1、Designation: D5356 17aStandard Test Method forpH of Chrome Tanning Solutions1This standard is issued under the fixed designation D5356; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parenthe
2、ses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of the pH ofchrome tanning solutions.1.2 The values stated in SI units are to be regarded asstandard. No other
3、units of measurement are included in thisstandard.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety, health, and environmental practices and deter-mine the ap
4、plicability of regulatory limitations prior to use.1.4 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued b
5、y the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D3898 Test Method for Chromic Oxide in Basic ChromiumTanning Liquors3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 pH, of a solutionthe negative logarithm of t
6、hehydrogen ion activity.3.1.1.1 DiscussionA solution of pH 7 is neutral at 24 C.Lower numbers indicate increasing acidity, higher numbersindicate increasing alkalinity.4. Summary of Test Method4.1 The chrome tanning liquor is diluted to a concentrationof 25.0 6 0.5 g chromic oxide equivalent per lit
7、re, allowed tocome to equilibrium and the pH is then measured with theappropriate meter.5. Significance and Use5.1 This test method is designed to measure the pH of achrome tanning solution which has been diluted to a specificconcentration. This is considered to be a measure of the acidityor alkalin
8、ity of the solution.5.2 This test method is suitable for quality control in themanufacture of leather.6. Apparatus6.1 Electronic pH Meter, with a suitable electrode. Themeter shall have an accuracy of at least 0.1 pH unit andreproducibility of 0.05 pH unit.7. Reagents7.1 Purity of ReagentsReagent gr
9、ade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.3Other grades may beused, provided it is first as
10、certained that the reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the determination.7.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean distilled water, deionizedwater, or water of equal purity. Distilled water shall
11、 have a pHvalue of not less than 5.5 nor more than 7.0 and shall give a1This test method is under the jurisdiction of ASTM Committee D31 on Leatherand is the direct responsibility of Subcommittee D31.06 on Chemical AnalysisCurrent edition approved Sept. 1, 2017. Published October 2017. Originallyapp
12、roved in 1993. Last previous edition approved in 2017 as D5356 17. DOI:10.1520/D5356-17A.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summ
13、ary page onthe ASTM website.3Reagent Chemicals, American Chemical Society Specifications , AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and
14、 the United States Pharmacopeiaand National Formulary, U.S. Pharmaceutical Convention, Inc. (USPC), Rockville,MD.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with international
15、ly recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1residue of not more than 0.5 mg when 100 mL is evaporate
16、dand dried in a platinum dish.7.3 Commercially Standardized pH Solutions:47.3.1 Hydrochloric Acid (pH = 1.10 at 25 C)Add2gofconcentrated hydrochloric acid (HCl, sp gr 1.10) to 450 g ofwater. Standardize and dilute to 0.1 N.7.3.2 Potassium Hydrogen Phthalate Buffer Solution (0.05M, pH = 4.01 at 25 C)
17、Dissolve 10.21 g of potassiumhydrogen phthalate (KHC8H4O4) in water and dilute to 1 L.8. Standardization8.1 Use manufacturers directions for establishing two pointstandardization with standard pH solutions that read on eitherside of the anticipated pH of the solution to be tested. Washelectrodes by
18、immersing in three changes of water and estab-lish a fresh liquid junction after blotting electrodes if usingsleeve type electrode prior to testing each solution.8.2 Check for electrode drift with either of the buffers andrestandardize if necessary.9. Procedure9.1 The sample shall be representative
19、of the chrometanning liquor to be tested. It shall be adjusted to an equivalentchromic oxide concentration of 25.0 6 0.5 g/L (Note 1) andallowed to stand at room temperature for at least 60 min beforemeasuring pH in order to attain dilution equilibrium (Note 2).NOTE 1The concentration adjustment sha
20、ll be based on the analysis ofthe liquor for chromium as based on Test Method D3898. In most cases,the concentration of the sample will be above 25 g chromic oxide per litreand measurement of the appropriate quantity of liquor in a graduatedcylinder or weighed quantity shall be transferred to a 100-
21、mL volumetricflask. Diluting with water at room temperature will give sufficientlyaccurate dilution. Spent chrome tanning liquor does not require dilution.NOTE 2If the dilution described in Note 1 takes place essentially atroom temperature, the change in pH is sufficiently slight that 60-minequilibr
22、ation will suffice. If the pH is measured before 60 min has elapsed,report the time. If it is necessary to concentrate the solution by boiling, orthe original solution was hot, then the diluted sample should be allowed toreach room temperature before testing, or the pH test may be repeateduntil cons
23、tant to 0.1 pH are obtained.NOTE 3If measuring the pH of spent chrome tanning solutions, it maybe necessary to remove grease and sediment by filtering prior tomeasurement.9.2 After standardization of the meter (Section 8), rinse theelectrodes three times with water and remove surplus waterwith a sof
24、t, nonabrasive tissue. Do not let the electrodes dry.Immediately immerse the electrodes in the prepared sample toa depth recommended by the manufacturer, set the temperaturecompensator to the temperature of the solution (25 6 5 C),allow the meter to equilibrate, and read the pH to the closest0.05 pH
25、 unit.10. Report10.1 Report the following information:10.1.1 pH of sample = A (25gCr2O3per litre)where:A = pH reading obtained in Section 9 to the nearest 0.05 pHunit.10.1.2 pH of spent chrome tanning liquor = B (undiluted)where:B (undiluted) = pH reading obtained in Section 9 to thenearest 0.05 pH
26、unit.11. Keywords11.1 chrome tanning solutions; pH; spent tanning liquorASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of
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29、eived a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies)
30、of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the Copyright Clearance Center, 222Rosewood Drive, Danvers, MA 01923, Tel: (978) 646-2600; http:/ buffer salts and solutions in accordance with National Bureau ofStandards recommendations are sold by reputable laboratory supply houses and maybe used.D5356 17a2
