ASTM_D_2810_-_13.pdf

Designation:D281013Standard 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 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.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: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.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 pH Meter,either battery or line-operated with a suitableelectrode.The meter shall have a resolution of 0.1/0.01 pHunit,and shall have a relative accuracy of 60.1/0.01 pH unit.6.2 Analytical Balance,sensitive to 0.01 g.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.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.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 May 1,2013.Published May 2013.Originallyapproved in 1969.Last previous edition approved in 2007 as D2810 07.DOI:10.1520/D2810-13.2A Waring Blender has been found satisfactory.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.Pharmacopeial Convention,Inc.(USPC),Rockville,MD.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 7.3 Standard pH Solutions:47.3.1 Alkaline Phosphate Buffer Solution(0.01 M trisodiumphosphate,pH=11.72 at 25C)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)and dilute to 1 L with water.7.3.2 Borax Buffer Solution(0.01 M,pH=9.18 at 25C)Dissolve 3.81 g of sodium tetraborate decahydrate(Na2B4O710 H2O)in water and dilute to 1 L.7.3.3 Hydrochloric Acid(pH=1.10 at 25C)Add 2 g ofconcentrated hydrochloric acid(HCl,sp gr 1.19)to 450 g ofwater.Standardize and dilute to 0.1 N.7.3.4 Phosphate Buffer Solution(0.025 M with respect toeach phosphate,salt pH=6.86 at 25C)Dis