1、Designation: D1492 13Standard Test Method forBromine Index of Aromatic Hydrocarbons by CoulometricTitration1This standard is issued under the fixed designation D1492; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last
2、 revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () 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 isusuall
3、y applied to materials having bromine indexes below500.NOTE 1Other test methods for determining bromine-reactive materialare Test Methods D1159, D1491, D2710, and D5776.1.2 This test method has been found applicable to aromatichydrocarbons containing no more than trace amounts of olefinsand that are
4、 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 “to the
5、 nearest unit” in the last right-hand digitused in expressing the specification limit, in accordance withthe rounding-off method of Practice E29.1.4 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.5 This standard does not purp
6、ort 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 a specifichazard statement see Section 8.
7、2. Referenced Documents2.1 ASTM Standards:2D891 Test Methods for Specific Gravity,Apparent, of LiquidIndustrial ChemicalsD1159 Test Method for Bromine Numbers of PetroleumDistillates and Commercial Aliphatic Olefins by Electro-metric TitrationD1193 Specification for Reagent WaterD1491 Test Method fo
8、r Test for Bromine Index of AromaticHydrocarbons by Potentiometric Titration (Withdrawn1985)3D2710 Test Method for Bromine Index of Petroleum Hydro-carbons by Electrometric TitrationD3437 Practice for Sampling and Handling Liquid CyclicProductsD3505 Test Method for Density or Relative Density of Pur
9、eLiquid ChemicalsD4052 Test Method for Density, Relative Density, and APIGravity of Liquids by Digital Density MeterD5776 Test Method for Bromine Index of Aromatic Hydro-carbons by Electrometric TitrationD6809 Guide for Quality Control and Quality AssuranceProcedures for Aromatic Hydrocarbons and Re
10、lated Ma-terialsE29 Practice for Using Significant Digits in Test Data toDetermine Conformance with Specifications2.2 Other Document:OSHA Regulations, 29 CFR paragraphs 1910.1000 and1910.120043. Terminology3.1 Definitions:3.1.1 bromine index (B), nthe number of milligrams (mg)of bromine consumed by
11、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 withelectrolytically generated bromine at room temperature. Theend point is determined by a dead-stop method. The time oftitration is proportional to the bromine added to
12、the specimen.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 July 15, 2013. Published September 2013. Originallyapproved in 1957. L
13、ast previous edition approved in 2008 as D1492 081. DOI:10.1520/D1492-13.2For 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 A
14、STM website.3The last approved version of this historical standard is referenced onwww.astm.org.4Available 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.*A Summary of Changes section appears at
15、the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States15. Significance and Use5.1 This test method is useful for setting specification, foruse as an internal quality control tool, and for use in develop-ment or resear
16、ch 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.6. Apparatus6.1 Amperometric-Coulometric Apparatus, automatic, suit-able for bromine index titrations w
17、ith 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 shall beused in all tests. Unless otherwise indicated, it is in
18、tended 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 reagent is ofsufficiently high purity to permit its use wi
19、thout 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 D1193.7.3 Electrolyte:7.3.1 Preparation Cell ElectrolyteTo make 1 L, mix 600mL of glacial acetic acid, 26
20、0 mL of absolute methanol, and140 mL of KBr solution (119g/L).7.4 Potassium Bromide Solution (119 g/L)Dissolve 119 gof potassium bromide (KBr) in water and dilute to 1 L.5Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the tes
21、ting 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.FIG. 1 Automatic Amperometric-Coulometric Titr
22、ator CircuitD1492 1328. Hazards8.1 Consult current OSHA regulations, suppliers MaterialSafety Data Sheets, and local regulations for all materials usedin this test method.9. Sampling9.1 Sample the material in accordance with Practice D3437.10. Procedure10.1 Place 125 mL of electrolyte in a clean, dr
23、y titrationcell, insert the electrodes, and begin stirring. Verify the volumeof 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
24、the specimen and immediatelybefore each determination, bring the coulometer to equilib-rium.10.3 Draw into the syringe the amount of sample prescribedin Table 1 corresponding to the estimated bromine index. Wipethe needle with a clean cloth, attach a rubber cap seal to theneedle, and weigh on the an
25、alytical 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 is known(Test Methods D891, D3505,orD4052 can be used), the specimen can b
26、eadded by means of a pipet or microburet and the weight calculated.10.4 Begin titration of the specimen. As the titrationproceeds, keep the generation current at the selected value. Thegeneration of bromine will continue as long as it is consumedby the sample. At the end point an incremental increas
27、e 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 and the titration may be consideredcomplete. Otherwise, it may be necessary to c
28、ontinue 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/100 g),asfollows:B 5T 3 I 379.9965W(1)where:T = titration time, sI = generation
29、 current, mAW = weight of specimen, g79.9 = MW bromine (grams/mole), and965 = Faradays constant (96 500 coulomb/mole)/10012. Report12.1 Report the following information:12.1.1 Report bromine index to the nearest unit.13. Precision and Bias13.1 PrecisionA ruggedness study was performed byanalyzing th
30、ree samples 20 times and one sample five timeseach over the shortest practical time. The calculated repeat-ability is shown in Table 2.13.2 RepeatabilitySee Table 2.13.3 ReproducibilityTo be determined.14. Quality Guidelines14.1 Refer to Guide D6809 for suggested QA/QC activitiesthat can be used as
31、a part of this test method. It is recom-mended that the operator of this test method select and performrelevant QA/QC activities like the ones in Guide D6809 to helpensure the quality of data generated by this test method.15. Keywords15.1 aromatic hydrocarbons; bromine index; bromine-reactive; coulo
32、metric titration; titrationTABLE 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 5.0TABLE 2 RepeatabilityASample Name Replicates (n)Conc. mg-Br/100 gr997.5 mg-Br/100g Std 20 1012 39.1Toluene-Pit E
33、PX 20 31.2 2.9Xylene-Plant Feed 20 10.7 2.3Reformate-Feed 5 670 53.9ARepeatability = SD * 2.8.D1492 133SUMMARY OF CHANGESCommittee D16 has identified the location of selected changes to this standard since the last issue(D1492-081) that may impact the use of this standard. (Approved July 15, 2013.)(
34、1) Deleted Section 1.5.(2) Deleted Section 7.3.(3) Changed Section 7.3.2 to Section 7.3.1.(4) Deleted Section 13.1 through 13.1.3.(5) Changed Section 13.2.1 to Section 13.1.(6) Changed Section 13.2.2 to Section 13.2.(7) Changed Section 13.2.3 to Section 13.3.ASTM International takes no position resp
35、ecting 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 responsibility.This s
36、tandard 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 Interna
37、tional 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 shown bel
38、ow.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). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).D1492 134
