ASTM D6714-01
(Test Method)Standard Test Method for Chromic Oxide in Ashed Wet Blue (Perchloric Acid Oxidation)
Standard Test Method for Chromic Oxide in Ashed 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 %, calculated as chromic oxide expressed upon a dry basis otherwise referred to as moisture-free basis (mfb).
1.2 This test method is specific in that it applies to a sample or samples that are the resultant ash following the execution of Test Method D 6716.
1.3 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. Specific hazards are given in Section 8.
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Designation:D6714–01
Standard Test Method for
Chromic Oxide in Ashed Wet Blue (Perchloric Acid
Oxidation)
This standard is issued under the fixed designation D 6714; 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 into acidic solution in a blend of nitric acid and a prepared
oxidation mixture consisting of sulfuric and perchloric acids.
1.1 This test method covers the determination of chromic
Once completed, oxidation of all trivalent to hexavalent
oxide in wet blue that has been partly or completely tanned
chromiumisexecutedbycontrolledheating.Upondilution,the
with chromium compounds. In general the samples will con-
chromium is indirectly (back) titrated volumetrically with
tain chromium content between 1 and 5 %, calculated as
standardizedthiosulfateusingreleasediodineasthetitrate.The
chromic oxide expressed upon a dry basis otherwise referred to
perchloric acid method requires less manipulation than proce-
as moisture-free basis (mfb).
dures based on fusion of the ash. However care must be taken
1.2 This test method is specific in that it applies to a sample
because of potential hazards in the use of perchloric acid. The
or samples that are the resultant ash following the execution of
perchloric acid method also tends to give low results.
Test Method D 6716.
1.3 This standard does not purport to address all of the
5. Significance and Use
safety concerns, if any, associated with its use. It is the
5.1 The procedure described is specific for chromium in wet
responsibility of the user of this standard to establish appro-
blue. Vanadium is the only common interfering element and
priate safety and health practices and determine the applica-
this is rarely present in quantity. The precision and accuracy of
bilityofregulatorylimitationspriortouse.Specifichazardsare
the methods are usually at least as good as the sampling of the
given in Section 8.
wet blue itself, and the accuracy of previously performed test
2. Referenced Documents methods.
5.2 The chromium content of wet blue is related to the
2.1 ASTM Standards:
degree of tannage obtained, and hence may be a matter for
D 6658 Test Method for Volatile Matter (Moisture) of Wet
specification in the purchase of wet blue. The procedure
Blue by Oven Drying
described provides adequate accuracy for this purpose.
D 6659 Practice for Sampling and Preparation of Wet Blue
for Physical and Chemical Tests
6. Apparatus
D 6716 Test Method for Total Ash in Wet Blue
6.1 Analytical Balance, accurate and calibrated to 0.001 g.
E 180 Practice for Determining the Precision of ASTM
3 6.2 Erlenmeyer Flasks, 250 mL capacity or equivalent.
Methods forAnalysis and Testing of Industrial Chemicals
6.3 Burette, 50 mL capacity of suitable calibration grade,
3. Terminology minimum calibration of 0.1 mL.
6.4 Glass Anti-bumping Beads, or equivalent.
3.1 Definitions—Thetermsanddefinitionsemployedwithin
6.5 Measuring Cylinders, 50 mL capacity or equivalent.
this test method are commonly used in normal laboratory
6.6 Small Glass Filter Funnel.
practice and require no special comment.
6.7 Dessicator, of suitable size and design and charged with
4. Summary of Test Method fresh dessicant.
6.8 Weighing Vessels, of suitable size and design.
4.1 The perchloric acid method may be applied to the ash
6.9 Drying Oven, with accurate variable temperature con-
obtained inTest Method D 6716.The resultant ash is dissolved
trols.
6.10 Hot Plate, with accurate variable temperature controls.
This test method is under the jurisdiction ofASTM Committee D31 on Leather
and is the direct responsibility of Subcommittee D31.02 on Blue Stock.
Current edition approved Oct. 10, 2001. Published December 2001.
Annual Book of ASTM Standards, Vol 15.04.
Annual Book of ASTM Standards, Vol 15.05.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D6714
7. Reagents the flask, and allow to stand 5 min in the dark. Titrate with the
thiosulfate solution to be standardized. When the color of the
7.1 Purity of Reagents—Analytical Reagent (AR) grade
solutionhasfadedtoabrownish-green,add2mLof2 %starch
chemicals shall be used in all tests. Unless otherwise indicated,
solutionandcontinuetitratinguntilthedeepbluecolorchanges
it is intended that all reagents shall conform to specifications of
toacleargreen.Recordthetitration.Calculatethenormalityof
theCommitteeonAnalyticalReagentsoftheAmericanChemi-
the thiosulfate solution as follows:
cal Society, where such specifications are available. Other
grades may be used, provided it is first ascertained that the Normality 5 A 4 0.04903 3 B
~ !
reagent is of sufficiently high purity to permit its use without
where:
lessening the accuracy of the determination.
A =K Cr O used, g, and
2 2 7
7.2 Purity of Water—Unless otherwise indicated, reference
B = amount required for titration, mL.
to water shall be understood to mean distilled water or water of
7.16.2 Shelf Life—The thiosulfate solution is relatively
equal purity.
stable. However, it should be restandardized at least once a
7.3 Commercial Reagents—The use of commercially avail-
month.
able pre-standardized analytical reagents and solutions is
7.17 Alternatively, a commercially available pre-
appropriate, providing those reagents and solutions have been
standardized sodium thiosulfate analytical solution may be
prepared in accordance with and conforming to the previously
substituted.
mentioned specifications (see 7.1).
7.4 Nitric Acid—(HNO ), 70 % w/w.
8. Hazards
7.5 Perchloric Acid—(HClO ), 60 to 62 % w/w. 70 or 72 %
8.1 Chemicals used can be harmful, or explosive, or both.
w/w perchloric acid may be substituted, however, storage is
8.2 The improper use of perchloric acid can lead to violent
somewhat more hazardous.
and serious explosions. In general, these can be traced to
7.6 Sulfuric Acid—(H SO ), 96 to 98 % w/w.
2 4
situations where concentrated perchloric acid has come in
7.7 Potassium Iodide—(KI), 99 to 100 % purity.
contact with organic or easily oxidized materials.
7.8 Potassium Iodide Solution—(KI) 10 % w/w. Dissolve
8.3 The exact procedures given must be followed and the
10g(60.1 g) of potassium iodide into 100 mL of water.
digestion, once started, should be kept from possible contact
7.9 Starch Indicator Solution—2 % or equivalent, prepared
with other organic matter. The digestion should never be
according to accepted procedures available in analytical hand-
allowed to boil dry. The perchloric acid should never be used
books.
without accompanying use of nitric and sulfuric acids.
7.10 Oxidizing Mixture—Mix 1666 mL of concentrated
8.4 All spills involving perchloric acid should be flushed
sulfuric acid into an appropriate glass container that contains
with water and a liquid acid neutralizer. Rags, sawdust, and
2500 mL of perchloric acid, using extreme caution while
other organic materials should never be used to mop up spilled
adding. Cool the mixture to room temperature before use.
acid.
7.11 Phosphoric Acid—(H PO ), 40 % v/v. Dilute 45 mLof
3 4
8.5 The use of a perchloric acid hood, reserved for perchlo-
85 % phosphoric acid with water to 100 mL.
ric acid digestions, equipped with wash-d
...
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