1、Designation: D 1492 08Standard 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 () 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 isusua
3、lly 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 th
4、at 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 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 no
6、t 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 a specifichazard statement see Sect
7、ion 8.2. Referenced Documents2.1 ASTM Standards:2D 891 Test Methods for Specific Gravity, Apparent, ofLiquid Industrial ChemicalsD 1159 Test Method for Bromine Numbers of PetroleumDistillates and Commercial Aliphatic Olefins by Electro-metric TitrationD 1193 Specification for Reagent WaterD 1491 Tes
8、t Method for Bromine Index of Aromatic Hy-drocarbons by Potentiometric Titration3D 2710 Test Method for Bromine Index of Petroleum Hy-drocarbons by Electrometric TitrationD 3437 Practice for Sampling and Handling Liquid CyclicProductsD 3505 Test Method for Density or Relative Density ofPure Liquid C
9、hemicalsD 4052 Test Method for Density and Relative Density ofLiquids by Digital Density MeterD 5776 Test Method for Bromine Index of Aromatic Hy-drocarbons by Electrometric TitrationD 6809 Guide for Quality Control and Quality AssuranceProcedures for Aromatic Hydrocarbons and Related Ma-terialsE29
10、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 Definition:3.1.1 bromine index (B), nthe number of milligrams (mg)of bromine consumed by 100 g of sample under
11、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 the specimen.5. Signif
12、icance 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 research work on industrial aromatic hydrocarbons and1This test method is under the jurisdiction of ASTM Committee D16 onAromatic Hydrocarbons and Relate
13、d Chemicals and is the direct responsibility ofSubcommittee D16.04 on Instrumental Analysis.Current edition approved July 1, 2008. Published August 2008. Originallyapproved in 1957. Last previous edition approved in 2007 as D 1492 07.2For referenced ASTM standards, visit the ASTM website, www.astm.o
14、rg, 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. Capitol St., NW, Mail Stop: SDE,
15、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.related materials. This test method gives a broad indication ofolefinic
16、content. It will not differentiate between the types ofaliphatic unsaturation.6. Apparatus6.1 Amperometric-Coulometric Apparatus, 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 Syring
17、e, 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 intended thatall reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Ch
18、emical 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 without lessening theaccuracy of the determination.7.2 Purity of WaterUnless otherwise indicated, referencesto water shal
19、l be understood to mean reagent water conformingto Type IV of Specification D 1193.7.3 Electrolyte:7.3.1 With Mercury II AcetateTo make 1 L, mix 600 mLof glacial acetic acid, 260 mL of absolute methanol, and 140mL of KBr solution (119 g/L). Dissolve2gofMercury IIacetate in this mixture.7.3.2 Without
20、 Mercury II AcetateTo make 1 L, mix 600mL of glacial acetic acid, 260 mL of absolute methanol, and140 mL of KBr solution (119 g/L).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 Mat
21、erialSafety Data Sheets, and local regulations for all materials usedin this test method.9. Sampling9.1 Sample the material in accordance with PracticeD 3437.5Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reag
22、ents 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 Titrator Circuit
23、D149208210. Procedure10.1 Place 125 mL of electrolyte in a clean, dry 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 gen
24、eration current in accor-dance with Table 1.10.2 Before introducing 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 cle
25、an 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 is kno
26、wn(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 as lon
27、g 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 and the
28、 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/100 g)
29、,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), 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. Preci
30、sion and Bias13.1 With Mercury II Acetate:13.1.1 Precision data were generated using titrators fromCentral Scientific Co. The precision obtained using titratorsfrom other suppliers has not been determined.13.1.2 PrecisionThe following data should be used forjudging the acceptability of results (95 %
31、 probability) forbromine indexes from 0 to 50:13.1.2.1 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 freedo
32、m, 61;number of cooperating laboratories, 4.13.1.3 ReproducibilityThe standard deviation is 1.43. Theresults submitted by two laboratories should be consideredsuspect if they differ by more than 4.1.13.2 Without Mercury II Acetate:13.2.1 PrecisionA ruggedness study was performed byanalyzing three sa
33、mples 20 times and one sample 5 times eachover the shortest practical time. The calculated repeatability isshown in Table 2.13.2.2 RepeatabilitySee Table 2.13.2.3 ReproducibilityTo be determined.14. Quality Guidelines14.1 Refer to Guide D 6809 for suggested QA/QC activitiesthat can be used as a part
34、 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 D 6809 tohelp ensure the quality of data generated by this test method.15. Keywords15.1 aromatic hydrocarbons; bromine index; bromine-reactive; coulometri
35、c 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 EPX 20
36、 31.2 2.9Xylene-Plant Feed 20 10.7 2.3Reformate-Feed 5 670 53.9ARepeatability = SD * 2.8.D1492083SUMMARY OF CHANGESCommittee D16.07 has identified the location of selected changes to this standard since the last issue(D 1492 - 07) that may impact the use of this standard. (Approved July 1, 2008.)(1)
37、 Updated 7.3, Electrolyte, to include the use of cell elec-trolyte with and without Mercury II Acetate.(2) Updated Section 13, Precision and Bias, to reflect therepeatability with the use of cell electrolyte with and withoutMercury II Acetate.(3) Added in 13.2.1, Precision, Table 2 which summarizes
38、therepeatability using cell electrolyte without Mercury II Acetate.(4) Updated 13.2, Precision and Bias, to follow CommitteeD16 Guidelines.Subcommittee D16.07 has identified the location of selected changes to this standard since the last issue(D 6809 - 02) that may impact the use of this standard.
39、(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 Standards.(3) Modified 3.1.1 to further clarify the definition of bromineindex (B) by adding the weight and conce
40、ntration 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 13.2.1 on QA/QC referencing GuideD 6809 specified in D16 Editorial Guidelines for Preparationand Revision of Standards.ASTM
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44、n Standards, at the address shown 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).D1492084
