ASTM_D_7637_-_10_2015.pdf

Designation:D763710(Reapproved 2015)Standard Test Method forDetermination of Glycerin Assay by Titration(Sodium MetaPeriodate)1This standard is issued under the fixed designation D7637;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 provides the quantitative determinationof glycerin by the titrimetric method.It is applicable to allglycerin or glycerin/water mixtures 75%.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 may involve hazardous materials,opera-tions and equipment.This standard does not purport to addressall of the safety problems associated with its use.It is theresponsibility of whoever uses this standard to consult theestablished and appropriate safety and health practices anddetermine the applicability of regulatory limitations prior touse.Specific precautions are listed in Section 8.2.Referenced Documents2.1 ASTM Standards:2D1193 Specification for Reagent WaterD4725 Terminology for Engine Coolants and Related FluidsE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method2.2 Other Standards:The United States Pharmacopoeia 31 Glycerin Monograph Assay Method3AOCS Official Method EA 6-94(Replaces AOCS EA 6-51),Determination of Crude Glycerin,Titrimetric Method4BS 5711:Part 3,1979 Sampling and Test for Glycerol-Determination of Glycerol Content53.Terminology3.1 Definitions:3.1.1 glycerinpropane-1,2,3-triol,C3H5(OH)3(alsoknownasglycerine),1,2,3-propanetriol,1,2,3-trihydroxypropane,glyceritol,glycyl alcohol,glycerol.CAS#56-81-5.3.1.2 SMPSodium Meta Periodate.3.1.3 Forotherdefinitionsoftermsusedinthisspecification,refer to Terminology D4725.4.Significance and Use4.1 This test method is based on the cold oxidation of theglycerol by sodium metaperiodate in a strong acidic medium.Formaldehyde and formic acid are produced in this reactionand the latter is used to measure the glycerol content bytitration with standard sodium hydroxide solution,to a pH 8.16 0.1.The glycerol content is expressed as a percentage(m/m).CH2OH2 CHOH2 CH2OH12 NaIO4(1)HCOOH12 HCHO12 NaIO31H2O4.2 InterferencesThe glycerin sample should be free oforganic compounds with more than two hydroxyl groups onadjacent carbon atoms(for example,sugars,glycols).Thesetypes of compounds may produce formic acid which interfereswith the determination of the glycerol content.5.Apparatus5.1 Burette50 mL“Type A”unit that can deliver 30 dropsper mL and calibrated to meet the NIST standards.NOTE1 It is critical that all glassware be“Type A”and thoroughlycleaned before use as dirty glassware will impact the analysis results.5.2 pH meter,fitted with glass electrode.NOTE2The pH meter should be standardized with a minimum of two1This test method is under the jurisdiction of ASTM Committee D15 on EngineCoolants and Related Fluids and is the direct responsibility of SubcommitteeD15.93 on Research and Long Range Planning.Current edition approved May 1,2015.Published June 2015.Originallyapproved in 2010.Last previous edition approved in 2010 as D763710.DOI:10.1520/D7637-10R15.2For 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.3Available from U.S.Pharmacopeia(USP),12601 Twinbrook Parkway,Rockville,MD 20852-1790,http:/www.usp.org.4Available from American Oil Chemists Society(AOCS),2710 S.Boulder,Urbana,IL 61802-6996,http:/www.aocs.org.5Available from British Standards Institute(BSI),389 Chiswick High Rd.,London W4 4AL,U.K.,http:/.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 buffer solutions at 10.0 and 7.0.(See 7.12.)5.3 Stirrerpreference should be given to a magnetic stir-rer.In this case,check that it does not influence the pH meter.6.Purity of Reagents and Water6.1 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.Other grades may be usedprovided it is first ascertained that the reagent is of sufficientlyhigh purity to permit its use without lessening the accuracy ofthe determination.6.2 Purity of WaterUnless indicated otherwise,referencesto water shall be understood to mean Type II reagent water asdefined in Specification D1193.NOTE3The presence of carbon dioxide can introduce errors;thereforeit is advisable to prepare 500 mLof wate