ASTM D5356-93(1998)

NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
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Designation: D 5356 – 93 (Reapproved 1998)
Standard Test Method for
pH of Chrome Tanning Solutions
This standard is issued under the fixed designation D 5356; 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 concentration. This is considered to be a measure of the acidity
or alkalinity of the solution.
1.1 This test method covers the determination of the pH of
5.2 This test method is suitable for quality control in the
chrome tanning solutions.
manufacture of leather.
1.2 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
6. Apparatus
responsibility of the user of this standard to establish appro-
6.1 pH Meter, either battery or line-operated equipped with
priate safety and health practices and determine the applica-
appropriate electrodes. The meter shall have a maximum scale
bility of regulatory limitations prior to use.
division of 0.1 pH unit and reproducibility of 0.05 pH unit.
2. Referenced Documents
NOTE 1—Sellers list reasonably priced models having more sensitivity
2.1 ASTM Standards:
and greater reproducibility.
D 3898 Test Method for Chromium in Basic Chromium
2 7. Reagents
Tanning Liquors
7.1 Purity of Reagents—Reagent grade chemicals shall be
E 70 Test Method for pH of Aqueous Solutions with the
Glass Electrode used in all tests. Unless otherwise indicated, it is intended that
all reagents shall conform to the specifications of the Commit-
3. Terminology
tee on Analytical Reagents of the American Chemical Society,
3.1 Definition of Term Specific to This Standard: where such specifications are available. Other grades may be
3.1.1 pH, of a solution—the negative logarithm of the used, provided it is first ascertained that the reagent is of
hydrogen ion activity. sufficiently high purity to permit its use without lessening the
3.1.1.1 Discussion—A solution of pH 7 is neutral at 24°C. accuracy of the determination.
Lower numbers indicate increasing acidity, higher numbers 7.2 Purity of Water—Unless otherwise indicated, references
indicate increasing alkalinity. to water shall be understood to mean distilled water or water of
equal purity.
4. Summary of Test Method
7.3 Buffer Solutions—Commercially available buffer solu-
4.1 The chrome tanning liquor is diluted to a concentration tions of 2.00 6 0.02 pH and 4.00 6 0.02 pH shall be used for
of 25.0 6 0.5 g chromic oxide equivalent per litre, allowed to meter standardization, in accordance with the manufacturer’s
come to equilibrium and the pH is then measured with the
recommendations and the provisions set forth in Test Method
appropriate meter. For general details of a procedure, Test E 70.
Method E 70 should be consulted. The provisions of the
8. Standardization
standard shall be governing except where the text of this test
method specifically deviates. 8.1 Standardize the meter against the pH 4.00 standard, in
accordance with the manufacturer’s recommendations and the
5. Significance and Use
provisions set forth in Test Method E 70. The buffer standard
5.1 This test method is designed to measure the pH of a
shall be at room temperature and the temperature compensator
chrome tanning solution which has been diluted to a specific shall be set at this temperature.
1 4
This test method is under the jurisdiction of ASTM Committee D-31 on Leather Reagent Chemicals, American Chemical Society Specifications, American
and is the direct responsibility of Subcommittee D31.06 on Chemical Analysis— Chemical Society, Washington, DC. For suggestions on the testing of reagents not
General Methods. listed by the American Chemical Society, see Analar Standards for Laboratory
Current edition approved Jan. 15, 1993. Published March 1993. Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
Annual Book of ASTM Standards, Vol 15.04. and Nati
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