ASTM_D_6657_-_14ae1.pdf

Designation:D665714a1Standard Test Method forpH of Wet Blue1This standard is issued under the fixed designation D6657;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.1NOTEParagraph 9.1.3 was added editorially in November 2014.1.Scope1.1 This test method covers the determination of the pH ofall types of wet blue and wet white.1.2 For pH of wet white,the procedure is identical,substi-tute wet white for wet blue in the standard method.1.3 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.4 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:2D6659 Practice for Sampling and Preparation of Wet Bluefor Physical and Chemical TestsE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3.Terminology3.1 Definitions of Term 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 24 C.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 wet blue.This is considered to be ameasure of the acidity or alkalinity of the wet blue.Excessiveacidity or alkalinity may have a deleterious effect on the agingcharacteristics of wet blue and the leather made from it.4.2 This test method is suitable for development,control,and service evaluation of wet blue.5.Apparatus5.1 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.5.2 Analytical Balance,sensitive to 0.01 g or greater.6.Reagents6.1 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.6.2 Commercially Standardized pH Solutions3:6.2.1 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)and dilute to 1 L with water.6.2.2 Borax Buffer Solution(0.01 M,pH=9.18 at 25C)Dissolve 3.81 g of sodium tetraborate decahydrate(Na2B4O7 10H2O)in water and dilute to 1 L.6.2.3 Hydrochloric Acid(pH=1.10 at 25 C)Add 2 g ofconcentrated hydrochloric acid(HCl,sp gr 1.19)to 450 g ofwater.Standardize and dilute to 0.1 N.6.2.4 Phosphate Buffer Solution(0.025 M with respect toeach phosphate,salt pH=6.86 at 2.5 C)Dissolve 3.40 g ofmonobasic potassium phosphate(KH2PO4)and 3.55 g ofanhydrous dibasic sodium phosphate(Na2HPO4)in water anddilute to 1 L.1This test method is under the jurisdiction of ASTM Committee D31 on Leatherand is the direct responsibility of Subcommittee D31.02 on Wet Blue.Current edition approved May 1,2014.Published June 2014.Originallyapproved in 2001.Last previous edition approved in 2014 as D6657-14.DOI:10.1520/D6657-14AE01.2For 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.3Commercial buffer salts and solutions prepared in accordance with NationalBureau of Standards recommendations are sold by reputable laboratory supplyhouses and may be used.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 6.2.5 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.7.Test Specimen7.1 The specimen shall consist of a composite sampleprepared according to Practice D6659.7.1.1 Practice D6659Sample Preparation Method A(asreceived in wet state,diced):use 10 6 1 g.7.1.2 Practice D6659Sample Preparation Method B(oven or air dried,ground):use 2-5 g.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.Washelectrodes by immersing in three changes of water and estab-lish a fresh liquid junction after blotting electrodes if usingsleeve type e