1、Designation: D 5356 93 (Reapproved 2003)Standard Test Method forpH of Chrome Tanning Solutions1This standard is issued under the fixed designation D 5356; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A
2、 number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) 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 This standard does not purport to address all of t
3、hesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:D 3898 Test Method for Chro
4、mic Oxide in Basic Chro-mium Tanning Liquors2E 70 Test Method for pH of Aqueous Solutions with theGlass Electrode33. Terminology3.1 Definition of Terms Specific to This Standard:3.1.1 pH, of a solutionthe negative logarithm of thehydrogen ion activity.3.1.1.1 DiscussionA solution of pH 7 is neutral
5、at 24C.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 litre, allowed tocome to equilibrium and the pH is then measured with theapp
6、ropriate meter. For general details of a procedure, TestMethod E 70 should be consulted. The provisions of thestandard shall be governing except where the text of this testmethod specifically deviates.5. Significance and Use5.1 This test method is designed to measure the pH of achrome tanning soluti
7、on which has been diluted to a specificconcentration. This is considered to be a measure of the acidityor alkalinity of the solution.5.2 This test method is suitable for quality control in themanufacture of leather.6. Apparatus6.1 pH Meter, either battery or line-operated equipped withappropriate el
8、ectrodes. The meter shall have a maximum scaledivision of 0.1 pH unit and reproducibility of 0.05 pH unit.NOTE 1Sellers list reasonably priced models having more sensitivityand greater reproducibility.7. Reagents7.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwis
9、e 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.4Other grades may beused, provided it is first ascertained that the reagent is ofsufficiently high purity
10、 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 or water ofequal purity.7.3 Buffer SolutionsCommercially available buffer solu-tions of 2.00 6 0.02 pH and 4.00 6 0.02 p
11、H shall be used formeter standardization, in accordance with the manufacturersrecommendations and the provisions set forth in Test MethodE 70.8. Standardization8.1 Standardize the meter against the pH 4.00 standard, inaccordance with the manufacturers recommendations and theprovisions set forth in T
12、est Method E 70. The buffer standardshall be at room temperature and the temperature compensatorshall be set at this temperature.1This test method is under the jurisdiction of ASTM Committee D31 on Leatherand is the direct responsibility of Subcommittee D31.06 on Chemical Analysis.Current edition ap
13、proved May 10, 2003. Published June 2003. Originallyapproved in 1993. Last previous edition approved in 1998 as D 5356 93 (1998).2Annual Book of ASTM Standards, Vol 15.04.3Annual Book of ASTM Standards, Vol 15.05.4Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society,
14、 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 the United States Pharmacopeiaand National Formulary, U.S. Pharmaceutical Convention, Inc. (USPC), Rockville,MD.1Co
15、pyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.8.2 Read the pH of the 2.00 standard with no adjustment ofthe meter. The standard shall be at a temperature no more than2C different from that at which the meter was standardizedagainst th
16、e pH 4.00 standard, and the temperature compensatorset accordingly.8.3 If the reading of the pH 2.00 buffer does not differ bymore than 0.05 pH from the published value under thetemperature conditions, the standardization is satisfactory andthe meter ready for use. If the error exceeds 0.05 pH, the
17、meterand electrodes must be checked and the necessary adjustmentsmade to obtain conformity.9. Procedure9.1 The sample shall be representative 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 2) andallowed to stand at r
18、oom temperature for at least 60 min beforemeasuring pH in order to attain dilution equilibrium (Note 3).NOTE 2The concentration adjustment shall be based on the analysisof the liquor for chromium as based on Test Method D 3898. In mostcases, the concentration of the sample will be above 25 g chromic
19、 oxideper litre and measurement of the appropriate quantity of liquor in agraduate or weighed quantity shall be transferred to a 100-mL volumetricflask. Diluting with water at room temperature, will give sufficientlyaccurate dilution.NOTE 3If the dilution described in Note 2 takes place essentially
20、atroom temperature, the change in pH is sufficiently slight that 60-minequilibration will suffice. If it is necessary to concentrate the solution byboiling, or the original solution was hot, then the diluted sample should beheld at least 24 h before testing, or the pH test may be repeated untilconst
21、ant to 0.1 pH are obtained.9.2 After standardization of the meter (Section 8), rinse theelectrodes three times with water and remove surplus waterwith a soft, nonabrasive tissue. Do not let the electrodes dry.Immediately immerse the electrodes in the prepared sample toa depth recommended by the manu
22、facturer, set the temperaturecompensator to the temperature of the solution (25 6 5C),allow the meter to equilibrate, and read the pH to the nearestpH unit of the meter.10. Report10.1 Report the following information:10.1.1 pH of sample = A (25gCr2O3per litre)where:A = pH reading obtained in Section
23、 8.11. Keywords11.1 chrome tanning solutions; pHASTM 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 any such patent rights,
24、 and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for rev
25、ision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you
26、 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) 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).D 5356 93 (2003)2
