1、Designation: D5776 07 (Reapproved 2012)D5776 13Standard 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 o
2、f revision, the year of last 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
3、and is thus a measure oftrace amounts of unsaturates in these materials. It is applicable to materials having bromine indexes below 500.35. Materials witha higher bromine index can be analyzed by this method; however, the precision section does not apply.1.2 This test method is applicable to aromati
4、c hydrocarbons containing no more than trace amounts of olefins and that aresubstantially free from material lighter than isobutane and have a distillation end point under 288C (550F).288C.1.3 In determining the conformance of the test results using this method to applicable specifications, results
5、shall be roundedoff in accordance with the rounding-off method of Practice E29.1.4 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for informationonly.standard. No other units of measurement are included in this standard.1.5 This standard does no
6、t purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use. For a specific hazard statement see Secti
7、on 8.2. Referenced Documents2.1 ASTM Standards:2D1159 Test Method for Bromine Numbers of Petroleum Distillates and CommercialAliphatic Olefins by Electrometric TitrationD1193 Specification for Reagent WaterD3437 Practice for Sampling and Handling Liquid Cyclic ProductsD6809 Guide for Quality Control
8、 and Quality Assurance Procedures for Aromatic Hydrocarbons and Related MaterialsE29 Practice for Using Significant Digits in Test Data to Determine Conformance with SpecificationsE691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method2.2 Other Document:OSHA
9、 Regulations, 29 CFR paragraphs 1910.1000 and 1910.120033. Terminology3.1 Definitions:3.1.1 bromine index, nthe number of milligrams of bromine consumed by 100 g of sample under given conditions.4. Summary of Test Method4.1 The specimen dissolved in a specified solvent is titrated with standard brom
10、ide-bromate solution. The end point is indicatedby a fixed end-point electrometric titration apparatus, when the presence of free bromine causes a sudden change in the polarizationvoltage of the system.1 This test method is under the jurisdiction of ASTM Committee D16 on Aromatic Hydrocarbons and Re
11、lated Chemicals and is the direct responsibility of SubcommitteeD16.04 on Instrumental Analysis.Current edition approved Jan. 1, 2012July 15, 2013. Published January 2012July 2013. Originally approved in 1995. Last previous edition approved in 20072012 asD5776 07 (2012). 1. DOI: 10.1520/D5776-07R12.
12、 10.1520/D5776-13.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 Available from U.S. Government Printing O
13、ffice Superintendent of Documents, 732 N. Capitol St., NW, Mail Stop: SDE, Washington, DC 20401, http:/www.access.gpo.gov.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit
14、 may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*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 suitable for setting specification, for use as an internal quality control tool, and for use in developmentor rese
16、arch work on industrial aromatic hydrocarbons and related material. This test method gives a broad indication of olefiniccontent. It does not differentiate between the types of aliphatic unsaturation.6. Apparatus6.1 Fixed End Point Electrometric Titration ApparatusAny fixed end-point apparatus may b
17、e used incorporating a highresistance polarizing current supply capable of maintaining approximately 101 to 50 A across two platinum plate electrodes ora combination platinum electrode and with a sensitivity such that a voltage change of approximately 500 mV at these electrodesis sufficient to indic
18、ate the end point (see Note 1).NOTE 1The reagents and techniques may be checked by determining the bromine index of a 100 mg/kg cyclohexene in heptane. This is expectedto give a bromine index of 18 to 20 mg/100 g sample. Refer to Test Method D1159 for a list of expected bromine indexes of various co
19、mpounds.6.2 Titration VesselA tall form glass beaker of approximately 250-mL capacity or a water jacketed titration vessel ofapproximately 250-mL capacity connected to a refrigerated circulating water bath controlling the temperature at 0 to 5C. A pairof platinum electrodes spaced not more than 5 mm
20、 apart, shall be mounted to extend well below the liquid level. Stirring shall beby a mechanical or electromagnetic stirrer and shall be rapid but not so vigorous as to draw air bubbles down to the electrodes.6.3 Iodine Number Flasks, glass-stoppered, 500-mL capacity.7. Reagents and Materials7.1 Pur
21、ity of ReagentsReagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that allreagents shall conform to the specifications of the American Chemical Society where such specifications are available.4 Othergrades may be used, providing it is first ascertained tha
22、t the reagent is of sufficiently high purity to permit its use without lesseningthe accuracy of the determination.7.2 Purity of WaterUnless otherwise indicated references to water shall be understood to mean reagent water conforming toType III of Specification D1193.7.3 Bromide-Bromate Standard Solu
23、tion (0.10 N)5Dissolve 10.1 g of potassium bromide (KBr) and 2.8 g potassium bromate(KBrO3) in water and dilute to 1.0 L. Standardize to four significant figures as follows: Place 50 mL of glacial acetic acid and 1.0mL of concentrated hydrochloric acid (HCl, sp gr 1.19) in a 500-mL iodine number fla
24、sk. Chill the solution in an ice bath forapproximately 10 min and with constant swirling of the flask, add from a 50-mL buret 40 to 45 mL of bromide bromate solution,estimated to the nearest 0.01 mL, at a rate such that the addition takes between 90 and 120 s. Stopper the flask immediately, shakethe
25、 contents, place it again in the ice bath, and add 5.0 mL of potassium iodide (KI) solution in the lip of the flask. After 5 minremove the flask from the ice bath and allow the KI solution to flow into the flask by slowly removing the stopper. Shakevigorously, add 100 mL of water in such a manner as
26、 to rinse the stopper, lip, and walls of flask, and titrate promptly with thestandard sodium thiosulphate (Na2S2O3) solution. Near the end of the titration add 1 mL of starch indicator solution and titrateslowly to the disappearance of the blue color.7.4 Electronic Standardization of Bromide-Bromate
27、 SolutionStandardize to four significant figures as follows: Place 50 mLof glacial acetic acid and 1.0 mL of concentrated hydrochloric acid (HCl, sp gr 1.19) in a 500-mL iodine number flask. Chill thesolution in an ice bath for approximately 10 min with constant swirling of the flask; add 4.00 mLof
28、bromide bromate solution fromthe auto buret. Stopper the flask immediately and, shake the contents, then cool it in an ice bath for 5 min.Add 4.0 mLof potassiumiodide (KI) to the lip of the flask, remove the flask from the ice bath and allow the KI solution to slowly flow into the flask byremoving t
29、he stopper. Shake vigorously, transfer to a chilled beaker and rinse the flask including stopper with 100 mL of water.Immerse the electrodes into the solution, titrate with standard sodium thiosulphate (Na2S2O3) to an end point indicated by asignificant change in potential that persists for 30 s (se
30、e Note 2).NOTE 2With commercial titrators, a sudden change in potential indicated on the meter or dial of the instrument as the endpoint is approached. Whenthis change persists for 30 s it marks the end of the titration. With each instrument, the manufacturers instructions should be followed to achi
31、eve thesensitivity achieved in the platinum electrode circuit.7.5 Potassium Iodide Solution (150 g/L)Dissolve 150 g of potassium 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 a
32、dd 0.02 g of sodium carbonate (Na2CO3) to stabilize the solution. Dilute to 1.0 L and mix thoroughly by shaking.Standardize by any accepted procedure that determines the normality with an error not greater than 60.0002. Restandardize atintervals frequent enough to detect changes of 0.0005 in normali
33、ty.4 Reagent Chemicals, American Chemical Society Specifications, American Chemical Society, Washington, DC. For suggestions on the testing of reagents not listed bythe American Chemical Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Phar
34、macopeia and NationalFormulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville, MD.5 The 0.10 N bromide-bromate standard solution is available commercially from laboratory chemical suppliers.D5776 1327.7 Starch Solution6Mill 5 g of arrow-root starch with 3 to 5 mL of water. Add the suspension
35、 to 2 L of boiling water. Asa preservative, 5 to 10 mg of mercuric iodide (HgI2) or 0.2 g of salicylic acid can also be added. Boil for 5 to 10 min, allow tocool and then decant the clear supernatant liquid into glass stoppered bottles.7.8 Sulfuric Acid (1 + 5)Carefully add 1 volume of concentrated
36、sulfuric acid (H2SO4 sp gr 1.84) to 5 volumes of water andthoroughly mix.7.9 Acetic Acid, glacial.7.10 1-Methyl-2-Pyrrolidinone.7.9 Titration SolventPrepare 1 L of titration solvent by mixing the following volumes of materials: 714 mL of glacial aceticacid, 134 mL of 1-Methyl-2-Pyrrolidinone, 134 mL
37、 of methanol and 18 mL of H2SO4 (1 + 5).NOTE 3Dichloromethane, 1,1,1-trichloroethane or carbon tetrachloride can be used to replace 1-methyl-2-pyrrolidinone in the titration solvent toimprove miscibility with the sample.8. Hazards8.1 Consult current OSHA regulations, suppliers Material Safety Data S
38、heets, and local regulations for all materials used inthis 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 to stabilize according to the manufacturersmanufacturersinstructions.10.2 Introduce 1
39、50 mL of titration solvent into the titration vessel and pipet or weigh in a quantity of sample as indicated inTable 1 (Note 34). The sample must be completely dissolved in the titration solvent. Switch on the stirrer and adjust to a rapidstirring rate, but avoid any tendency for air bubbles to be d
40、rawn down into the solution.NOTE 4Frequently the order of magnitude of the bromine index of a sample is unknown. In this case, a trial test is recommended using an 8 to 10-gsample in order to obtain the approximate magnitude of the bromine index. This exploratory test should be followed with another
41、 determination usingthe appropriate sample size as indicated in Table 1. The sample mass may be determined by obtaining the density of the sample and calculating the massof a measured volume.10.3 Start the titration with the bromide-bromate solution according to the optimized instrument conditions.
42、Continue thetitration until a significant change in potential persisting for 30 s marks the endpoint of the titration.10.4 BlanksMake duplicate blank titrations on each batch of titration solvent and reagents. Make sure that less than 0.10 mLof bromide-bromate solution is required.11. Calculations11
43、.1 Calculate the normality of the bromide-bromate solution as follow:N15A 2N2/A1 (1)where:N1 = normality of the bromide-bromate solution,A1 = volume of bromide-bromate solution, mL,A2 = Na2S2O3 solution required for titration of the bromide-bromate solution, mL, andN2 = normality of the Na2S2O3 solu
44、tion.11.2 Calculate the bromine index as follows:Bromine index5A 2B!N 37990#/W (2)6 Arrow-root starch indicator solution may also be purchased prepared from chemical suppliers.TABLE 1 Sample SizeBromine Index Sample Size, g0 to 20 5020 to 100 30 to 40100 to 200 20 to 30200 to 500 8 to 10D5776 133whe
45、re:A = volume of bromide-bromate solution required for titration of the sample, mL,B = volume of bromide-bromate solution required for titration of the blank, mL,N = normality of bromide-bromate solution,W = amount of sample, g, and7990 = molecular weight of bromine 100.12. Report12.1 Report the fol
46、lowing 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 to judge the acceptability at the 95 % probability level of the resultsobtained by this test method. The precision criteria were derived from an interlaborat
47、ory study between 7 laboratories conductedin accordance with Practice E691.13.2 RepeatabilityResults in the same laboratory should not be considered suspect unless they differ by more than plus orminus the amount shown in Table 2.13.3 ReproducibilityResults submitted by two laboratories should not b
48、e considered suspect unless they differ by more thanplus or minus the amount shown in Table 2.13.4 BiasSince there is no acceptable reference material suitable for determining the bias in this test method for measuringbromine index in aromatic hydrocarbons, bias has not been determined.14. Quality G
49、uidelines14.1 Refer to Guide D6809 for suggested QA/QC activities that can be used as a part of this test method. It is recommendedthat the operator of this test method select and perform relevant QA/QC activities like the ones in Guide D6809 to help ensurethe quality of data generated by this test method.15. Keywords15.1 aromatic hydrocarbons; bromine index; bromine-reactive; electrometric titrationSUMMARY OF CHANGESCommittee D16 has identified the location of selected changes to this standard since the last issue (D5776 - 99(2006)D5776) 0
