ASTM_D_4569_-_06_2012.pdf

Designation:D456906(Reapproved 2012)Standard Test Method forRubber Compounding MaterialsDetermination of Acidity inSulfur1This standard is issued under the fixed designation D4569;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 acidmaterial,which disassociates in distilled water,that is presentin sulfur.The acidity is determined by an electrometric orvisual titration.1.2 The values stated in SI units are to be regarded as thestandard.The values given in parentheses are for informationonly.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:2D4483 Practice for Evaluating Precision for Test MethodStandards in the Rubber and Carbon Black ManufacturingIndustries3.Significance and Use3.1 This test method provides a means of determining theacidity of sulfur and may be used for quality control,researchand development,or for any other reason for which such adetermination is required.A low acidity value indicates to theuser that the sulfur used should not adversely affect thevulcanization system.4.Apparatus4.1 pH Meter,equipped with a glass measuring electrodeand calomel reference electrode,operated according to themanufacturers directions for optimum performance.4.2 10 cm3Burette,with 0.05 cm3graduations.4.3 Laboratory Glassware,suitable for carrying out theprocedure as written.5.Reagents5.1 Purity of ReagentsReagent grade chemicals shall beused in all tests.Unless otherwise indicated,it is intended thatall reagents conform to the specifications of the Committee onAnalytical Reagents of the American Chemical Society wheresuch specifications are available.3Other grades may be used,provided it is first ascertained that the reagent is of sufficientlyhigh purity to permit its use without lessening the accuracy ofthe determination.5.2 BromothymolBlueDissolve0.1gof3,3-dibromothymolsulfonphthalein in 100 cm3of 20%methanolor use commercical preparations.5.3 Sodium Hydroxide,0.01 N.6.Procedure6.1 Weigh 10.0 g of sulfur into a 500-cm2beaker,and wetthe sample with 25 cm3of alcohol.6.2 Add 200 cm3of distilled water,and stir the wetted sulfurthoroughly.6.3 Place the pH meter electrode in the solution and titratewith 0.01 N NaOH to a pH of 7.0.Stir the mixture constantlywhile titrating.When nearing the end of the titration,wait untilthe pH reading has reached equilibrium before adding addi-tional NaOH solution to prevent overshooting the end point.6.4 If a pH meter is unavailable,add 10 drops of bromo-thymol blue indicator and titrate as above.6.5 Important:Titrate a blank(no sulfur)using the sameamounts of alcohol and water to a pH 7.0 end point.Subtract1This test method is under the jurisdiction of ASTM Committee D11 on Rubberand is the direct responsibility of Subcommittee D11.11 on Chemical Analysis.Current edition approved May 1,2012.Published June 2012.Originallyapproved in 1986.Last previous edition approved in 2006 as D4569 06.DOI:10.1520/D4569-06R12.2For 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 the amount used for the blank from the amount used to titratea sulfur sample in order to determine the acidity of the sulfursample.7.Calculation7.1 Calculate the percent acidity,A,(as H2SO4)in accor-dance with the following equation:A 5 4.93V 3N/W(1)where:V=volume of NaOH for sample-volume NaOH for blank,cm3,N=normality of NaOH solution,andW=sample mass,g.8.Report8.1 Report the following information:8.1.1 Percent acidity as H2SO4.8.1.2 If the pH of the sulfur solution is greater than 7.0 andno titrant is needed,report the result as basic.9.Precision and Bias49.1 This precision and bias section has been prepared inaccordance with Practice D4483.Refer to Practice D4483 forterminology and other statistical details.9.2 The precision results in this precision and bias sectiongive an estimate of the precision of this