ASTM D6714-16(2021)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D6714 − 16 (Reapproved 2021)
Standard Test Method for
Chromic Oxide in Ashed Wet Blue (Perchloric Acid
Oxidation)
This standard is issued under the fixed designation D6714; 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 and Wet White for Physical and Chemical Tests
D6716 Test Method for TotalAsh in Wet Blue or Wet White
1.1 This test method covers the determination of chromic
E180 Practice for Determining the Precision of ASTM
oxide in Wet Blue that has been partly or completely tanned
Methods for Analysis and Testing of Industrial and Spe-
with chromium compounds. In general the samples will con-
cialty Chemicals (Withdrawn 2009)
tain chromium content between 1 and 5 %, calculated as
chromic oxide expressed upon a dry basis otherwise referred to
3. Terminology
as moisture-free basis (mfb).
3.1 Definitions—The terms and definitions employed within
1.2 This test method is specific in that it applies to a sample
this test method are commonly used in normal laboratory
or samples that are the resultant ash following the execution of
practice and require no special comment.
Test Method D6716.
4. Summary of Test Method
1.3 This test method does not apply to Wet White.
4.1 The perchloric acid method may be applied to the ash
1.4 The values stated in SI units are to be regarded as
obtained in Test Method D6716. The resultant ash is dissolved
standard. No other units of measurement are included in this
into acidic solution in a blend of nitric acid and a prepared
standard.
oxidation mixture consisting of sulfuric and perchloric acids.
1.5 This standard does not purport to address all of the
Once completed, oxidation of all trivalent to hexavalent
safety concerns, if any, associated with its use. It is the
chromiumisexecutedbycontrolledheating.Upondilution,the
responsibility of the user of this standard to establish appro-
chromium is indirectly (back) titrated volumetrically with
priate safety, health, and environmental practices and deter-
standardizedthiosulfateusingreleasediodineasthetitrate.The
mine the applicability of regulatory limitations prior to use.
perchloric acid method requires less manipulation than proce-
Specific hazards are given in Section 8.
dures based on fusion of the ash. However care must be taken
1.6 This international standard was developed in accor-
because of potential hazards in the use of perchloric acid. The
dance with internationally recognized principles on standard-
perchloric acid method also tends to give low results.
ization established in the Decision on Principles for the
5. Significance and Use
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical 5.1 TheproceduredescribedisspecificforchromiuminWet
Blue. Vanadium is the only common interfering element and
Barriers to Trade (TBT) Committee.
this is rarely present in quantity. The precision and accuracy of
2. Referenced Documents
the methods are usually at least as good as the sampling of the
Wet Blue itself, and the accuracy of previously performed test
2.1 ASTM Standards:
methods.
D6658 Test Method for Volatile Matter (Moisture) of Wet
Blue by Oven Drying
5.2 The chromium content of Wet Blue is related to the
D6659 Practice for Sampling and Preparation of Wet Blue
degree of tannage obtained, and hence may be a matter for
specification in the purchase of Wet Blue. The procedure
described provides adequate accuracy for this purpose.
This test method is under the jurisdiction ofASTM Committee D31 on Leather
and is the direct responsibility of Subcommittee D31.02 on Wet Blue.
6. Apparatus
Current edition approved Sept. 1, 2021. Published October 2021. Originally
6.1 Analytical Balance, accurate and calibrated to 0.001 g.
approved in 2001. Last previous edition approved in 2016 as D6714 - 16. DOI:
10.1520/D6714-16R21.
6.2 Erlenmeyer Flasks, 250 mL capacity or equivalent.
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
Standards volume information, refer to the standard’s Document Summary page on The last approved version of this historical standard is referenced on
the ASTM website. www.astm.org.
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D6714 − 16 (2021)
6.3 Burette, 50 mL capacity of suitable calibration grade, 7.11 Phosphoric Acid—(H PO ), 40 % v/v. Dilute 45 mLof
3 4
minimum calibration of 0.1 mL. 85 % phosphoric acid with water to 100 mL.
6.4 Glass Anti-bumping Beads, or equivalent.
7.12 Hydrochloric Acid—(HCl), 1:1 dilution of 37 % HCl
w/w. Used in standardization of thiosulfate solution.
6.5 Measuring Cylinders, 50 mL capacity or equivalent.
6.6 Small Glass Filter Funnel. 7.13 Potassium Dichromate—(K Cr O ). Used in standard-
2 2 7
ization of thiosulfate solution.
6.7 Dessicator, of suitable size and design and charged with
fresh dessicant.
7.14 Sodium Carbonate—(Na CO ). Used in preparation of
2 3
thiosulfate solution.
6.8 Weighing Vessels, of suitable size and design.
6.9 Drying Oven, with accurate variable temperature con- 7.15 Sodium Thiosulfate—(Na S O ·5H O). Used to pre-
2 2 3 2
pare thiosulfate solution.
trols.
6.10 Hot Plate, with accurate variable temperature controls.
7.16 Sodium Thiosulfate Standard Solution—(Na S O ),
2 2 3
0.1N (60.0002). Dissolve 24.85 g of sodium thiosulfate
6.11 Perchloric Acid Hood .
(Na S O ·5H O) in previously boiled water, add 1.00 g of
2 2 3 2
sodium carbonate (Na CO ) and dilute to 1000 mL.
2 3
7. Reagents
7.16.1 Standardization—Dry potassium dichromate
7.1 Purity of Reagents—Analytical Reagent (AR) grade
(K Cr O ) in an oven at 130°C for 2 h and cool in a dessicator.
2 2 7
chemicals shall be used in all tests. Unless otherwise indicated,
Once cool, weigh about 0.2 g (60.0001 g) of this dry
it is intended that all reagents shall conform to specifications of
potassium dichromate into a clean 250 mL, glass-stoppered
theCommitteeonAnalyticalReagentsoftheAmericanChemi-
Erlenmeyer flask. Dissolve in 50 mL of water; add 4 mL of
cal Society, where such specifications are available. Other
hydrochloricacid(HCl,1:1)and20mLofKIsolution.Stopper
grades may be used, provided it is first ascertained that the
the flask, and allow to stand 5 min in the dark. Titrate with the
reagent is of sufficiently high purity to permit its use without
thiosulfate solution to be standardized. When the color of the
lessening the accuracy of the determination.
solutionhasfadedtoabrownish-green,add2mLof2 %starch
7.2 Purity of Water—Unless otherwise indicated, reference
solutionandcontinuetitratinguntilthedeepbluecolorchanges
to water shall be understood to mean distilled water, deionized
toacleargreen.Recordthetitration.Calculatethenormalityof
water, or water of equal purity.
the thiosulfate solution as follows:
7.3 Commercial Reagents—The use of commercially avail-
Normality 5 A÷~0.04903 3B!
able pre-standardized analytical reagents and solutions is
where:
appropriate, providing those reagents and solutions have been
A =K Cr O used, g, and
prepared in accordance with and conforming to the previously 2 2 7
B = amount required for titration, mL.
mentioned specifications (see 7.1).
7.16.2 Shelf Life—The thiosulfate solution is relatively
7.4 Nitric Acid—(HNO ), 70 % w/w.
stable. However, it should be restandardized at least once a
7.5 Perchloric Acid—(HClO ), 60 to 62 % w/w. 70 or 72 %
month.
w/w perchloric acid may be substituted, however, storage is
somewhat more hazardous.
7.17 Alternatively, a commercially available pre-
standardized sodium thiosulfate analytical solution may be
7.6 Sulfuric Acid—(H SO ), 96 to 98 % w/w.
2 4
substituted.
7.7 Potassium Iodide—(KI), 99 to 100 % purity.
7.8 PotassiumIodideSolution—
...