ASTM_D_2930_-_03.pdf

Designation:D 2930 03Standard Test Method forMaleic Acid in Maleic Anhydride by Potentiometric Titration1This standard is issued under the fixed designation D 2930;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(e)indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers the determination of free maleicacid in refined maleic anhydride by potentiometric titration.1.2 This test method is applicable for all concentrations ofmaleic acid;however,it is primarily used for concentrationsbelow 0.5%.1.3 The following applies to all specified limits in thisstandard:For purposes of determining conformance with thisstandard,an observed value or a calculated value shall berounded off“to the nearest unit”in the last right-hand digitused in expressing the specification limit,in accordance withthe rounding-off method of Practice E 29.1.4 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.For specific hazardstatements,see Section 7.2.Referenced Documents2.1 ASTM Standards:D 1193 Specification for Reagent Water2D 3438 Practice for Sampling and Handling Naphthalene,Maleic Anhydride,and Phthalic Anhydride3E 29 Practice for Using Significant Digits in Test Data toDetermine Conformance with Specifications42.2Other Documents:OSHA Regulations,29 CFR,paragraphs 1910.1000 and1910.1200.53.Summary of Test Method3.1 This test method is based on a direct titration of maleicacid using a tertiary amine as the base.The titration is carriedout in an anhydrous solvent system and followed potentio-metrically by means of a pH meter.Tertiary amines do not reactwith anhydrides.Only one carboxylic acid group is titrated.4.Significance and Use4.1 The maleic acid content is usually an indication ofexposure to moisture in air.Maleic anhydride reacts withmoisture to form maleic acid.5.Apparatus5.1 Titrimeter or pH meter,equipped with glass and calomelelectrodes.The pair of electrodes shall be mounted to extendwell below the liquid level.5.2 Microburet,5 or 10-mL size,graduated 20 divisions/mL.5.3 Stirrer,mechanical,that will furnish a rapid stirringaction,but not such vigorous stirring that air bubbles will bedrawn to the electrodes of the titrimeter or pH meter.5.4 Beaker,250-mL,tall-form.5.5 Automatic Titrator can be used in place of the aboveapparatus.6.Reagents6.1 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.6Other 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.6.2 Purity of WaterUnless otherwise indicated,referencesto water shall be understood to mean reagent water conformingto Type IV of Specification D 1193.1This test method is under the jurisdiction of ASTM Committee D16 onAromatic Hydrocarbons and Related Chemicals and is the direct responsibility ofSubcommittee D16.02 on Oxygenated Aromatics.Current edition approved Jan.10,2003.Published March 2003.Originallyapproved in 1970.Last previous edition approved in 1994 as D 2930 94.2Annual Book of ASTM Standards,Vol 11.01.3Annual Book of ASTM Standards,Vol 06.04.4Annual Book of ASTM Standards,Vol 14.02.5Available from U.S.Government Printing Office Superintendent of Documents,732 N.Capitol St.,NW,Mail Stop:SDE,Washington,DC 20401.6Reagent 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.1Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959,United States.6.3 Acetone,dried over Linde Type 5A molecular sieves.76.4 N-ethylpiperidine8(0.05 N in acetone)Dissolve 5.65 gof N-ethylpiperidine in acetone and dilute to 1 L.Prepare freshdaily.6.5 Maleic Acid9Titrate with aqueous NaOH solution(0.5N)to a phenolphthalein end point to obtain assay.7.Hazards7.1 Consult current OSHA regulations,suppliers MaterialSafety Data Sheets,and local regulations for all materials usedin this test method.7.2 In addition to other precautions,handling of maleicanhydride shall be done with care.Although it is a solid atambient temperatures,its vapor pressure is high enough tocause objectionable fumes.