ASTM D5776-2007e1 Standard Test Method for Bromine Index of Aromatic Hydrocarbons by Electrometric Titration《用电位滴定法测定芳烃溴值的标准试验方法》.pdf

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1、Designation: D 5776 07e1Standard Test Method forBromine Index of Aromatic Hydrocarbons by ElectrometricTitration1This standard is issued under the fixed designation D 5776; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year o

2、f 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.e1NOTEAn editorial correction was made in 6.1 in November 2007.1. Scope*1.1 This test method determines the amount of bromine-r

3、eactive material in aromatic hydrocarbons and is thus ameasure of trace amounts of unsaturates in these materials. It isapplicable to materials having bromine indexes below 500.1.2 This test method is applicable to aromatic hydrocarbonscontaining no more than trace amounts of olefins and that aresub

4、stantially free from material lighter than isobutane and havea distillation end point under 288C (550F).1.3 In determining the conformance of the test results usingthis method to applicable specifications, results shall berounded off in accordance with the rounding-off method ofPractice E29.1.4 The

5、values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.5 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-priat

6、e 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 1159 Test Method for Bromine Numbers of PetroleumDistillates and Commercial Aliphatic Olefins by Electro-me

7、tric TitrationD 1193 Specification for Reagent WaterD 3437 Practice for Sampling and Handling Liquid CyclicProductsD 6809 Guide for Quality Control and Quality AssuranceProcedures for Aromatic Hydrocarbons and Related Ma-terialsE29 Practice for Using Significant Digits in Test Data toDetermine Confo

8、rmance with SpecificationsE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method2.2 Other Document:OSHA Regulations, 29 CFR paragraphs 1910.1000 and1910.120033. Terminology3.1 Definition:3.1.1 bromine index, nthe number of milligrams of bro-mine consumed by

9、 100 g of sample under given conditions.4. Summary of Test Method4.1 The specimen dissolved in a specified solvent is titratedwith standard bromide-bromate solution. The end point isindicated by a fixed end-point electrometric titration apparatus,when the presence of free bromine causes a sudden cha

10、nge inthe polarization voltage of the system.5. Significance and Use5.1 This test method is suitable for setting specification, foruse as an internal quality control tool, and for use in develop-ment or research work on industrial aromatic hydrocarbons andrelated material. This test method gives a b

11、road indication ofolefinic content. It does not differentiate between the types ofaliphatic unsaturation.6. Apparatus6.1 Fixed End Point Electrometric Titration ApparatusAny fixed end-point apparatus may be used incorporating ahigh resistance polarizing current supply capable of maintain-ing approxi

12、mately 10 to 50 A across two platinum plate1This 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 Aug. 1, 2007. Published September 2007.

13、Originallyapproved in 1995. Last previous edition approved in 2006 as D 5776 99 (2006).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 Summar

14、y page onthe ASTM website.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.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbo

15、r Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.electrodes or a combination platinum electrode and with asensitivity such that a voltage change of approximately 500mV at these electrodes is sufficient to indicate the end point(see Note 1).NOTE 1The reagents and techniques may b

16、e checked by determiningthe bromine index of a 100 mg/kg cyclohexene in heptane. This isexpected to give a bromine index of 18 to 20 mg/100 g sample. Refer toTest Method D 1159 for a list of expected bromine indexes of variouscompounds.6.2 Titration VesselA tall form glass beaker of approxi-mately 2

17、50-mL capacity or a water jacketed titration vessel ofapproximately 250-mL capacity connected to a refrigeratedcirculating water bath controlling the temperature at 0 to 5C.Apair of platinum electrodes spaced not more than 5 mm apart,shall be mounted to extend well below the liquid level. Stirringsh

18、all be by a mechanical or electromagnetic stirrer and shall berapid but not so vigorous as to draw air bubbles down to theelectrodes.6.3 Iodine Number Flasks, glass-stoppered, 500-mL capac-ity.7. Reagents and Materials7.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless ot

19、herwise indicated, it is intended thatall reagents shall conform to the specifications of theAmericanChemical Society where such specifications are available.4Other grades may be used, providing it is first ascertained thatthe reagent is of sufficiently high purity to permit its usewithout lessening

20、 the accuracy of the determination.7.2 Purity of WaterUnless otherwise indicated referencesto water shall be understood to mean reagent water conformingto Type III of Specification D 1193.7.3 Bromide-Bromate Standard Solution (0.10 N)5Dissolve 10.1 g of potassium bromide (KBr) and 2.8 gpotassium bro

21、mate (KBrO3) in water and dilute to 1.0 L.Standardize to four significant figures as follows: Place 50 mLof glacial acetic acid and 1.0 mL of concentrated hydrochloricacid (HCl, sp gr 1.19) in a 500-mL iodine number flask. Chillthe solution in an ice bath for approximately 10 min and withconstant sw

22、irling of the flask, add from a 50-mL buret 40 to 45mL of bromide bromate solution, estimated to the nearest 0.01mL, at a rate such that the addition takes between 90 and 120s. Stopper the flask immediately, shake the contents, place itagain in the ice bath, and add 5.0 mL of potassium iodide (KI)so

23、lution in the lip of the flask. After 5 min remove the flaskfrom the ice bath and allow the KI solution to flow into theflask by slowly removing the stopper. Shake vigorously, add100 mL of water in such a manner as to rinse the stopper, lip,and walls of flask, and titrate promptly with the standards

24、odium thiosulphate (Na2S2O3) solution. Near the end of thetitration add 1 mL of starch indicator solution and titrate slowlyto the disappearance of the blue color.7.4 Electronic Standardization of Bromide-BromateSolutionStandardize to four significant figures as follows:Place 50 mL of glacial acetic

25、 acid and 1.0 mL of concentratedhydrochloric acid (HCl, sp gr 1.19) in a 500-mL iodine numberflask. Chill the solution in an ice bath for approximately 10 minwith constant swirling of the flask; add 4.00 mL of bromidebromate solution from the auto buret. Stopper the flaskimmediately and, shake the c

26、ontents, then cool it in an ice bathfor 5 min.Add 4.0 mL of potassium iodide (KI) to the lip of theflask, remove the flask from the ice bath and allow the KIsolution to slowly flow into the flask by removing the stopper.Shake vigorously, transfer to a chilled beaker and rinse theflask including stop

27、per with 100 mL of water. Immerse theelectrodes into the solution, titrate with standard sodiumthiosulphate (Na2S2O3) to an end point indicated by a signifi-cant change in potential that persists for 30 s (see Note 2).NOTE 2With commercial titrators, a sudden change in potentialindicated on the mete

28、r or dial of the instrument as the endpoint isapproached. When this change persists for 30 s it marks the end of thetitration. With each instrument, the manufacturers instructions should befollowed to achieve the sensitivity achieved in the platinum electrodecircuit.7.5 Potassium Iodide Solution (15

29、0 g/L)Dissolve 150 g ofpotassium iodide (KI) in water and dilute to 1.0 L.7.6 Sodium Thiosulphate, Standard Solution (0.10 N)Dissolve 25.0 g of sodium thiosulphate pentahydrate (Na2S2O35H2O) in water and add 0.02 g of sodium carbonate(Na2CO3) to stabilize the solution. Dilute to 1.0 L and mixthoroug

30、hly by shaking. Standardize by any accepted procedurethat determines the normality with an error not greater than60.0002. Restandardize at intervals frequent enough to detectchanges of 0.0005 in normality.7.7 Starch Solution6Mill5gofarrow-root starch with 3to 5 mL of water. Add the suspension to 2 L

31、 of boiling water.As a preservative, 5 to 10 mg of mercuric iodide (HgI2)or0.2g of salicylic acid can also be added. Boil for 5 to 10 min, allowto cool and then decant the clear supernatant liquid into glassstoppered bottles.7.8 Sulfuric Acid (1 + 5)Carefully add 1 volume of con-centrated sulfuric a

32、cid (H2SO4sp gr 1.84) to 5 volumes ofwater and thoroughly mix.7.9 Acetic Acid, glacial.7.10 1-Methyl-2-Pyrrolidinone.7.11 Titration SolventPrepare 1 L of titration solvent bymixing the following volumes of materials: 714 mL of glacialacetic acid, 134 mL of 1-Methyl-2-Pyrrolidinone, 134 mL ofmethanol

33、 and 18 mL of H2SO4(1 + 5).8. Hazards8.1 Consult current OSHA regulations, suppliers MaterialSafety Data Sheets, and local regulations for all materials usedin this test method.4Reagent Chemicals, American Chemical Society Specifications , AmericanChemical Society, Washington, DC. For suggestions on

34、 the testing 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.5The 0.10 N bromide-bromate standard so

35、lution is available commercially fromlaboratory chemical suppliers.6Arrow-root starch indicator solution may also be purchased prepared fromchemical suppliers.D577607e129. Sampling9.1 Sample the material in accordance with PracticeD 3437.10. Procedure10.1 Switch on the titrator and allow the electri

36、cal circuits tostabilize according to the manufacturers instructions.10.2 Introduce 150 mL of titration solvent into the titrationvessel and pipet or weigh in a quantity of sample as indicatedin Table 1 (Note 3). The sample must be completely dissolvedin the titration solvent. Switch on the stirrer

37、and adjust to arapid stirring rate, but avoid any tendency for air bubbles to bedrawn down into the solution.NOTE 3Frequently the order of magnitude of the bromine index of asample is unknown. In this case, a trial test is recommended using an 8 to10-g sample in order to obtain the approximate magni

38、tude of the bromineindex. This exploratory test should be followed with another determina-tion using the appropriate sample size as indicated in Table 1. The samplemass may be determined by obtaining the density of the sample andcalculating the mass of a measured volume.10.3 Start the titration with

39、 the bromide-bromate solutionaccording to the optimized instrument conditions. Continue thetitration until a significant change in potential persisting for 30s marks the endpoint of the titration.10.4 BlanksMake duplicate blank titrations on each batchof titration solvent and reagents. Make sure tha

40、t less than 0.10mL of bromide-bromate solution is required.11. Calculations11.1 Calculate the normality of the bromide-bromate solu-tion as follow:N15 A2N2/A1(1)where:N1= normality of the bromide-bromate solution,A1= volume of bromide-bromate solution, mL,A2=Na2S2O3solution required for titration of

41、 thebromide-bromate solution, mL, andN2= normality of the Na2S2O3solution.11.2 Calculate the bromine index as follows:Bromine index 5 A 2 B!N 3 7990/W (2)where:A = volume of bromide-bromate solution required fortitration of the sample, mL,B = volume of bromide-bromate solution required fortitration

42、of the blank, mL,N = normality of bromide-bromate solution,W = amount of sample, g, and7990 = molecular weight of bromine 3 100.12. Report12.1 Report the following information:12.1.1 Bromine index to the nearest 0.5 mg/100 g.13. Precision and Bias713.1 PrecisionThe following criteria should be used

43、tojudge the acceptability at the 95 % probability level of theresults obtained by this test method. The precision criteria werederived from an interlaboratory study between 7 laboratoriesconducted in accordance with Practice E 691.13.2 RepeatabilityResults in the same laboratory shouldnot be conside

44、red suspect unless they differ by more than plusor minus the amount shown in Table 2.13.3 ReproducibilityResults submitted by two laborato-ries should not be considered suspect unless they differ bymore than plus or minus the amount shown in Table 2.13.4 BiasSince there is no acceptable reference ma

45、terialsuitable for determining the bias in this test method formeasuring bromine index in aromatic hydrocarbons, bias hasnot been determined.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 oper

46、ator 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; electrometric titration7Supporting data have been filed at ASTM

47、International Headquarters and maybe obtained by requesting Research Report RR: D16-1026.TABLE 1 Sample SizeBromine Index Sample Size, g0to20 5020 to 100 30 to 40100 to 200 20 to 30200 to 500 8 to 10TABLE 2 Bromine Index Repeatability and ReproducibilityConcentration, mg Bromine /100 g Repeatability

48、 Reproducibility7.5 1.1 4.620 1.6 4.325 2.1 3.635 2.0 11.5D577607e13SUMMARY OF CHANGESCommittee D16 has identified the location of selected changes to this standard since the last issue(D 5776 - 99 (2006) that may impact the use of this standard. (Approved August 1, 2007.)(1) Changed 1.3 to “In dete

49、rmining the conformance of thetest results using this method to applicable specifications,results shall be rounded off in accordance with the rounding-offmethod of Practice E29” as deemed mandatory in CommitteeD16 Editorial Guidelines.(2) Updated 2.1 to add reference to Guide D 6809.(3) Updated Sections 1 through 15 to replace “a” with “an”where warranted.(4) Added the terms “volume of,” “amount of,” “normality,”and “molecular” to the description of the variables use in thecalculations.(5) Added Section 14, Quality Guidelines on QA/QC refer-encing Gu