ASTM_D_7704_-_12.pdf

Designation:D770412Standard Test Method forTotal Aldehydes in Styrene Monomer by PotentiometricTitration1This standard is issued under the fixed designation D7704;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 wet chemical determinationof aldehydes in styrene monomer.Aldehydes are calculatedand reported as benzaldehyde.The range of concentration forthis test method is 0.001 mass%to 0.030 mass%.1.2 In determining conformance of the test results using thismethod to applicable specifications,results shall be rounded offin accordance with the rounding-off method of Practice E29.1.3 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:2D1193 Specification for Reagent WaterD3437 Practice for Sampling and Handling Liquid CyclicProductsD6809 Guide for Quality Control and Quality AssuranceProcedures for Aromatic Hydrocarbons and Related Ma-terialsE29 Practice for Using Significant Digits in Test Data toDetermine Conformance with Specifications2.2 Other Documents:OSHA Regulations,29 CFR paragraphs 1910.1000 and1910.120033.Summary of Test Method3.1 An alcoholic solution of hydroxylamine hydrochlorideis added to a specimen of styrene monomer.Active aldehydespresent react in accordance with Eq 1:RCHO1NH2OHHClRCHNOH1H2O1HCl(1)The amount of hydrochloric acid released,which is equiva-lent to the aldehyde present in the sample,is titrated withstandard alcoholic potassium hydroxide solution.4.Significance and Use4.1 This test method is suitable for determining the quantityof aldehydes,both for quality control and quality assurance ofthe product.5.Interferences5.1 Ketones,if present,interfere by partially reacting withthe reagent.5.2 Methanol used in this procedure may partially react withaldehydes to form(hemi)acetals.6.Apparatus6.1 Titration Vessel,150 mL.6.2 Combined pH Glass Electrode,dedicated for non-aqueous liquids.6.3 Stirring Bar,30 mm.6.4 Titration Stand with stirrer.6.5 Pipets,25 mL.6.6 Volumetric Flasks,100 mL.1This test method is under the jurisdiction of ASTM Committee D16 onAromatic Hydrocarbons and Related Chemicals and is the direct responsibility ofSubcommittee D16.07 on Styrene,Ethylbenzene and C9 and C10 AromaticHydrocarbons.Current edition approved March 1,2012.Published March 2012.Originallyapproved in 2011.Last previous edition approved in 2011 as D7704-11.DOI:10.1520/D770412.2For 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 Standardization Documents Order Desk,DODSSP,Bldg.4,SectionD,700RobbinsAve.,Philadelphia,PA19111-5098,http:/dodssp.daps.dla.mil.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 6.7 Burets,5 mL.(Microburets are preferred.)6.8 Exchange Unit,5 mL.6.9 Thermometers,capable of differentiating 1C at ambi-ent.7.Reagents and Materials7.1 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.4Other 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.7.2 Purity of WaterUnless otherwise indicated,referencesto water shall be understood to mean reagent water as definedby Type III of Specification D1193.7.3 Hydroxylamine Hydrochloride SolutionDissolve 20 gof hydroxylamine hydrochloride(NH2OHHCl)in 1 L ofmethanol.Take a portion of this volume(for example,50 mL)and neutralize(to the first equivalency point)with potassiumhydroxide(KOH)in methanol(7.4).Record the amount ofKOH required and the reading(in mV)of the electrode whenneutralized.For accuracy,repeat this procedure with a secondportion and average the amount of KOH required.Addneutralizing solution(KOH in methanol)to the remaining 900mL of hydroxylamine solution based on the average amountthat was calculated.Check neutrality regularly(for example,once a week)by either checking the reading of the electrode orby titration.7.4 Methanol,free of acids.If necessary,neutralize withpotassium hydroxide(KOH)soluti