ASTM_D_5356_-_17a.pdf

Designation:D535617aStandard 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,health,and environmental practices and deter-mine the applicability 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 by 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 thehydrogen 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 litre,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 alkalinity 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 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,deionizedwater,or water of equal purity.Distilled water shall 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.Originallyapproved 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 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 StatesThis international standard was developed in accordance with internationally 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.1 residue of not more than 0.5 mg when 100 mL is evaporatedand dried in a platinum dish.7.3 Commercially Standardized pH Solutions:47.3.1 Hydrochloric Acid(pH=1.10 at 25 C)Add 2 g ofconcentrated 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)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.Was