ASTM D6657-14

Standard Test Method for pH of Wet Blue

SIGNIFICANCE AND USE
4.1 This test method is designed to measure the pH of a distilled-water extract of wet blue. This is considered to be a measure of the acidity or alkalinity of the wet blue. Excessive acidity or alkalinity may have a deleterious effect on the aging characteristics of wet blue and the leather made from it.  
4.2 This test method is suitable for development, control, and service evaluation of wet blue.
SCOPE
1.1 This test method covers the determination of the pH of all types of wet blue and wet white.  
1.2 For pH of wet white, the procedure is identical, substitute wet white for wet blue in the standard method.  
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
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.

General Information

• Status: Historical
• Publication Date: 31-Mar-2014
• ICS: 59.140.10 - Processes and auxiliary materials
• Technical Committee: D31 - Leather
• Drafting Committee: D31.02 - Wet Blue

Relations

• Replaces: ASTM D6657-08 - Standard Test Method for pH of Wet Blue
• Effective Date: 01-Apr-2014
• Replaced By: ASTM D6657-14a - Standard Test Method for pH of Wet Blue
• Effective Date: 01-May-2014

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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.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: D6657 − 14
StandardTest Method for
1
pH of Wet Blue
This standard is issued under the fixed designation D6657; 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 acidity or alkalinity may have a deleterious effect on the aging
characteristics of wet blue and the leather made from it.
1.1 This test method covers the determination of the pH of
all types of wet blue and wet white. 4.2 This test method is suitable for development, control,
and service evaluation of wet blue.
1.2 For pH of wet white, the procedure is identical, substi-
tute wet white for wet blue in the standard method.
5. Apparatus
1.3 The values stated in SI units are to be regarded as
5.1 Electronic pH Meter, with a suitable electrode. The
standard. No other units of measurement are included in this
meter shall have an accuracy of at least 0.01 pH unit and
standard.
reproducibility of 0.05 pH unit.
1.4 This standard does not purport to address all of the
5.2 Analytical Balance, sensitive to 0.01 g or greater.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
6. Reagents
priate safety and health practices and determine the applica-
6.1 Purity of Water—Unless otherwise indicated, references
bility of regulatory limitations prior to use.
to water shall be understood to mean distilled water or water of
2. Referenced Documents
equal purity. Distilled water shall have a pH value of not less
2
than 5.5 nor more than 7.0 and shall give a residue of not more
2.1 ASTM Standards:
than 0.5 mg, when 100 mL is evaporated and dried in a
D6659 Practice for Sampling and Preparation of Wet Blue
platinum dish.
for Physical and Chemical Tests
3
E177 Practice for Use of the Terms Precision and Bias in
6.2 Commercially Standardized pH Solutions :
ASTM Test Methods
6.2.1 Alkaline Phosphate Buffer Solution (0.01 M trisodium
E691 Practice for Conducting an Interlaboratory Study to
phosphate, pH = 11.72 at 25 °C)—Dissolve 1.42 g of anhy-
Determine the Precision of a Test Method
drous disodium hydrogen phosphate (Na HPO ) in 100 mL of
2 4
a 0.1 N carbonate-free solution of sodium hydroxide (NaOH)
3. Terminology
and dilute to 1 L with water.
3.1 Definitions of Term Specific to this Standard:
6.2.2 Borax Buffer Solution (0.01 M, pH = 9.18 at 25
3.1.1 The pH of a solution has been defined as the negative
°C)—Dissolve 3.81 g of sodium tetraborate decahydrate
logarithm of the hydrogen ion activity. A solution of pH 7 is
(Na B O · 10H O) in water and dilute to 1 L.
2 4 7 2
neutral at 24 °C. Lower numbers indicate increasing acidity;
6.2.3 Hydrochloric Acid (pH = 1.10 at 25 °C)—Add2gof
higher numbers, increasing alkalinity.
concentrated hydrochloric acid (HCl, sp gr 1.19) to 450 g of
water. Standardize and dilute to 0.1 N.
4. Significance and Use
6.2.4 Phosphate Buffer Solution (0.025 M with respect to
4.1 This test method is designed to measure the pH of a each phosphate, salt pH = 6.86 at 2.5 °C)—Dissolve 3.40 g of
distilled-water extract of wet blue. This is considered to be a
monobasic potassium phosphate (KH PO ) and 3.55 g of
2 4
measure of the acidity or alkalinity of the wet blue. Excessive anhydrous dibasic sodium phosphate (Na HPO ) in water and
2 4
dilute to 1 L.
6.2.5 Potassium Hydrogen Phthalate Buffer Solution (0.05
1
This test method is under the jurisdiction ofASTM Committee D31 on Leather
M, pH = 4.01 at 25 °C)—Dissolve 10.21 g of potassium
and is the direct responsibility of Subcommittee D31.02 on Wet Blue.
Current edition approved April 1, 2014. Published June 2014. Originally hydrogen phthalate (KHC H O ) in water and dilute to 1 L.
8 4 4
approved in 2001. Last previous edition approved in 2008 as D6657 - 08. DOI:
10.1520/D6657-14.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
3
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Commercial buffer salts and solutions prepared in accordance with National
Standards volume information, refer to the standard’s Document Summary page on Bureau of Standards recommendations are sold by reputable laboratory supply
the ASTM website. houses and may be used.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
D6657 − 14
7. Test Specimen study, testing 16 Wet Blue samples. Every “test result” repre-
sents an individual determination. The laboratories were asked
7.1 The specimen shall consist of 10 g, 6 1 g, from a
to report a single test result for 13
...

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: D6657 − 08 D6657 − 14
Standard Test Method for
1
pH of Wet Blue
This standard is issued under the fixed designation D6657; 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 the pH of all types of wet blue and wet white.
1.2 For pH of wet white, the procedure is identical, substitute wet white for wet blue in the standard method.
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
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.
2. Referenced Documents
2
2.1 ASTM Standards:
D6659 Practice for Sampling and Preparation of Wet Blue for Physical and Chemical Tests
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 of Term Specific to this Standard:
3.1.1 The pH of a solution has been defined as the negative logarithm of the hydrogen ion activity. A solution of pH 7 is neutral
at 24 °C. Lower numbers indicate increasing acidity; higher numbers, increasing alkalinity.
4. Significance and Use
4.1 This test method is designed to measure the pH of a distilled-water extract of wet blue. This is considered to be a measure
of the acidity or alkalinity of the wet blue. Excessive acidity or alkalinity may have a deleterious effect on the aging characteristics
of wet blue and the leather made from it.
4.2 This test method is suitable for development, control, and service evaluation of wet blue.
5. Apparatus
5.1 Electronic pH Meter, with a suitable electrode. The meter shall have an accuracy of at least 0.01 pH unit and reproducibility
of 0.05 pH unit.
5.2 Analytical Balance, sensitive to 0.01 g or greater.
6. Reagents
6.1 Purity of Water—Unless otherwise indicated, references to water shall be understood to mean distilled water or water of
equal purity. Distilled water shall have a pH value of not less than 5.5 nor more than 7.0 and shall give a residue of not more than
0.5 mg, when 100 mL is evaporated and dried in a platinum dish.
3
6.2 Commercially Standardized pH Solutions :
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 Sept. 1, 2008April 1, 2014. Published October 2008June 2014. Originally approved in 2001. Last previous edition approved in 20062008 as
D6657 - 01D6657 - 08.(2006). DOI: 10.1520/D6657-08.10.1520/D6657-14.
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
Commercial buffer salts and solutions prepared in accordance with National Bureau of Standards recommendations are sold by reputable laboratory supply houses and
may be used.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
D6657 − 14
6.2.1 Alkaline Phosphate Buffer Solution (0.01 M trisodium phosphate, pH = 11.72 at 25 °C)—Dissolve 1.42 g of anhydrous
disodium hydrogen phosphate (Na HPO ) in 100 mL of a 0.1 N carbonate-free solution of sodium hydroxide (NaOH) and dilute
2 4
to 1 L with water.
6.2.2 Borax Buffer Solution (0.01 M, pH = 9.18 at 25 °C)—Dissolve 3.81 g of sodium tetraborate decahydrate (Na B O ·
2 4 7
10H O) in water and dilute to 1 L.
2
6.2.3 Hydrochloric Acid (pH = 1.10 at 25 °C)—Add 2 g of concentrated hydrochloric acid (HCl, sp gr 1.19) to 450 g of water.
Standardize and dilute to 0.1 N.
6.2.4 Phosphate Buffer Solution (0.025 M with respect to each phosphate, salt pH = 6.86 at 2.5 °C)—Dissolve 3.40 g of
monobasic potassium phosphate (KH PO ) and 3.55 g of anhydrous dibasic sodium phosphate (Na HPO ) in water and dilute to
2 4 2 4
1 L.
6.2.5 Potassium Hydrogen Phthalate Buffer Solution (0.05 M
...