1、Designation: D3227 04a (Reapproved 2010)Designation: 342/00Standard Test Method for(Thiol Mercaptan) Sulfur in Gasoline, Kerosine, AviationTurbine, and Distillate Fuels (Potentiometric Method)1This standard is issued under the fixed designation D3227; the number immediately following the designation
2、 indicates the year oforiginal adoption or, in the case of 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.This standard has been approved for use by agenci
3、es of the Department of Defense.1. Scope1.1 This test method covers the determination of mercaptansulfur in gasolines, kerosines, aviation turbine fuels, anddistillate fuels containing from 0.0003 to 0.01 mass % ofmercaptan sulfur. Organic sulfur compounds such as sulfides,disulfides, and thiophene,
4、 do not interfere. Elemental sulfur inamounts less than 0.0005 mass % does not interfere. Hydrogensulfide will interfere if not removed, as described in 9.2.1.2 The values in acceptable SI units are to be regarded asthe standard. The values in parentheses are for informationonly.1.3 This standard do
5、es 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-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. For specificwarning statements, se
6、e Sections 6, 8, 9, and Appendix X1.2. Referenced Documents2.1 ASTM Standards:2D1193 Specification for Reagent WaterD1250 Guide for Use of the Petroleum Measurement TablesD1298 Test Method for Density, Relative Density (SpecificGravity), or API Gravity of Crude Petroleum and LiquidPetroleum Products
7、 by Hydrometer MethodD4052 Test Method for Density, Relative Density, and APIGravity of Liquids by Digital Density MeterD4057 Practice for Manual Sampling of Petroleum andPetroleum ProductsD4177 Practice for Automatic Sampling of Petroleum andPetroleum ProductsD6299 Practice for Applying Statistical
8、 Quality Assuranceand Control Charting Techniques to Evaluate AnalyticalMeasurement System Performance3. Summary of Test Method3.1 The hydrogen sulfide-free sample is dissolved in analcoholic sodium acetate titration solvent and titrated potentio-metrically with silver nitrate solution, using as an
9、indicator thepotential between a glass reference electrode and a silver/silver-sulfide indicating electrode. Under these conditions, themercaptan sulfur is precipitated as silver mercaptide and theend point of the titration is shown by a large change in cellpotential.4. Significance and Use4.1 Merca
10、ptan sulfur has an objectionable odor, an adverseeffect on fuel system elastomers, and is corrosive to fuelsystem components.5. Apparatus5.1 As described in 5.2-5.5; alternatively, any automatictitration system may be used that, using the same electrode pairdescribed in 5.3, is capable of performing
11、 the titration asdescribed in Section 9 and selecting the endpoint specified in11.1 with a precision that meets or is better than that given inSection 14.5.2 MeterAn electronic voltmeter, operating on an inputof less than 9 3 1012A and having a sensitivity of 62mVover a range of at least 61 V. The m
12、eter shall be electrostati-cally shielded, and the shield shall be connected to the ground.35.3 Cell System, consisting of a reference and indicatingelectrode. The reference electrode should be a sturdy, pencil-type glass electrode, having a shielded lead connected toground. The indicating electrode
13、 shall be made from a silver1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.03 on Elemental Analysis.Current edition approved May 1, 2010. Published May 2010. Originallyapproved in 1973. Last pr
14、evious edition approved in 2004 as D322704A. DOI:10.1520/D3227-04R10.2For 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 Summary page onthe ASTM
15、website.3Any apparatus that will give equal or better precision is acceptable.1Copyright ASTM International. 100 Barr Harbour Dr. PO Box C-700 West Conshohocken, Pennsylvania 19428-2959, United StatesCopyright by ASTM Intl (all rights reserved); Thu Nov 25 20:05:49 EST 2010Downloaded/printed byGuo D
16、ehua (CNIS) pursuant to License Agreement. No further reproductions authorized.wire, 2 mm (0.08 in.) in diameter or larger, mounted in aninsulated support. Silver billet electrodes can also be used.5.4 Buret, 10-mL capacity, graduated in 0.05-mL intervals,with a tip that extends approximately 120 mm
17、 (5 in.) below thestopcock.5.5 Titration Stand, preferably built as an integral part of themeter housing and provided with supports for the electrodesand electrical stirrer, all connected to ground. No permanentchange in meter reading should be noticeable upon connectingor disconnecting the stirring
18、 motor.6. Reagents and Materials6.1 Purity of ReagentsReagent 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 Chemical Society,where such specifications
19、 are available.4Other 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.6.1.1 Commercially available solutions may be used inplace of prepared laboratory solutions, when they are cer
20、tifiedto meet the required concentrations.6.1.2 Alternate volumes of solutions and solvents may beprepared, when an equivalent concentration is maintained.6.2 WaterReagent grade, Type I, Specification D1193.6.3 Cadmium Sulfate, Acid Solution (150 g/L)Dissolve150 g of cadmium sulfate (3CdSO48H2O) in
21、water.(WarningPoison. May be fatal if swallowed or inhaled. Aknown carcinogen (animal positive).) Add 10 mL of diluteH2SO4(WarningPoison. Causes severe burns. Harmful orfatal if swallowed or inhaled) and dilute to 1 L with water.6.4 Potassium Iodide, Standard Solution (approximately 0.1mol/L)Dissolv
22、e 17 g of KI (weigh to 0.01 g) in 100 mL ofwater in a 1-L volumetric flask and dilute to 1 L. Calculate theexact molarity.6.5 Propan-2-ol(WarningFlammable. WarningUnless inhibited against it, peroxides can form in propan-2-olwhen stored in the same container that is exposed to air. Whenthis happens
23、and the propan-2-ol evaporates to dryness, anexplosion can occur. When peroxides are suspected, they maybe removed by percolation through an activated aluminacolumn.)6.6 Silver Nitrate, Standard Alcoholic Solution (0.1 mol/L)Dissolve 17 g of AgNO3in 100 mL of water in a 1-Lvolumetric flask and dilut
24、e to 1 L with propan-2-ol (99 %) (seeNote 1). Store in a dark bottle and standardize at intervalsfrequent enough to detect a change of 0.0005 or greater inmolarity.NOTE 1It is important to pass the propan-2-ol through a column ofactivated alumina to remove peroxides that may have formed on storage;f
25、ailure to remove peroxides will lead to low results. It is not necessary toperform this step if the alcohol is tested and found free of peroxides.6.6.1 StandardizationAdd six drops of concentratedHNO3(relative density 1.42) (WarningPoison. Causes se-vere burns. Harmful or fatal if swallowed or inhal
26、ed) to 100mL of water in an appropriately sized beaker (for example, a200-, 250-, or 300-mL size beaker is typically large enough).Remove oxides of nitrogen by boiling for 5 min. Cool toambient temperature. Pipet 5 mL of 0.1 mol/L KI solution intothe beaker and titrate with the AgNO3solution choosin
27、g theend point at the inflection of the titration curve.6.7 Silver Nitrate, Standard Alcoholic Solution (0.010 mol/L)Prepare daily when the test is being performed by dilutionof the 0.1 N standard. Pipet 100 mL of the 0.1 mol/L standardinto a 1-L volumetric flask and dilute to volume with propan-2-o
28、l. Calculate the exact molarity.6.8 Sodium Sulfide Solution (10 g/L)Dissolve 10 g ofNa2S in water and dilute to 1 L with water. Prepare fresh asneeded.6.9 Sulfuric Acid, dilute. Cautiously dilute five volumes ofwater with one volume of sulfuric acid (relative density 1.84).(WarningAdding the acid wi
29、ll generate heat: mix well. Ifwater begins to boil, cool before adding more acid.) Note thatonly limited volumes are required because only 10 mL areneeded for each litre of cadmium sulfate solution.6.10 Titration SolventLow molecular weight mercaptans,as usually found in gasoline, are readily lost f
30、rom the titrationsolution if an acidic titration solvent is used. For the determi-nation of the higher molecular weight mercaptan as normallyencountered in kerosines, aviation turbine fuels, and distillatefuels, the acidic titration solvent is used to achieve more rapidequilibrium between successive
31、 additions of the titrant.6.10.1 Alkaline Titration SolventDissolve 2.7 g of sodiumacetate trihydrate (NaC2H3O23H2O) or 1.6 g of anhydroussodium acetate (NaC2H3O2) in 25 mL of water free ofdissolved oxygen and pour into 975 mL of propan-2-ol (99 %)(Note 1). When necessary, remove dissolved oxygen by
32、 purg-ing the solution with a rapid stream of nitrogen for 10 min eachday prior to use; keep protected from the atmosphere. Tominimize oxygen from dissolving in the solution duringstorage, an option exists to nitrogen blanket the solution priorto sealing the solvent container.6.10.2 Acidic Titration
33、 SolventDissolve 2.7 g ofNaC2H3O23H2Oor1.6gofNaC2H3O2in 20 mLof water freeof dissolved oxygen and pour into 975 mL of propan-2-ol(99 %) (Note 1) and add 4.6 mL of glacial acetic acid. Whennecessary, remove dissolved oxygen by purging the solutionwith a rapid stream of nitrogen for 10 min each day pr
34、ior touse; keep protected from the atmosphere. To minimize oxygenfrom dissolving in the solution during storage, an option existsto nitrogen blanket the solution prior to sealing the solventcontainer.6.11 Polishing Paper or Cloth, 620 m average particlesize abrasive.7. Sampling7.1 Take the sample in
35、 accordance with Practice D4057 orPractice D4177.4Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For Suggestions on the testing of reagents notlisted by the American Chemical Society, see Annual Standards for LaboratoryChemicals, BDH Ltd., Pool
36、e, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.D3227 04a (2010)2Copyright by ASTM Intl (all rights reserved); Thu Nov 25 20:05:49 EST 2010Downloaded/printed byGuo Dehua (CNIS) pursuant to License Agreement. No furth
37、er reproductions authorized.7.2 Methanethiol (methyl mercaptan) has a boiling point of6.2C and may be expected to be present in light untreatedgasolines. Therefore, when the presence of this low boilingthiol (mercaptan) is known or expected, specimen to be testedshall be kept below 4C to prevent the
38、 loss of mercaptan fromsuch samples.8. Preparation of Apparatus8.1 Glass ElectrodeAfter each manual titration, or batchof titrations, in the case of automatic titration systems, wipe theelectrode with a soft, clean tissue and rinse with water. Cleanthe electrode at frequent intervals (at least once
39、a week) bystirring in cold chromic acid solution (WarningCausessevere burns. A recognized carcinogen. Strong oxidizercontact with other material may cause fire. Hygroscopic. Anequivalent, chromium-free cleaning solution may be used) fora few seconds (10 s maximum). When not in use, keep lowerhalf of
40、 the electrode immersed in water.8.2 Silver/Silver-Sulfide ElectrodeEach day prior to use,or as triggered by the analysis of a quality control (QC) sample(see Section 12), prepare a fresh silver sulfide coating on theelectrode by the following method:8.2.1 Burnish electrode with polishing paper or c
41、loth until aclean, polished silver surface shows.8.2.2 Place electrode in operating position and immerse it in100 mL of titration solvent containing 8 mL of Na2S solution.8.2.3 Add slowly from a buret, with stirring, 10 mL of 0.1mol/L AgNO3solution over a period from 10 to 15 min.8.2.4 Remove electr
42、ode from solution, wash with water, andwipe with a soft, clean tissue.8.2.5 Between manual titrations, or batches of titrations inthe case of automatic titration systems, store the electrode aminimum of 5 min in 100 mLof titration solvent containing 0.5mL of the 0.1 mol/L AgNO3solution.9. Procedure9
43、.1 Determination of DensityIf the sample is to be mea-sured volumetrically, determine the density by Test MethodD1298 or Test Method D4052 at the temperature at which thetest portion will be taken, either directly or from the densitydetermined at a reference temperature and converted to thetransfer
44、temperature by use of the Petroleum MeasurementTables (Guide D1250).9.2 Removal of Hydrogen SulfideTest the sample qualita-tively for hydrogen sulfide (H2S) by mixing 5 mLof the samplewith 5 mL of the acid CdSO4solution. If no precipitateappears, proceed with the analysis of the sample as describedi
45、n 9.3. If a yellow precipitate appears, remove the H2Sinthefollowing manner: Place a quantity of the sample, three to fourtimes that required for the analysis, in a separatory funnelcontaining a volume of the acid CdSO4solution equal to onehalf that of the sample and shake vigorously. Draw off anddi
46、scard the aqueous phase containing the yellow precipitate.Repeat the extraction with another portion of the CdSO4solution. Again draw off the aqueous phase, and wash thesample with three 25 to 30-mL portions of water, withdrawingthe water after each washing. Filter the hydrocarbon through arapid pap
47、er. Test a small portion of the washed sample, such asin a test tube or vial, with a few millilitres of the CdSO4solution as described previously. If no further precipitate isformed, proceed as directed in 9.3. If a precipitate appears,repeat the extraction with the CdSO4solution until all of theH2S
48、 has been removed. (WarningCertain straight run gaso-lines can contain significant amounts of both low molecularweight mercaptans and dissolved elemental sulfur, which,when heated under total reflux conditions, may produce H2Sbythe inter-reaction of both. This phenomenon is particularlynoticed in st
49、raight run gasolines produced from some naturalgas condensates. Therefore, it is advisable that during theremoval of H2S (and after all H2S has been extracted), that noheat should be applied to the sample.)9.2.1 When the test results obtained are not for refereepurposes and Quality Assurance/Quality Control (QA/QC)protocol permits, an alternative test for, and a procedure for theremoval of, hydrogen sulfide can be used. This process useslead acetate paper and sodium hydrogen carbonate and isdescribed in Appendix X1.9.2.2 There are available automa
