1、Designation: D5776 14Standard Test Method forBromine Index of Aromatic Hydrocarbons by ElectrometricTitration1This standard is issued under the fixed designation D5776; 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 determines the amount of bromine-reactive material in aromatic hydrocarbons and is thus ameasure of tr
3、ace amounts of unsaturates in these materials. It isapplicable to materials having bromine indexes below 35.Materials with a higher bromine index can be analyzed by thismethod; however, the precision section does not apply.1.2 This test method is applicable to aromatic hydrocarbonscontaining no more
4、 than trace amounts of olefins and that aresubstantially free from material lighter than isobutane and havea distillation end point under 288C.1.3 In determining the conformance of the test results usingthis method to applicable specifications, results shall berounded off in accordance with the roun
5、ding-off method ofPractice 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 purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of
6、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 8.2. Referenced Documents2.1 ASTM Standards:2D1159 Test Method for Bromine Numbers of PetroleumDistillates and Comme
7、rcial Aliphatic Olefins by Electro-metric TitrationD1193 Specification for Reagent WaterD3437 Practice for Sampling and Handling Liquid CyclicProductsD6809 Guide for Quality Control and Quality AssuranceProcedures for Aromatic Hydrocarbons and Related Ma-terialsE29 Practice for Using Significant Dig
8、its 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 CFR paragraphs 1910.1000 and1910.120033. Terminology3.1 Definitions:3.1.1 bromine index, nthe number of
9、milligrams of bro-mine consumed by 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 o
10、f free bromine causes a sudden change 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 ma
11、terial. This test method gives a broad 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 supp
12、ly capable of maintain-ing approximately 1 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 Feb. 15
13、, 2014. Published February 2014. Originallyapproved in 1995. Last previous edition approved in 2013 as D5776 13. DOI:10.1520/D5776-14.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume info
14、rmation, refer to the standards Document Summary 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.*A Summary of Changes section appears at the end of this standar
15、dCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1electrodes 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 No
16、te 1).NOTE 1The reagents and techniques may be 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 D1159 for a list of expected bromine indexes of variouscompounds.6.2 Titration Vessel
17、A tall form glass beaker of approxi-mately 250-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 ex
18、tend well below the liquid level. Stirringshall 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 ch
19、emicals shall beused in all tests. Unless otherwise 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 hi
20、gh purity to permit its usewithout lessening 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 D1193.7.3 Bromide-Bromate Standard Solution (0.10 N)5Dissolve 10.1 g of pot
21、assium bromide (KBr) and 2.8 gpotassium bromate (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 f
22、or approximately 10 min and withconstant swirling 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
23、, and add 5.0 mL of potassium iodide (KI)solution 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 fla
24、sk, and titrate promptly with the standardsodium thiosulphate (Na2S2O3) solution. Near the end of thetitration add 1 mLof starch indicator solution and titrate slowlyto the disappearance of the blue color.7.4 Electronic Standardization of Bromide-BromateSolutionStandardize to four significant figure
25、s as follows:Place 50 mL of glacial acetic acid and 1.0 mL of concentratedhydrochloric acid (HCl, sp gr 1.19) in a 500-mLiodine 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. Stop
26、per the flaskimmediately and, shake the contents, then cool it in an ice bathfor 5 min.Add 4.0 mLof 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
27、beaker and rinse theflask including stopper 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
28、change in potentialindicated on the meter 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 electrodec
29、ircuit.7.5 Potassium Iodide Solution (150 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 s
30、olution. Dilute to 1.0 L and mixthoroughly 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
31、 mL of water. Add the suspension to 2 L 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 a
32、dd 1 volume of con-centrated sulfuric acid (H2SO4sp gr 1.84) to 5 volumes ofwater and thoroughly mix.7.9 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 and 18 mL of H2S
33、O4(1 + 5).NOTE 3Dichloromethane, 1,1,1-trichloroethane, carbon tetrachlorideor chloroform can be used to replace 1-methyl-2-pyrrolidinone in thetitration solvent to improve miscibility with the sample.4Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington,
34、 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 States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.5The 0.10 N brom
35、ide-bromate standard solution is available commercially fromlaboratory chemical suppliers.6Arrow-root starch indicator solution may also be purchased prepared fromchemical suppliers.D5776 1428. Hazards8.1 Consult current OSHA regulations, suppliers MaterialSafety Data Sheets, and local regulations f
36、or all materials usedin this test method.9. Sampling9.1 Sample the material in accordance with Practice D3437.10. Procedure10.1 Switch on the titrator and allow the electrical circuits tostabilize according to the manufacturers instructions.10.2 Introduce 150 mL of titration solvent into the titrati
37、onvessel and pipet or weigh in a quantity of sample as indicatedin Table 1 (Note 4). The sample must be completely dissolvedin the titration solvent. Switch on the stirrer and adjust to arapid stirring rate, but avoid any tendency for air bubbles to bedrawn down into the solution.NOTE 4Frequently th
38、e 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 magnitude of the bromineindex. This exploratory test should be followed with another determina-tion using the appropriate sample size
39、 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 the bromide-bromate solutionaccording to the optimized instrument conditions. Continue thetitration until a significant change
40、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 that less than 0.10mL of bromide-bromate solution is required.11. Calculations11.1 Calculate the normality of the bromide-bromate s
41、olu-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 the bromide-bromate solution, mL, andN2= normality of the Na2S2O3solution.11.2 Calculate the bromine index as follows:Bromine i
42、ndex 5 A 2 B!N 37990#/W (2)where:A = volume of bromide-bromate solution required fortitration of the sample, mL,B = volume of bromide-bromate solution required fortitration of the blank, mL,N = normality of bromide-bromate solution,W = amount of sample, g, and7990 = molecular weight of bromine 100.1
43、2. 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 tojudge the acceptability at the 95 % probability level of theresults obtained by this test method. The precision criteria werede
44、rived from an interlaboratory study between 7 laboratoriesconducted in accordance with Practice E691.13.2 RepeatabilityResults in the same laboratory shouldnot be considered suspect unless they differ by more than plusor minus the amount shown in Table 2.13.3 ReproducibilityResults submitted by two
45、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 materialsuitable for determining the bias in this test method formeasuring bromine index in aromatic hydrocarbons, bias hasnot been
46、determined.14. Quality Guidelines14.1 Refer to Guide D6809 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 performrelevant QA/QC activities like the ones in Guide D6809 to helpensure the quality of data
47、 generated by this test method.15. Keywords15.1 aromatic hydrocarbons; bromine index; bromine-reactive; electrometric titration7Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D16-1026. ContactASTM CustomerService at serviceastm.
48、org.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 Reproducibility7.5 1.1 4.620 1.6 4.325 2.1 3.635 2.0 11.5D5776 143SUMMARY OF CHANGES
49、Committee D16 has identified the location of selected changes to this standard since the last issue (D577613)that may impact the use of this standard. (Approved February 15, 2014.)(1) Updated Note 3.Committee D16 has identified the location of selected changes to this standard since the last issue(D577607(2012) that may impact the use of this standard. (Approved July 15, 2013.)(1) Updated Scope in Section 1.1 to reflect the full precisionstatement.(2) Updated Section 6.1.(3) Deleted Section 7.10.(4) Added Note 3 to renumbered Section 7.11.ASTM
