ASTM_D_2810_-_18.pdf

Designation:D281018Standard Test Method forpH of Leather1This standard is issued under the fixed designation D2810;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.This standard has been approved for use by agencies of the U.S.Department of Defense.1.Scope1.1 This test method covers the determination of the pH ofall types of leather.This method does not apply to wet blue orwet white.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:D2813 Practice for Sampling Leather for Physical andChemical Tests3.Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 The pH of a solution has been defined as the negativelogarithm of the hydrogen ion activity.A solution of pH 7 isneutral at 24C.Lower numbers indicate increasing acidity;higher numbers,increasing alkalinity.3.1.2 The pH difference figure(delta pH)is the differencebetween the pH of a solution and its ten-fold dilution.4.Significance and Use4.1 This test method is designed to measure the pH of adistilled water extract of leather.This is considered to be ameasure of the acidity or alkalinity of the leather.Excessiveacidity or alkalinity may have a deleterious effect on the agingcharacteristics of leather.4.2 This test method is suitable for development,control,and service evaluation of leather.5.Interferences5.1 If the leather contains an excessive amount of fats orgreases or has been treated with a material to obtain waterrepellency,the wettability and consequently the extractabilitymay be affected.5.2 If the specimen is difficult or impossible to wet,it maybe treated by any of the following procedures:5.2.1 A vacuum may be used to effect wetting.5.2.2 Mix with the required amount of water for 1 min in adisintegrator.25.2.3 Extract the weighed specimen with a fat solvent in aSoxhlet apparatus for 5 h.Allow the specimen to air until allsolvent has evaporated;then proceed as outlined in Section 10.6.Apparatus6.1 Electronic pH Meter,with a suitable electrode.Themeter shall have an accuracy of at least 0.01 pH unit,andreproducibility of 0.05 pH unit.6.2 Analytical Balance,sensitive to 0.01 g or greater.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,1This test method is under the jurisdiction of ASTM Committee D31 on Leatherand is the direct responsibility of Subcommittee D31.06 on ChemicalAnalysis.Thistest method was developed in cooperation with the American Leather ChemistsAssn.(Standard Method B20 1969).Current edition approved Sept.1,2018.Published September 2018.Originallyapproved in 1969.Last previous edition approved in 2013 as D2810 13.DOI:10.1520/D2810-18.2A Waring Blender has been found satisfactory.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 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.Distilled water shall have a pH value of not lessthan 5.5 nor more than 7.0 and shall give a residue of not morethan 0.5 mg,when 100 mL is evaporated and dried in aplatinum dish.7.3 Commercially Standardized pH Solutions:47.3.1 Alkaline Phosphate Buffer Solution(0.01 M trisodiumphosphate,pH=11.72 at 25 C)Dissolve 1.42 g of anhy-drous disodium hydrogen phosphate(Na2HPO4)in 100 mL ofa 0.1 N carbonate-free solution of sodium hydroxide(NaOH