ASTM D3341-2005 Standard Test Method for Lead in Gasoline-Iodine Monochloride Method《汽油中铅含量的标准试验方法 单氯化碘法》.pdf

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1、Designation: D 3341 05An American National StandardStandard Test Method forLead in GasolineIodine Monochloride Method1This standard is issued under the fixed designation D 3341; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the y

2、ear of 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.1. Scope*1.1 This test method determines total lead in gasolinescontaining lead alkyls at concentrations between 0.026 and

3、 1.3g Pb/L, and 0.12 and 6.0 g Pb/UK gal, 0.1 and 5.0 g Pb/US gal.1.2 The preferred units are grams per litre although bothgram per US gallon and grams per UK gallon are acceptabledue to their widespread use in the industry.1.3 This standard does not purport to address all of thesafety concerns, if

4、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 specific hazardstatements, see Sections 6 and 8.2. Referenced Documents2.1 ASTM Standa

5、rds:2D 1193 Specification for Reagent WaterD 4057 Practice for Manual Sampling of Petroleum andPetroleum ProductsD 6299 Practice for Applying Statistical Quality AssuranceTechniques to Evaluate Analytical Measurement SystemPerformance3. Summary of Test Method3.1 A known volume of the sample is dilut

6、ed with heavydistillate and shaken with aqueous iodine monochloride re-agent. Any tetraalkyl lead compounds present react with theiodine monochloride and are extracted into the aqueous phaseas the dialkyl lead compounds. The aqueous extract is sepa-rated from the gasoline and evaporated to low bulk

7、to decom-pose free iodine monochloride. Any organic matter present isremoved by oxidation with nitric acid, which also serves toconvert the dialkyl lead compounds into inorganic lead com-pounds. The residue is dissolved in distilled water and bufferedto pH 5 using sodium acetate-acetic acid buffer.

8、The leadcontent of the buffered solution is determined by titration withEDTA using xylenol orange as indicator.4. Significance and Use4.1 This test method determines the concentration of leadalkyl additives in gasoline. These additives improve the anti-knock properties.5. Apparatus5.1 Separatory Fun

9、nel, borosilicate glass, capacity 250 mL,glass-stoppered with preferably an iodine flask type of neck.5.2 Erlenmeyer Flask, borosilicate glass, capacity 500 mL.6. Reagents and Materials6.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended

10、 thatall reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.3Other grades may beused, provided it is first ascertained that the reagent is ofsufficiently high purity to permit its use without

11、lessening theaccuracy of the determination.6.1.1 Commercially available reagents may be used in placeof laboratory preparations when they conform to the specifi-cations in 6.1.6.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean reagent water as definedby Typ

12、e III or Type IV of Specification D 1193.6.3 Ammonia Solution (1 + 1)Mix 1 volume of concen-trated ammonia solution (rel dens 0.90) with 1 volume ofdistilled water.6.4 Bromthymol Blue Indicator Solution Dissolve 0.1 g ofbromthymol blue in 50 mL of ethanol and dilute to 100 mLwith distilled water.6.5

13、 EDTA, Standard Solution (0.005 M)Dissolve approxi-mately 3.75 g of diaminoethanetetra-acetic acid, disodium salt,in 2-L of distilled water. Determine the molarity of the solutionby standardization with lead nitrate solution as follows:1This test method is under the jurisdiction of ASTM Committee D0

14、2 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.03 on Elemental Analysis.Current edition approved May 1, 2005. Published May 2005. Originallyapproved in 1974. Last previous edition approved in 2000 as D 334100.2For referenced ASTM standards, visit the ASTM w

15、ebsite, 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 ASTM website.3Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For s

16、uggestions 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.1*A Summary of Changes sec

17、tion appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.6.5.1 Using a pipet, transfer 25.0 mL of the standard leadnitrate solution to a 250-mL Erlenmeyer flask. Dilute to about75 mL with distilled wate

18、r and add several drops of bromthy-mol blue indicator solution. Titrate with 1 + 1 ammonia solu-tion until the color of the solution just changes to blue; then add10 mLof sodium acetate-acetic acid buffer solution and 5 dropsof xylenol orange indicator solution. In the presence of lead thesolution w

19、ill have a rose color. Titrate with the EDTA solution.The color changes near the end point, this being indicated by asharp change from orange to a permanent bright lemon-yellow.6.5.2 Record the titer and calculate the molarity of theEDTA solution. The addition of excess EDTA produces nofurther color

20、 change at the end point.6.6 Heavy DistillateA straight-run, lead-free, petroleumdistillate of low bromine number, with approximately 10 %distilling at 400F (205C) and 90 % at 460F (240C)(WarningCombustible).6.7 Iodine Monochloride Reagent (1.0 M) (WarningIodine monochloride will react with ammonium

21、 ions undercertain conditions to yield nitrogen triiodide, which is explo-sive. Take care, therefore, that this reagent does not come intocontact with ammonia or ammonium salts.) Dissolve 111.0 g ofpotassium iodide (KI) in approximately 400 mL of distilledwater. Add 445 mL of concentrated hydrochlor

22、ic acid (sp gr1.18) and cool to room temperature. Add 75.0 g of potassiumiodate (KIO3) slowly and with stirring, until all the free iodineinitially formed has just redissolved to give a clear orange-redsolution (the amounts of KI and KIO3are calculated to give aslight excess of iodate; if a greater

23、excess is present, this willcause precipitation of lead and indifferent end points in theEDTA titration). Cool to room temperature and dilute to 1 Lwith distilled water. Store in a glass-stoppered bottle(WarningDo not use rubber stoppers to stopper vesselscontaining iodine monochloride solutions.).6

24、.8 Lead Nitrate, Standard Solution (0.005 M)Weigh withan accuracy of 60.001 g about 1.7 g of lead nitrate (Pb(NO3)2)that has been dried at 105C and cooled in a desiccator.Dissolve it in distilled water and add 10 mL of concentratednitric acid. Dilute to 1 L with distilled water in a volumetricflask

25、and shake thoroughly to mix. Calculate the molarity ofthe solution according to the equation:Molarity 5 wt g! of lead nitrate/331.23 (1)6.9 Nitric Acid, concentrated (rel dens 1.42).6.10 Sodium Acetate, Acetic Acid Buffer SolutionDissolve23.0 g of anhydrous sodium acetate in about 500 mL ofdistilled

26、 water. Using a buret, add 6.2 mL of glacial acetic acid.Dilute to 1 L with distilled water in a 1-L volumetric flask andshake to mix.6.11 Xylenol Orange Indicator Solution Dissolve 0.2 g ofxylenol orange, sodium salt, in 100 mL of distilled water andadd 1 drop of 1 + 1 hydrochloric acid. (Prepare f

27、reshly eachweek.)7. Sampling7.1 Samples shall be taken in accordance with the instruc-tions in Practice D 4057.8. Procedure8.1 Transfer 50 mL of the iodine monochloride reagent and25 mL of heavy distillate to the 250-mL separatory funnel.Measure the temperature of the sample to the nearest 0.5C(1F)

28、(Note 1). Using a pipet (WarningNever suck leadedgasoline or corrosive liquids into a pipet by the mouth),transfer 25 6 0.05 mL of the sample of the gasoline to theseparatory funnel. Immediately stopper the funnel and shakethe contents for 60 s. Allow the funnel to stand for severalminutes, until th

29、e two phases have separated and run the loweraqueous phase into a 500-mL Erlenmeyer flask made ofborosilicate glass. Wash the gasoline phase by shaking withthree separate 20-mL portions of distilled water and add thewashings to the Erlenmeyer flask.NOTE 1For cool gasolines having a Reid vapor pressu

30、re above 7.0 lbcool the sealed sample container to approximately 60F (15C) beforeremoving the sample for analysis.8.2 Place several glass beads in the flask, cover the mouth ofthe flask with a small ribbed watch glass, and place on a hotplate. Heat the contents and allow to boil until the volume oft

31、he solution is 15 to 20 mL. Without removing the flask fromthe hot plate, add 5 mL of concentrated nitric acid down theside of the flask and evaporate the contents almost to drynessto oxidize any organic material present. Repeat the nitric acidtreatment, evaporating almost to dryness until all the o

32、rganicmatter has been removed and a white residue remains. Finallyremove the watch glass and evaporate the solution to dryness.Remove the flask from the hot plate and allow the contents tocool.8.3 Add about 200 mL of distilled water to the flask andswirl to dissolve the residue. The residue may be q

33、uicklydissolved by heating the solution, but this must be cooledbefore titrating. Add 5 drops of bromthymol blue indicator andtitrate with 1 + 1 ammonia solution until the color just changesto blue; then add 10 mL of sodium acetate-acetic acid buffersolution and 5 drops of xylenol orange indicator s

34、olution. Inthe presence of lead, the solution will now have a rose color.8.4 Titrate with the 0.005 M standard EDTA solution. Thecolor of the solution changes to orange near the end point, theend point being indicated by a sharp change from orange to apermanent bright lemon-yellow. Note the titer. T

35、he addition ofexcess EDTA solution produces no further color change at theend point.8.5 Carry out a blank determination on the reagents, exclud-ing the heavy distillate and omitting the extraction stage and, ifnecessary, correct the sample titer accordingly.9. Calculation9.1 Calculate the concentrat

36、ion of lead by means of one ofthe following equations (see also Note 2):Lead, g/US gal at 60F 15.5C!5 31.37 TM 1 1 0.00065 t 2 60!(2)D3341052Lead, g/UK gal at 60 F 15.5C!5 37.68 TM 1 1 0.00065 t 2 60!(3)Lead, g/L at 15C 5 8.288 TM 1 1 0.0012 tx2 15! (4)where:T = volume of EDTA solution used to titra

37、te the sample,mL,M = molarity of EDTA solution,t = the temperature of gasoline when pipeting sample, F,andtx= temperature of gasoline when pipeting sample, C.NOTE 2The constant 31.37 is obtained from the expression0.20721 3 3785.3/25, where 0.20721 is the number of grams of leadequivalent to 1 mL of

38、 M EDTA solution, 3785.3 is the number ofmillilitres in a US gal, and 25 represents the sample volume in millilitres.The constant 37.68 is obtained by multiplying 31.37 by 1.201 (the ratio ofmillilitres in 1 UK gal to millilitres in 1 US gal, 4546.0 and 3785.3respectively). The constant 8.288 is obt

39、ained by dividing 31.37 by 3.7853.NOTE 3The coefficient of expansion of gasolines is taken as0.00065/C at 60F and 0.0012/C at 15C.NOTE 4For gasoline containing only tetraethyl-lead (TEL) ortetramethyl-lead (TML), the grams of lead per unit volume can beconverted to millilitres per unit volume by mul

40、tiplying by the followingfactors:For tetraethyl lead TEL!50.946 (5)For tetramethyl lead TML!50.64810. Quality Control10.1 Confirm the performance of the test procedure byanalyzing a quality control sample that is stable and represen-tative of the sample of interest.10.1.1 When the quality control/qu

41、ality assurance protocolsare already established in the testing facility, these may be usedto confirm the reliability of the test reult.10.1.2 When there is no quality control/quality assuranceprotocol established in the testing facility, Appendix X1 can beused to perform this function.11. Report11.

42、1 Report the result to the nearest 0.01 g Pb/US gal at60F, 0.01 g Pb/UK gal at 60F, or 0.002 g Pb/L at 15C, asappropriate.12. Precision and Bias12.1 PrecisionThe precision of the method as determinedby statistical examination of interlaboratory test results is asfollows:12.1.1 RepeatabilityThe diffe

43、rence between two test re-sults, obtained by the same operator with the same apparatusunder constant operating conditions on identical test material,would in the long run, in the normal and correct operation ofthe test method, exceed the following values only in one casein twenty:Litre: 0.00365 1 0.

44、0073A2(6)where:A2= the average of the results in grams of lead per litre at15.5C.US gallon: 0.0138 1 0.0073A (7)where:A = the average of the results in grams of lead per USgallon at 60F (15.5C)UK gallon: 0.0166 1 0.0073A1(8)where:A1= the average of the results in grams of lead per UKgallon at 60F (1

45、5.5C)12.1.2 ReproducibilityThe difference between two singleand independent results obtained by different operators work-ing in different laboratories on identical test material would, inthe long run, in the normal and correct operation of the testmethod, exceed the following values only in one case

46、 intwenty:Litre: 0.0135 1 0.027A2(9)where:A2= the average of the results in grams of lead per litre at15.5C.UK gallon: 0.0613 1 0.027A1(10)A1= the average of the results in grams of lead per UKgallon at 60F (15.5C)US gallon: 0.0511 1 0.027A (11)where:A = the average of the results in grams of lead p

47、er USgallon at 60F (15.5C)NOTE 5The above precision was obtained in an ISO cooperative testprogram on samples covering a range from 1.0 to 3.3 g Pb/US gal. In asubsequent ASTM testing program the range was extended down to 0.1 gPb/US gal with equal or better precision. Although no samples with leadc

48、oncentrations, as high as the 5.0 g Pb/US gal specified in the Scope weretested, there is no obvious reason why the method should not be equallysatisfactory at that concentration.NOTE 6In the cooperative test program from which the aboveprecision was obtained, dimethyl yellow was used as the indicat

49、or.12.1.3 BiasIt is not practicable to specify the bias of thistest method for measuring lead because the responsible sub-committee, after diligent search, was unable to attract volun-teers for an interlaboratory study.13. Keywords13.1 gasoline; iodine monochloride; leadD3341053APPENDIX(Nonmandatory Information)X1. QUALITY CONTROLX1.1 Confirm the performance of the instrument or the testprocedure by analyzing a quality control (QC) sample.X1.2 Prior to monitoring the measurement process, the userof the method needs