1、Designation:D745712Standard Test Method forDetermining Chloride in Aromatic Hydrocarbons andRelated Chemicals by Microcoulometry1This standard is issued under the fixed designation D7457;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revisio
2、n,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 measurement of chloride inaromatic hydrocarbons,their derivatives,and related che
3、micalsas defined by the method.Aromatics typically do not have anysource of chlorides other than organic.The presence of metallicor inorganic chlorides is theoretically possible but not likelyand this method does not purport to address recovery of thosecompounds.1.2 This test method is applicable to
4、 samples with chlorideconcentrations from 0.24 to 5.0 mg/kg.The test method limitof detection(LOD)is 0.07 mg/kg.1.3 This test method is preferred over Test Method D5194for products,such as styrene,that are polymerized by thesodium biphenyl reagent.1.4 In determining the conformance of the test resul
5、ts usingthis method to applicable specifications,results shall berounded off in accordance with the rounding-off method ofPractice E29.1.5 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.6 This standard does not purport to addr
6、ess 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 9.2.Referenced Doc
7、uments2.1 ASTM Standards:2D1193 Specification for Reagent WaterD1555M Test Method for Calculation of Volume and Weightof Industrial Aromatic Hydrocarbons and CyclohexaneMetricD3437 Practice for Sampling and Handling Liquid CyclicProductsD3505 Test Method for Density or Relative Density of PureLiquid
8、 ChemicalsD4052 Test Method for Density,Relative Density,and APIGravity of Liquids by Digital Density MeterD5194 Test Method for Trace Chloride in Liquid AromaticHydrocarbonsD6809 Guide for Quality Control and Quality AssuranceProcedures for Aromatic Hydrocarbons and Related Ma-terialsE29 Practice f
9、or Using Significant Digits in Test Data toDetermine Conformance with SpecificationsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method2.2 Other Document:OSHA Regulations,29 CFRparagraphs 1910.1000 and1910.120033.Terminology3.1 Definitions of Terms Specif
10、ic to This Standard:1This test method is under the jurisdiction of ASTM Committee D16 onAromatic Hydrocarbons and Related Chemicals and is the direct responsibility ofSubcommittee D16.04 on Instrumental Analysis.Current edition approved Jan.1,2012.Published February 2012.Originallyapproved in 2011.L
11、ast previous edition approved in 2011 as D7457-111.DOI:10.1520/D745712.2For 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 web
12、site.3Available from U.S.Government Printing Office Superintendent of Documents,732 N.Capitol St.,NW,Mail Stop:SDE,Washington,DC 20401,http:/www.access.gpo.gov.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 3.1.1 calibration factor/recov
13、ery factor,nan indication ofthe efficiency of the measurement computed by dividing themeasured value of a standard by its theoretical value.3.1.2 dehydrating tube or drying vessel,na chambercontaining concentrated sulfuric acid that scrubs the combus-tion effluent gases to remove water vapor prior t
14、o entering thetitration cell.3.1.3 endpoint routine/test titration,nprocesses whichallow the coulometer to set the endpoint and gain values to beused for sample analysis.3.1.4 oxidative pyrolysis,na process in which a sample isevaporated in an inert gas atmosphere and combusted after-wards completel
15、y in an oxygen-rich atmosphere at high tem-perature to break down the components of the sample intoelemental oxides.3.1.5 reference electrode,nused in conjunction with sen-sor electrode to measure the potential of the titration cell.3.1.6 sensor electrode,ndetects changes in silver ionconcentration.
16、3.1.7 titration cell,nvessel that contains the sensor-reference electrode pair and generator electrode pair along withthe cell electrolyte.3.1.8 titration parameters,nvarious instrumental condi-tions that can be changed for different types of analysis andanalyzers.3.1.9 working electrode pair(generator electrode),nanelectrode pair consisting of an anode and a cathode.4.Summary of Test Method4.1 An aliquot of sample is introduced into a combustiontube maintained at 900 to 1100C having a flowing s
