1、Designation: D 1492 07Standard Test Method forBromine Index of Aromatic Hydrocarbons by CoulometricTitration1This standard is issued under the fixed designation D 1492; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of la
2、st 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. Scope*1.1 This test method covers the determination of the amountof bromine-reactive material in aromatic hydrocarbons. It isusu
3、ally applied to materials having bromine indexes below500.NOTE 1Other test methods for determining bromine-reactive materialare Test Methods D 1159, D 1491, D 2710, and D 5776.1.2 This test method has been found applicable to aromatichydrocarbons containing no more than trace amounts of olefinsand t
4、hat are substantially free from material lighter thanisobutane and have a distillation end point under 288C.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
5、“to the nearest unit” in the last right-hand digitused in expressing the specification limit, in accordance withthe rounding-off method of Practice E29.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of thi
6、s standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. For a specifichazard statement see Section 8.2. Referenced Documents2.1 ASTM Standards:2D 891 Test Methods for Specific Gravity, Apparent, ofLiquid Industrial Che
7、micalsD 1159 Test Method for Bromine Numbers of PetroleumDistillates and Commercial Aliphatic Olefins by Electro-metric TitrationD 1193 Specification for Reagent WaterD 1491 Test Method for Bromine Index of Aromatic Hy-drocarbons by Potentiometric Titration3D 2710 Test Method for Bromine Index of Pe
8、troleum Hy-drocarbons by Electrometric TitrationD 3437 Practice for Sampling and Handling Liquid CyclicProductsD 3505 Test Method for Density or Relative Density ofPure Liquid ChemicalsD 4052 Test Method for Density and Relative Density ofLiquids by Digital Density MeterD 5776 Test Method for Bromin
9、e Index of Aromatic Hy-drocarbons by Electrometric TitrationD 6809 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 Document:OSHA Regul
10、ations, 29 CFR, paragraphs 1910.1000 and1910.120043. Terminology3.1 Definition:3.1.1 bromine index (B), nthe number of milligrams (mg)of bromine consumed by 100 g of sample under givenconditions (mg-Br/100 g).4. Summary of Test Method4.1 The specimen is added to a solvent and titrated withelectrolyt
11、ically generated bromine at room temperature. Theend point is determined by a dead-stop method. The time oftitration is proportional to the bromine added to the specimen.5. Significance and Use5.1 This test method is useful for setting specification, foruse as an internal quality control tool, and f
12、or use in develop-ment or research work on industrial aromatic hydrocarbons andrelated materials. This test method gives a broad indication ofolefinic content. It will not differentiate between the types ofaliphatic unsaturation.1This test method is under the jurisdiction of ASTM Committee D16 onAro
13、matic Hydrocarbons and Related Chemicals and is the direct responsibility ofSubcommittee D16.04 on Instrumental Analysis.Current edition approved Feb. 1, 2007. Published March 2007. Originallyapproved in 1957. Last previous edition approved in 2002 as D 1492 02.2For referenced ASTM standards, visit
14、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.3Withdrawn.4Available from U.S. Government Printing Office Superintendent of Documents,732 N. Capit
15、ol St., NW, Mail Stop: SDE, Washington, DC 20401, http:/www.access.gpo.gov.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.6. Apparatus6.1 Amperometric-Coulometric App
16、aratus, automatic, suit-able for bromine index titrations with variable generatorcurrent and timer. A typical circuit diagram of suitable equip-ment is shown in Fig. 1.6.2 Syringe, 2 mL with needle and rubber cap seal.6.3 Stirrer, magnetic.7. Reagents7.1 Purity of ReagentReagent grade chemicals shal
17、l 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.5Other grades may beused, provided it is first ascertained that the
18、 reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the determination.7.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean reagent water conformingto Type IV of Specification D 1193.7.3 ElectrolyteTo make 1 L, mix 600 mL
19、of glacial aceticacid, 260 mL of absolute methanol, and 140 mL of KBrsolution (119 g/L). Dissolve2gofMercury II acetate in thismixture.7.4 Potassium Bromide Solution (119 g/L)Dissolve 119 gof potassium bromide (KBr) in water and dilute to 1 L.8. Hazards8.1 Consult current OSHA regulations, suppliers
20、 MaterialSafety Data Sheets, and local regulations for all materials usedin this test method.9. Sampling9.1 Sample the material in accordance with PracticeD 3437.10. Procedure10.1 Place 125 mL of electrolyte in a clean, dry titrationcell, insert the electrodes, and begin stirring. Verify the volumeo
21、f electrolyte is sufficient to ensure the electrodes are com-pletely submerged and if necessary, increase the volume ofelectrolyte required. Apply the generation current in accor-dance with Table 1.10.2 Before introducing the specimen and immediatelybefore each determination, bring the coulometer to
22、 equilib-rium.5Reagent 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 S
23、tates Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.FIG. 1 Automatic Amperometric-Coulometric Titrator CircuitD149207210.3 Draw into the syringe the amount of sample prescribedin Table 1 corresponding to the estimated bromine index. Wipethe needle with
24、a clean cloth, attach a rubber cap seal to theneedle, and weigh on the analytical balance. Remove the seal,add the specimen to the electrolyte, and set the timer to zero.Replace the seal, reweigh the syringe, and calculate thespecimen weight.NOTE 2If the density or specific gravity of the specimen i
25、s known(Test Methods D 891, D 3505,orD 4052 can be used), the specimen canbe added by means of a pipet or microburet and the weight calculated.10.4 Begin titration of the specimen. As the titration pro-ceeds, keep the generation current at the selected value. Thegeneration of bromine will continue a
26、s long as it is consumedby the sample. At the end point an incremental increase inbromine concentration causes the titration and timer to stopautomatically. Forty seconds after the titration has shut off,continue the titration. If the titration cuts off, immediately, theend point has been reached an
27、d the titration may be consideredcomplete. Otherwise, it may be necessary to continue thetitration in steps, waiting about 40 s between steps, until thetitration time increment is4sorless. Note the total titrationtime and generation current.11. Calculation11.1 Calculate the bromine index, B (mg-Br/1
28、00 g),asfollows:B 5T 3 I 3 79.9965W(1)where:T = titration time, sI = generation current, mAW = weight of specimen, g79.9 = MW bromine (grams/mole)965 = Faradays constant (96 500 coulomb/mole)/10012. Report12.1 Report the following information:12.1.1 Report bromine index to the nearest unit.13. Preci
29、sion and Bias13.1 Precision data were generated using titrators fromCentral Scientific Co. The precision obtained using titratorsfrom other suppliers has not been determined.13.2 PrecisionThe following data should be used forjudging the acceptability of results (95 % probability) forbromine indexes
30、from 0 to 50:13.2.1 Intermediate Precision (formerly calledRepeatability)The standard deviation is 0.39. Duplicateresults by the same operator should be considered suspect ifresults differ by more than 1.15.NOTE 3Number of data used, 91; number of degrees of freedom, 61;number of cooperating laborat
31、ories, 4.13.2.2 ReproducibilityThe standard deviation is 1.43. Theresults submitted by two laboratories should be consideredsuspect if they differ by more than 4.1.NOTE 4Number of data used, 41; number of degrees of freedom, 30;number of cooperating laboratories, 4.13.3 BiasThe procedure in this tes
32、t method has no biasbecause the value of bromine index can be defined only interms of a test method.14. Quality Guidelines14.1 Refer to Guide D 6809 for suggested QA/QC activitiesthat can be used as a part of this test method. It is recom-mended that the operator of this test method select and perfo
33、rmrelevant QA/QC activities like the ones in Guide D 6809 tohelp ensure the quality of data generated by this test method.15. Keywords15.1 aromatic hydrocarbons; bromine index; bromine-reactive; coulometric titration; titrationSUMMARY OF CHANGESSubcommittee D16.07 has identified the location of sele
34、cted changes to this standard since the last issue(D 6809 - 02) that may impact the use of this standard. (Approved February 1, 2007.)(1) Updated 2.1 to add reference to Guide D 6809.(2) Updated footnotes for 2.1 and 2.2 as specified in D16Editorial Guidelines for Preparation and Revision of Standar
35、ds.(3) Modified 3.1.1 to further clarify the definition of bromineindex (B) by adding the weight and concentration units mgand mg-br/100 g.(4) Modified 11.1 by adding the units mg-Br/100 g and theunit definition of constants used in the calculation of bromineindex.(5) Added Section 14 on QA/QC refer
36、encing Guide D 6809specified in D16 Editorial Guidelines for Preparation andRevision of Standards.TABLE 1 Specimen Size and Generation CurrentEstimatedBromine IndexSpecimen Weight,gGenerationCurrent, mA0 to 20 1.000 1.020 to 200 0.600 5.0200 to 2000 0.060 5.0D1492073ASTM International takes no posit
37、ion respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibilit
38、y.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM
39、 International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address s
40、hown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).D1492074
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