ASTM D6656-16(2021)

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

SIGNIFICANCE AND USE
5.1 The procedure described is specific for chromium in Wet Blue. Vanadium is the only common interfering element and is rarely present in quantity. The precision and accuracy of the methods are usually, at least, as good as the sampling of Wet Blue itself.  
5.2 The chromium content of Wet Blue is related to the 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.
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 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.3 This test method does not apply to Wet White.  
1.4 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use. See Section 9 for specific safety hazards.  
1.5 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.

General Information

• Status: Published
• Publication Date: 31-Aug-2021
• 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

• Refers: ASTM D6658-08(2020) - Standard Test Method for Volatile Matter (Moisture) of Wet Blue by Oven Drying
• Effective Date: 01-Apr-2020

Standards Content (Sample)

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: D6656 − 16 (Reapproved 2021)
Standard Test Method for
Determination of Chromic Oxide in Wet Blue (Perchloric
1
Acid Oxidation)
This standard is issued under the fixed designation D6656; 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.
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1. Scope cialty Chemicals (Withdrawn 2009)
E177 Practice for Use of the Terms Precision and Bias in
1.1 This test method covers the determination of chromic
ASTM Test Methods
oxide in Wet Blue that has been partly or completely tanned
E691 Practice for Conducting an Interlaboratory Study to
with chromium compounds. In general, the samples will
Determine the Precision of a Test Method
contain chromium content between 1 % and 5 % when calcu-
lated as chromic oxide expressed upon a dry basis otherwise
3. Terminology
referred to as moisture-free basis (mfb).
3.1 Definitions—The terms and definitions employed within
1.2 The values stated in SI units are to be regarded as
this method are commonly used in normal laboratory practice
standard. No other units of measurement are included in this
and require no special comment.
standard.
4. Summary of Test Method
1.3 This test method does not apply to Wet White.
1.4 This standard does not purport to address all of the
4.1 The perchloric acid method may be applied toWet Blue.
safety concerns, if any, associated with its use. It is the Accurately weighed Wet Blue samples are digested in a blend
responsibility of the user of this standard to establish appro-
of concentrated nitric acid and a prepared “oxidation mixture”
priate safety, health, and environmental practices and deter- consisting of sulfuric and perchloric acids. Once completed,
mine the applicability of regulatory limitations prior to use.
oxidation of all tri-valent to haxavalent chrome is executed by
See Section 9 for specific safety hazards. controlled heating. Upon dilution, the chromium is indirectly
1.5 This international standard was developed in accor-
(back) titrated volumetrically with standardized thiosulfate
dance with internationally recognized principles on standard- using released iodine as the titrate. The perchloric acid method
ization established in the Decision on Principles for the requires less manipulation than procedures based upon fusion
Development of International Standards, Guides and Recom-
of the ash. However, care must be taken because of potential
mendations issued by the World Trade Organization Technical hazards in the use of this reagent.
Barriers to Trade (TBT) Committee.
5. Significance and Use
2. Referenced Documents
5.1 TheproceduredescribedisspecificforchromiuminWet
2
Blue. Vanadium is the only common interfering element and is
2.1 ASTM Standards:
rarely present in quantity. The precision and accuracy of the
D6658 Test Method for Volatile Matter (Moisture) of Wet
methods are usually, at least, as good as the sampling of Wet
Blue by Oven Drying
Blue itself.
D6659 Practice for Sampling and Preparation of Wet Blue
and Wet White for Physical and Chemical Tests
5.2 The chromium content of Wet Blue is related to the
E180 Practice for Determining the Precision of ASTM
degree of tannage obtained, and hence may be a matter for
Methods for Analysis and Testing of Industrial and Spe-
specification in the purchase of Wet Blue. The procedure
described provides adequate accuracy for this purpose.
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This test method is under the jurisdiction ofASTM Committee D31 on Leather
6. Apparatus
and is the direct responsibility of Subcommittee D31.02 on Wet Blue.
6.1 Analytical Balance—accurate and calibrated to 0.001 g.
Current edition approved Sept. 1, 2021. Published October 2021. Originally
approved in 1996. Last previous edition approved in 2016 as D6656 - 16. DOI:
6.2 Erlenmeyer Flasks—250 mL capacity or equivalent.
10.1520/D6656-16R21.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
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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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D6656 − 16 (2021)
6.3 Burette—50 mL capacity of suitable calibration grade, 7.12 Hydrochloric Acid—(HCl, 1:1 dilution of 37 %, w/w).
minimum calibration of
...