ASTM D6657-01(2006)

Standard Test Method for pH of Wet Blue

SIGNIFICANCE AND USE
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.
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.
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: 30-Sep-2006
• ICS: 59.140.10 - Processes and auxiliary materials
• Technical Committee: D31 - Leather
• Drafting Committee: D31.02 - Wet Blue

Relations

• Replaces: ASTM D6657-01 - Standard Test Method for pH of Wet Blue
• Effective Date: 01-Oct-2006
• Replaced By: ASTM D6657-08 - Standard Test Method for pH of Wet Blue
• Effective Date: 01-Sep-2008

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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.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:D6657–01(Reapproved 2006)
Standard Test Method for
pH of Wet Blue
This standard is issued under the fixed designation D 6657; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope 6. Reagents
1.1 This test method covers the determination of the pH of 6.1 Purity of Water—Unless otherwise indicated, references
all types of wet blue. to water shall be understood to mean distilled water or water of
1.2 This standard does not purport to address all of the equal purity. Distilled water shall have a pH value of not less
safety concerns, if any, associated with its use. It is the than 5.5 nor more than 7.0 and shall give a residue of not more
responsibility of the user of this standard to establish appro- than 0.5 mg, when 100 mL is evaporated and dried in a
priate safety and health practices and determine the applica- platinum dish.
bility of regulatory limitations prior to use. 6.2 Commercially Standardized pH Solutions :
6.2.1 Alkaline Phosphate Buffer Solution (0.01 M trisodium
2. Referenced Documents
phosphate, pH = 11.72 at 25 °C)—Dissolve 1.42 g of anhy-
2.1 ASTM Standards:
drous disodium hydrogen phosphate (Na HPO ) in 100 mL of
2 4
D 6659 Practice for Sampling and Preparation of Wet Blue a 0.1 N carbonate-free solution of sodium hydroxide (NaOH)
for Physical and Chemical Tests
and dilute to 1 L with water.
6.2.2 Borax Buffer Solution (0.01 M, pH = 9.18 at 25
3. Terminology
°C)—Dissolve 3.81 g of sodium tetraborate decahydrate
3.1 Definitions of Term Specific to this Standard:
(Na B O · 10H O) in water and dilute to 1 L.
2 4 7 2
3.1.1 The pH of a solution has been defined as the negative
6.2.3 Hydrochloric Acid (pH = 1.10 at 25 °C)—Add2gof
logarithm of the hydrogen ion activity. A solution of pH 7 is
concentrated hydrochloric acid (HCl, sp gr 1.19) to 450 g of
neutral at 24 °C. Lower numbers indicate increasing acidity;
water. Standardize and dilute to 0.1 N.
higher numbers, increasing alkalinity.
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
4. Significance and Use
monobasic potassium phosphate (KH PO ) and 3.55 g of
2 4
4.1 This test method is designed to measure the pH of a
anhydrous dibasic sodium phosphate (Na HPO ) in water and
2 4
distilled-water extract of wet blue. This is considered to be a
dilute to 1 L.
measure of the acidity or alkalinity of the wet blue. Excessive
6.2.5 Potassium Hydrogen Phthalate Buffer Solution (0.05
acidity or alkalinity may have a deleterious effect on the aging
M, pH = 4.01 at 25 °C)—Dissolve 10.21 g of potassium
characteristics of wet blue and the leather made from it.
hydrogen phthalate (KHC H O ) in water and dilute to 1 L.
8 4 4
4.2 This test method is suitable for development, control,
7. Test Specimen
and service evaluation of wet blue.
7.1 The specimen shall consist of 10 g, 6 1 g, from a
5. Apparatus
composite sample prepared according to Practice D 6659.
5.1 Electronic pH Meter, with a suitable electrode. The
8. Standardization
meter shall have an accuracy of at least 0.01 pH unit and
reproducibility of 0.05 pH unit.
8.1 Use manufacturer’s directions for establishing two point
5.2 Analytical Balance, sensitive to 0.01 g or greater.
standardization with standard pH solutions that read on either
side of the anticipated pH of the solution to be tested. Wash
electrodes by immersing in three changes of water and estab-
This test method is under the jurisdiction ofASTM Committee D31 on Leather
lish a fresh liquid junction after blotting electrodes if using
and is the direct responsibility of Subcommittee D31.02 on Blue Stock.
sleeve type electrode prior to testing each solution.
Current edition approved O
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