ASTM_D_5356_-_10_2015.pdf

Designation:D535610(Reapproved 2015)Standard 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 parentheses 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 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 and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2D3898 Test Method for Chromic Oxide in Basic ChromiumTanning LiquorsE70 Test Method for pH of Aqueous Solutions With theGlass Electrode3.Terminology3.1 Definitions 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 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 theappropriate meter.For general details of a procedure,TestMethod E70 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 solution 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 electrodes.The meter shall have a maximum scaledivision of 0.1 pH unit and reproducibility of 0.05 pH unit.NOTE1Sellers list reasonably priced models having more sensitivityand greater reproducibility.7.Reagents7.1 Purity of ReagentsReagent grade 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 ascertained 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 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 pH shall be used formeter standardization,in accordance with the manufacturersrecommendations and the provisions set forth in Test MethodE70.1This 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 Dec.1,2015.Published December 2015.Originallyapproved in 1993.Last previous edition approved in 2010 as D5356 10.DOI:10.1520/D5356-10R15.2For 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 Summary 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 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 States1 8.Standardization8.1 Standardize the meter against the pH 4.00 standard,inaccordance with the manufacturers recommendations and theprovisions set forth in Test Method E70.The buffer standardshall be at room temperature and the temperature compensatorshall be set at this temperature.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 the 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