ASTM D6019-20

Test Method for Determination of Chromic Oxide in Basic Chromium Tanning Liquors (Ammonium Persulfate Oxidation)

SIGNIFICANCE AND USE
4.1 The procedure described is for the quality control for manufacturing liquors and specifications for the purchase of such liquors.  
4.2 The chromium content of the liquors determines the amount to be used to obtain the desired degree of tannage, and hence may be a matter for specification in the purchase of leather.
SCOPE
1.1 This test method covers the determination of chromic oxide in chrome tanning liquors, either simple, with added aluminum or zirconium, or with the usual masking complexing agents.  
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 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.  
1.4 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-Mar-2020
• ICS: 59.140.10 - Processes and auxiliary materials
• ICS: 71.040.40 - Chemical analysis
• Technical Committee: D31 - Leather
• Drafting Committee: D31.06 - Chemical Analysis

Relations

• Replaces: ASTM D6019-15 - Test Method for Determination of Chromic Oxide in Basic Chromium Tanning Liquors (Ammonium Persulfate Oxidation)
• Effective Date: 01-Apr-2020
• Referred By: ASTM D3897-18 - Standard Test Method for Calculation of Basicity of Chrome Tanning Liquors
• Effective Date: 01-Apr-2020

Overview

ASTM D6019-20 is a standardized test method developed by ASTM International for the determination of chromic oxide in basic chromium tanning liquors using ammonium persulfate oxidation. The accurate measurement of chromic oxide content is crucial for both the quality control of tanning liquors during leather manufacturing and in specifying purchase requirements for these liquors. This standard ensures consistency and reliability across the leather industry by providing a clear procedure for chromic oxide determination.

Key Topics

• Chromic Oxide Analysis: Focuses on the precise determination of chromic oxide concentration in both simple tanning liquors and those with additives such as aluminum, zirconium, or complexing agents.
• Ammonium Persulfate Oxidation Method: Outlines an oxidation and titration technique where chromium is converted to chromate ion using ammonium persulfate, followed by iodometric titration with sodium thiosulfate.
• Quality Assurance: Supports consistent quality control processes for manufacturers and buyers by standardizing chromic oxide measurement.
• Reproducibility and Precision: The method's design ensures high repeatability within laboratories and reliable reproducibility across different facilities.
• Safety and Compliance: Provides guidance on safe laboratory practices, requiring users to establish appropriate safety and environmental procedures relevant to their regulatory environment.

Applications

The ASTM D6019-20 standard is vital for several key applications in the leather and tanning industry:

• Quality Control During Leather Production: Enables tanneries to monitor and adjust the chromium content in tanning solutions, ensuring optimal tanning results and meeting product specifications.
• Specification for Procurement: Assists purchasers in verifying the chromic oxide content of supplied tanning liquors, facilitating transparent transactions and adherence to required standards.
• Recycled Chrome Monitoring: Applies to recycled or reacidified chrome liquors, supporting sustainable leather processing by monitoring recycled material quality.
• Research and Development: Serves as a reference method in the development of new tanning processes or formulations involving basic chromium salts.
• Regulatory Compliance: Helps production facilities meet local and international standards regarding the composition of chemicals used in leather tanning processes.

Related Standards

Organizations frequently reference ASTM D6019-20 alongside other important standards in leather, chemical, and analytical quality control, such as:

• ASTM D28 (General Standards for Leather) - Provides definitions and additional test methods pertaining to leather manufacture.
• ASTM D31 (Leather Committee Standards) - Encompasses test methods and practices for chemical analysis of leathers.
• ISO 17025 (Testing and Calibration Laboratories) - Specifies quality and competence requirements for laboratories performing such chemical tests.
• ASTM E200 (Standard Practice for Preparation, Standardization, and Storage of Standard and Reagent Solutions) - Facilitates reagent preparation and handling longevity.

Practical Value

Implementing ASTM D6019-20 strengthens a company's commitment to quality, sustainability, and regulatory compliance. By following a standardized protocol for chromic oxide determination:

• Manufacturers gain reliable data for process control and product quality.
• Buyers receive assurance on the integrity and consistency of tanning liquors.
• Laboratories execute precise and repeatable analyses, fostering customer confidence.
• Industry Stakeholders benefit from harmonized practices that support global trade and technical collaboration.

Overall, the adoption of ASTM D6019-20 enhances the efficiency, safety, and integrity of leather tanning operations worldwide.

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: D6019 − 20
Test Method for
Determination of Chromic Oxide in Basic Chromium
Tanning Liquors (Ammonium Persulfate Oxidation)
This standard is issued under the fixed designation D6019; 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 4. Significance and Use
1.1 This test method covers the determination of chromic 4.1 The procedure described is for the quality control for
oxide in chrome tanning liquors, either simple, with added manufacturing liquors and specifications for the purchase of
aluminum or zirconium, or with the usual masking complexing such liquors.
agents.
4.2 The chromium content of the liquors determines the
1.2 The values stated in SI units are to be regarded as amount to be used to obtain the desired degree of tannage, and
standard. No other units of measurement are included in this hence may be a matter for specification in the purchase of
standard. leather.
1.3 This standard does not purport to address all of the
5. Reagents and Materials
safety concerns, if any, associated with its use. It is the
5.1 Purity of Reagents—Reagent grade chemicals shall be
responsibility of the user of this standard to establish appro-
used in all tests. Unless otherwise indicated, it is intended that
priate safety, health, and environmental practices and deter-
all reagents shall conform to the specifications of the Commit-
mine the applicability of regulatory limitations prior to use.
tee onAnalytical Reagents ofTheAmerican Chemical Society,
1.4 This international standard was developed in accor-
where such specifications are available. Other grades may be
dance with internationally recognized principles on standard-
used, provided it is first ascertained that the reagent is of
ization established in the Decision on Principles for the
sufficiently high purity to permit its use without lessening the
Development of International Standards, Guides and Recom-
accuracy of the determination.
mendations issued by the World Trade Organization Technical
5.2 Purity of Water—Unless otherwise indicated, reference
Barriers to Trade (TBT) Committee.
to water shall be understood to mean distilled water, deionized
2. Summary of Test Method water or water of equal purity.
2.1 The solution is oxidized with ammonium persulfate 5.3 Ammonium Persulfate—20 % solution 100 g of persul-
until the chromium is completely converted to the chromate fate into 500 mL water.
ion. The solution is boiled to complete oxidation of organic 5.3.1 Alternatively, ammonium persulfate may be added in
materialsandtodestroyexcessammoniumpersulfate;itisthen 6.6 as solid form using plastic scoopula.
cooled and acidified. Potassium iodide is added, and the
5.4 Starch Indicator,2%—Make a paste of2gof soluble
liberated iodine is titrated with standardized sodium thiosul-
starch in about 10 mL of water, add 90 mL water, and boil for
fate.
1 min with stirring. Cool. Refrigerate after use. The solution is
subject to decomposition and should be renewed if a deep blue
3. Terminology
color is not obtained on addition of one drop of indicator to a
3.1 Definitions: solution of 1 drop tincture of iodine in 100 mL of water.
3.1.1 recycled chrome (reacidified chrome), n—the mixture
5.5 Sodium Thiosulfate Solution, 0.1 N—Dissolve 24.85 g
obtained when spent chrome liquor is captured, filtered,
of Na S O ·5H O in water, add1gNa CO , and dilute to 1 L.
2 2 3 2 2 3
precipitated with alkali and the precipitate is reacidified with
5.5.1 Standardization—Dry potassium dichromate
sulfuric acid.
(K Cr O ) in an oven at 130°C for 2 h and cool in a desiccator.
2 2 7
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 D31.06 on Chemical Analysis. listed by the American Chemical Society, see Analar Standards for Laboratory
Current edition approved April 1, 2020. Published May 2020. Originally Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
approved in 1996. Last previous edition approved in 2015 as D6019 – 15. DOI: and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,
10.1520/D6019-20. MD.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6019 − 20
Weigh into a glass stoppered Erlenmeyer flask (500 mL) about 6.5.2 Dilute to the 250 mL mark of the flask with water.
0.2 g of potassium dichromate to an accuracy of 0.1 mg. Then proceed to step 6.6.
Dissolvein250mLwater,add15mL1:4hydrochloricacid,20
6.6 Add the following chemicals:
mL of 10 % potassium iodide solution, stopper the flask, and
50 mL of 20 % ammonium persulfate solution or 10 g of
allow to stand 5 min in the dark. Titrate with the sodium
ammonium persulfate
thiosulfate to be standardized. When the color of the solution
8 mL of 1 % silver nitrate solution
has faded to a brownish-green, add 2 mL of 2 % starch
1 mL of 1 % potassium permanganate solution
solution, and continue titrating until the deep blue color
6.7 Bringtoaboil.Atthisstage,apermanganatecolor(dark
changes to a clear green. Record the titration.
red;red-brown)shoulddevelop.Ifthepermanganatecolorfails
weight potassium dichromate
to develop, or fades on boiling, remove the flask from the hot
normality of sodium thiosulfate 5 (1)
0.04903 3mL titration
plate. Cool slightly, then carefully add 5-10 mL of additional
20 % ammonium persulfate solution or 1-2 g additional
The thiosulfate solution is quite stable but should be restan-
ammonium persulfate. Swirl to mix. If necessary, continue
dardized at least once a month.
addition of ammonium persulfate (5-10 mL of 20 % ammo-
5.6 Potassium Dichromate, K Cr O , primary standard
2 2 7
nium persulfate solution or 1-2 g of ammonium persulfate, at a
grade.
time) until the per
...

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: D6019 − 15 D6019 − 20
Test Method for
Determination of Chromic Oxide in Basic Chromium
Tanning Liquors (Ammonium Persulfate Oxidation)
This standard is issued under the fixed designation D6019; 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 chrome tanning liquors, either simple, with added aluminum
or zirconium, or with the usual masking complexing agents.
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 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.4 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.
2. Summary of Test Method
2.1 The solution is oxidized with ammonium persulfate until the chromium is completely converted to the chromate ion. The
solution is boiled to complete oxidation of organic materials and to destroy excess ammonium persulfate; it is then cooled and
acidified. Potassium iodide is added, and the liberated iodine is titrated with standardized sodium thiosulfate.
3. Terminology
3.1 Definitions:
3.1.1 recycled chrome (reacidified chrome), n—the mixture obtained when spent chrome liquor is captured, filtered, precipitated
with alkali and the precipitate is reacidified with sulfuric acid.
4. Significance and Use
4.1 The procedure described is for the quality control for manufacturing liquors and specifications for the purchase of such
liquors.
4.2 The chromium content of the liquors determines the amount to be used to obtain the desired degree of tannage, and hence
may be a matter for specification in the purchase of leather.
5. Reagents and Materials
5.1 Purity of Reagents—Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that all
reagents shall conform to the specifications of the Committee on Analytical Reagents of The American Chemical Society, where
such specifications are available. Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high
purity to permit its use without lessening the accuracy of the determination.
5.2 Purity of Water—Unless otherwise indicated, reference to water shall be understood to mean distilled water, deionized water
or water of equal purity.
5.3 Ammonium Persulfate—20 % solution 100 g of persulfate into 500 mL water.
This test method is under the jurisdiction of ASTM Committee D31 on Leather and is the direct responsibility of Subcommittee D31.06 on Chemical Analysis.
Current edition approved Dec. 1, 2015April 1, 2020. Published January 2016May 2020. Originally approved in 1996. Last previous edition approved in 20102015 as
D6019 – 10.D6019 – 15. DOI: 10.1520/D6019-15.10.1520/D6019-20.
Reagent Chemicals, American Chemical Society Specifications , American Chemical Society, Washington, DC. For suggestions on the testing of reagents not listed by
the American Chemical Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia and National
Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville, MD.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6019 − 20
5.3.1 Alternatively, ammonium persulfate may be added in 5.56.6 as solid form using plastic scoopula.
5.4 Starch Indicator, 2 %—Make a paste of 2 g of soluble starch in about 10 mL of water, add 90 mL water, and boil for 1 min
with stirring. Cool. Refrigerate after use. The solution is subject to decomposition and should be renewed if a deep blue color is
not obtained on addition of one drop of indicator to a solution of 1 drop tincture of iodine in 100 mL of water.
5.5 Sodium Thiosulfate Solution, 0.1 N—Dissolve 24.85 g of Na S O ·5H O in water, add 1 g Na CO , and dilute to 1 L.
2 2 3 2 2 3
5.5.1 Standardization—Dry potassium dichromate (K Cr O ) in an oven at 130°C for 2 h and cool in a desiccator. Weigh into
2 2 7
a glass stoppered Erlenmeyer flask (500 mL) about 0.2 g of potassium dichromate to an accuracy of 0.1 mg. Dissolve in 250 mL
water, add 15 mL 1:4 hydrochloric acid, 20 mL of 10 % potassium iodide solution, stopper the flask, and allow to stand 5 min in
the dark. Titrate with the sodium thiosulfate to be standardized. When the color of the solution has faded to a brownish-green, add
2 mL of 2 % starch solution, and continue titrating until the deep blue color changes to a clear green. Record the titration.
weight potassium dichromate
normality of sodium thiosulfate 5 (1)
0.04903 3mL titration
The thiosulfate solution is quite stable but should be restandardized at least once a month.
5.6 Potassium Dichromate, K Cr O , primary standard grade.
2 2 7
5.7 Potassium Iodide, 10 %—Dissolve 10 g KI in 100 mL water.
5.8 Hydrochloric Acidacid, 1:1—Dilute 250 mL concentrated hydrochloric acid (sp gr 1.19) in 250 mL water.
5.9 Silver Nitrate, 1 %—Dissolve 1 g of AgNO in 100 mL water.
5.10 Potassium Permanganate, 1 %—Dissolve 1 g of KMnO in 100 mL water.
5.11 Sulfuric acid, concentrated.
5.12 Nitric acid, concentrated.
6. Procedure
6.1 Weigh 11 to 12 g, to the nearest 0.1 mg, of the chrome tanning material to be analyzed. Record weight.
6.2 Quantitatively transfer to a 500 mL volumetric flask. Dilute to the mark and mix thoroughly.
6.3 Pipet 25 mL aliquots into each of 500 mL Erlenmeyer flasks. Add boiling chips or glass beads. Run in triplicate.
NOTE 1—Proceed with step 6.4 (commercially-available chrome tanning liquor) or step 6.5 (recycled chrome) as applicable.
6.4 Commercially-available chrome tanning liquor—Dilute to the 200250 mL mark of the flask with water.
6.4.1 Add 10 mL concentrated sulfuric acid. (Warning—This should be done in a hood. Heat and fumes will be generated).
6.4.2 Proceed to step 6.6.
6.5 Recycled chrome digestion—(Warning—This digestion should be done in a hood. Heat and fumes will be generated). Add
20 mL concentrated nitric acid, then 10 mL concentrated sulfuric acid.
6.5.1 Digest the mixture on the hot plate until the flask fills with dense white fumes and the solution is emerald (rich green)
in color. (T
...