ASTM D6656-16

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 and health practices and determine the applicability of regulatory limitations prior to use. See Section 9 for specific safety hazards.

General Information

• Status: Historical
• Publication Date: 31-Aug-2016
• ICS: 59.140.10 - Processes and auxiliary materials
• ICS: 71.040.40 - Chemical analysis
• Technical Committee: D31 - Leather
• Drafting Committee: D31.02 - Wet Blue

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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.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 − 16
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.
1. Scope 3. Terminology
1.1 This test method covers the determination of chromic 3.1 Definitions—The terms and definitions employed within
oxide in Wet Blue that has been partly or completely tanned this method are commonly used in normal laboratory practice
with chromium compounds. In general, the samples will and require no special comment.
contain chromium content between 1 % and 5 % when calcu-
lated as chromic oxide expressed upon a dry basis otherwise
4. Summary of Test Method
referred to as moisture-free basis (mfb).
4.1 The perchloric acid method may be applied toWet Blue.
1.2 The values stated in SI units are to be regarded as
Accurately weighed Wet Blue samples are digested in a blend
standard. No other units of measurement are included in this of concentrated nitric acid and a prepared “oxidation mixture”
standard.
consisting of sulfuric and perchloric acids. Once completed,
oxidation of all tri-valent to haxavalent chrome is executed by
1.3 This test method does not apply to Wet White.
controlled heating. Upon dilution, the chromium is indirectly
1.4 This standard does not purport to address all of the
(back) titrated volumetrically with standardized thiosulfate
safety concerns, if any, associated with its use. It is the
using released iodine as the titrate. The perchloric acid method
responsibility of the user of this standard to establish appro-
requires less manipulation than procedures based upon fusion
priate safety and health practices and determine the applica-
of the ash. However, care must be taken because of potential
bility of regulatory limitations prior to use. See Section 9 for
hazards in the use of this reagent.
specific safety hazards.
5. Significance and Use
2. Referenced Documents
2
5.1 TheproceduredescribedisspecificforchromiuminWet
2.1 ASTM Standards:
Blue. Vanadium is the only common interfering element and is
D6658 Test Method for Volatile Matter (Moisture) of Wet
rarely present in quantity. The precision and accuracy of the
Blue by Oven Drying
methods are usually, at least, as good as the sampling of Wet
D6659 Practice for Sampling and Preparation of Wet Blue
Blue itself.
and Wet White for Physical and Chemical Tests
E180 Practice for Determining the Precision of ASTM 5.2 The chromium content of Wet Blue is related to the
Methods for Analysis and Testing of Industrial and Spe-
degree of tannage obtained, and hence may be a matter for
3
cialty Chemicals (Withdrawn 2009) specification in the purchase of Wet Blue. The procedure
E177 Practice for Use of the Terms Precision and Bias in
described provides adequate accuracy for this purpose.
ASTM Test Methods
E691 Practice for Conducting an Interlaboratory Study to
6. Apparatus
Determine the Precision of a Test Method
6.1 Analytical Balance—accurate and calibrated to 0.001 g.
6.2 Erlenmeyer Flasks—250 mL capacity or equivalent.
1
This test method is under the jurisdiction ofASTM Committee D31 on Leather
6.3 Burette—50 mL capacity of suitable calibration grade,
and is the direct responsibility of Subcommittee D31.02 on Wet Blue.
minimum calibration of 0.1 mL.
Current edition approved Sept. 1, 2016. Published October 2016. Originally
approved in 1996. Last previous edition approved in 2014 as D6656 - 14b. DOI:
6.4 Glass Anti-Bumping Beads—or equivalent.
10.1520/D6656-16.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
6.5 Measuring Cylinders—of 50 mLcapacity or equivalent.
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on 6.6 Small Glass Filter Funnel.
the ASTM website.
3
6.7 Dessicator—of suitable size and design and charged
The last approved version of this historical standard is referenced on
www.astm.org. with fresh dessicant.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
D6656 − 16
6.8 Weighing Vessels—of suitable size and design. 7.16 Sodium Thiosulfate Standard Solution—(Na S O ),
2 2 3
0.1N (60.0002). Dissolve 24.85 g of sodium thiosulfate
6.9 Drying Oven—with accurate variable temperature con-
(Na S O ·5H O) in previously boiled water, add 1.00 g of
2 2 3 2
trols.
sodium carbonate (Na CO ) and dilute to 1000 mL.
2 3
7. Reagents and Material
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D6656 − 14b D6656 − 16
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.
1. Scope
1.1 This test method covers the determination of chromic oxide in wet blueWet 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 and health practices and determine the applicability of regulatory
limitations prior to use. See Section 9 for specific safety hazards.
2. Referenced Documents
2
2.1 ASTM Standards:
D6658 Test Method for Volatile Matter (Moisture) of Wet Blue by Oven Drying
D6659 Practice for Sampling and Preparation of Wet Blue and Wet White for Physical and Chemical Tests
E180 Practice for Determining the Precision of ASTM Methods for Analysis and Testing of Industrial and Specialty Chemicals
3
(Withdrawn 2009)
E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
3. Terminology
3.1 Definitions—The terms and definitions employed within this method are commonly used in normal laboratory practice and
require no special comment.
4. Summary of Test Method
4.1 The perchloric acid method may be applied to wet blue.Wet Blue. Accurately weighed wet blueWet Blue samples are
digested in a blend of concentrated nitric acid and a prepared “oxidation mixture” consisting of sulfuric and perchloric acids. Once
completed, oxidation of all tri-valent to haxavalent chrome is executed by controlled heating. Upon dilution, the chromium is
indirectly (back) titrated volumetrically with standardized thiosulfate using released iodine as the titrate. The perchloric acid
method requires less manipulation than procedures based upon fusion of the ash. However, care must be taken because of potential
hazards in the use of this reagent.
5. Significance and Use
5.1 The procedure described is specific for chromium in wet blue.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
blueWet Blue itself.
1
This test method is under the jurisdiction of ASTM Committee D31 on Leather and is the direct responsibility of Subcommittee D31.02 on Wet Blue.
Current edition approved Nov. 1, 2014Sept. 1, 2016. Published December 2014October 2016. Originally approved in 1996. Last previous edition approved in 2014 as
D6656 - 14a.D6656 - 14b. DOI: 10.1520/D6656-14B.10.1520/D6656-16.
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 Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
3
The last approved version of this historical standard is referenced on www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
D6656 − 16
5.2 The chromium content of wet blueWet Blue is related to the degree of tannage obtained, and hence may be a matter for
specification in the purchase of wet blue.Wet Blue. The procedure described provides adequate accuracy for this purpose.
6. Apparatus
6.1 Analytical Balance—accurate and calibrated to 0.001 g.
6.2 Erlenmeyer Flasks—250 mL capacity or equivalent.
6.3 Burette—50 mL capacity of suitable calibration grade, minimum calibration of 0.1 mL.
6.4 Glass Anti-Bumping Beads—or equivalent.
6.5 Measuring Cylinders—of 50 mL capacity or equivalent.
6.6 Small Glass Filter Funnel.
6.7 Dessicator—of suitable size and de
...