriate, providing those reagents and solutions have been
9.2 The improper use of perchloric acid can lead to violent
prepared according to and conform to the previously men-
and serious explosions. In general, these can be traced to
tioned specifications (see 7.1).
situations where concentrated perchloric acid has come in
7.4 Nitric Acid—(HNO ), 70 % w/w.
contact with organic or easily oxidized materials.
7.5 PerchloricAcid—(HClO ), 60-62 % w/w. 70 % or 72 %
9.3 The exact procedures given must be followed and the
w/w perchloric acid may be substituted; however, storage is digestion, once started, should be kept from possible contact
somewhat more hazardous.
with other organic matter. The digestion should never be
7.6 Sulfuric Acid—(H SO ), 96-98 % w/w. allowed to boil dry. The perchloric acid should never be used
2 4
7.7 Potassium Iodide—(KI), 99-100 % purity. without the accompanying use of nitric and sulfuric acids.
7.8 Potassium Iodide Solution—(KI), 10 % w/w. Dissolve 9.4 Any spills involving perchloric acid should be flushed
10g(6 0.1 g) of potassium iodide into 100 ml of water. with water and a liquid acid neutralizer.
7.9 Starch Indicator Solution—2 % or equivalent. Prepared 9.5 The use of a perchloric acid hood, reserved for perchlo-
according to accepted procedures available in analytical hand- ric acid digestion, equipped with wash-down facilities and
books. constructed entirely of non-porous inorganic material is re-
7.10 Oxidizing Mixture—Mix 1666 ml of concentrated quired.
sulfuric acid into an appropriate glass container that contains 9.6 Perchloric acid bottles should be stored on a ceramic or
2500mlofperchloricacidusingextremecautionwhileadding. non-porous tray or shelf and never on a wooden or pervious
Cool the mixture to room temperature before use. shelf.
7.11 PhosphoricAcid—(H PO ),40 %w/w.Dilute45mlof 9.7 Perchloric acid must not be permitted to go dry in the
3 4
presence of organics, metals or metal salts.
85 % phosphori
...