ASTM_D_4589_-_96.pdf

Designation:D 4589 96Standard Test Method forNitrobenzene in Aniline1This standard is issued under the fixed designation D 4589;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 a polarographic procedure forthe determination of nitrobenzene in aniline.1.2 This test method has been found applicable to thedetermination of nitrobenzene in aniline containing concentra-tions of not more than 25 mg/kg nitrobenzene.1.3 The following applies to all specified limits in this testmethod:for purposes of determining conformance with thistest method,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 10 and Note 3.2.Referenced Documents2.1 ASTM Standards:D 1193 Specification for Reagent Water2D 1549 Test Method for Zinc in Lubricating Oils andAdditives(Polarographic Method)3D 3436 Practice for Sampling and Handling Aniline4D 4790 Terminology of Aromatic Hydrocarbons and Re-lated Chemicals4E 29 Practice for Using Significant Digits in Test Data toDetermine Conformance with Specifications5E 50 Practices for Apparatus,Reagents,and Safety Precau-tions for Chemical Analysis of Metals62.2Other Document:OSHA Regulations,29 CFR,paragraphs 1910.1000 and1910.120073.Terminology3.1 See Terminology D 4790 for definition of terms used inthis test method.4.Summary of Test Method4.1 Polarography is an electrochemical method of analysis.A quantitative evaluation of an electro-reducible material suchas nitrobenzene can be determined by measuring the charac-teristic current flow,as a function of an increasingly appliedvoltage,resulting from the solution undergoing electrolysis.4.2 The current flowing through the specimen during theanalysis is in the microampere range so several polarogramscan be obtained on the same specimen solution withoutsignificant differences.4.3 The nitrobenzene content is determined by mixing fourvolumes of aniline with one volume of concentrated hydro-chloric acid.The diffusion current of nitrobenzene is thenmeasured by polarographic technique.A standard calibrationgraph is developed with various concentrations of nitrobenzenein aniline versus their diffusion currents.A reading of thediffusion current level of the test specimen from the calibrationgraph determines its nitrobenzene content.5.Significance and Use5.1 This test method gives a quantitative means of detectionof nitrobenzene in industrial grade aniline both for qualitycontrol and quality assurance of the product.6.Interferences6.1 Since the diffusion coefficient for solutions of organicmolecules can possibly increase up to 2%per degree rise intemperature,the polarographic cell temperature should berelatively the same when comparing specimen analyses withstandard calibration analyses.6.2 The sensitivity of an analysis is affected by the dimen-sions of the dropping mercury electrode(DME)capillary andalso by the height of the mercury column above the electrode.It is advisable to use the same DME capillary with a constanthead of mercury that will yield a uniform dropping rate duringa series of analyses.Recalibrate when the DME is changed.6.3 Sudden or severe vibrations of the DME system cancause interferences in the resulting polarogram.6.4 Residual dissolved oxygen in the specimen solution willinterfere with the analysis.This test method includes a nitrogenpurge to remove dissolved oxygen.1This test method is under the jurisdiction of ASTM Committee D-16 onAromatic Hydrocarbons and Related Chemicals and is the direct responsibility ofSubcommittee D16.0D on Organic Nitrogen Compounds.Current edition approved Dec.10,1996.Published February 1997.Originallypublished as part of D 3264 73 T.Last previous edition D 3264 91.2Annual Book of ASTM Standards,Vol 11.01.3Discontinued 1984:see 1984 Annual Book of ASTM Standards,Part 23.4Annual Book of ASTM Standards,Vol 06.04.5Annual Book of ASTM Standards,Vol 14.02.6Annual Book of ASTM Standards,Vol 03.05.7Available from Superintendent of Documents,U.S.Government PrintingOffice,Washington,DC 20402.1AMERICAN SOCIETY FOR TESTING AND MATERIALS100 Barr Harbor Dr.,West Conshohocken,PA 19428Reprinted from the Annual Book of ASTM Standards.Copyright ASTM7.Apparatus7.1 Recording PolarographHowever,a nonrecording po-larograph may be adapted for this test method.7.2 Electrodes:7.2.1 Dr