1、Designation: D 6470 99 (Reapproved 2004)An American National StandardStandard Test Method forSalt in Crude Oils (Potentiometric Method)1This standard is issued under the fixed designation D 6470; the number immediately following the designation indicates the year oforiginal adoption or, in the case
2、of revision, the year 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. Scope1.1 This test method covers the determination of salt incrude oils. For the purpose of this test
3、 method, salt is expressedas % (m/m) NaCl (sodium chloride) and covers the range from0.0005 to 0.15 % (m/m).1.2 The limit of detection is 0.0002 % (m/m) for salt (asNaCl).1.3 The test method is applicable to nearly all of the heavierpetroleum products, such as crude oils, residues, and fuel oils.It
4、may also be applied to used turbine oil and marine diesel fuelto estimate seawater contamination. Water extractable salts,originating from additives present in oils, are codetermined.1.4 The values stated in SI units are to be regarded as thestandard.1.5 This standard does not purport to address all
5、 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.2. Referenced Documents2.1 ASTM Standards:2D 329 Specification f
6、or AcetoneD 770 Specification for Isopropyl AlcoholD 843 Specification for Nitration Grade XyleneD 1193 Specification for Reagent WaterD 4006 Test Method for Water in Crude Oil by DistillationD 4057 Practice for Manual Sampling of Petroleum andPetroleum ProductsD 4177 Practice for Automatic Sampling
7、 of Petroleum andPetroleum ProductsD 4377 Test Method for Water in Crude Oils by Potentio-metric Karl Fischer TitrationD 4928 Test Method for Water in Crude Oils by Coulom-etric Karl Fischer TitrationE 200 Practice for Preparation, Standardization, and Stor-age of Standard and Reagent Solutions for
8、ChemicalAnalysis3. Summary of Test Method3.1 After homogenizing the crude oil with a mixer, aweighed aliquot is dissolved in xylene at 65C and extractedwith specified volumes of alcohol, acetone, and water in anelectrically heated extraction apparatus. A portion of theaqueous extract is analyzed for
9、 total halides by potentiometrictitration.4. Significance and Use4.1 A knowledge of water extractable inorganic halides inoil is important when deciding whether or not the oils needdesalting. Excessive halide, especially in crude oil, frequentlyresults in higher corrosion rates in refining units.5.
10、Apparatus5.1 Extraction Apparatus, made of borosilicate glass, con-forming to the dimensions given in Fig. 1, and consisting of thefollowing component parts:5.1.1 Boiling Flask, 500 mL capacity.5.1.2 Hopkins Reflux Condenser, having a vapor outletconnected by a rubber tube to an outside vent or to a
11、 suctionhood.5.1.3 Thistle Tube, approximately 70 mL capacity, with aline to indicate approximately the 50 mL level.5.1.4 Heating Tube, containing a chimney for increasingconvection in the liquid.5.1.5 Heating Coil, 250 W, consisting of a suitable gage ofNichrome wire.5.1.6 Rheostat, of suitable res
12、istance and capacity, forregulating the heater.5.2 Safety Shield, colorless safety glass, or equivalent, to bemounted in front of the extraction apparatus (see 5.1).5.3 Sampling Tube, glass, length approximately 600 mm,I.D. approximately 5 mm, with a bulb having a volume of 100mL, or more, and drawn
13、 out at one end to an opening of insidediameter (I.D.) 2 to 3 mm. A pipette with cut-off tip makes asuitable sample tube.1This 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.
14、Current edition approved May 1, 2004. Published June 2004. Originallyapproved in 1999. Last previous edition approved in 1999 as D 647099.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume
15、information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.4 Potentiometric Titration Equipment, with a measuringaccuracy of 6 2 mV, or better, provided with a silve
16、r indicatingand a glass reference electrode and 10 mL burette, preferablypiston type. If an automatic titrator is used, this shall be capableof adding fixed increments of titrant (see 9.3.3.2).5.5 Magnetic Stirrer, with polytetrafluoroethylene (PTFE)-coated stirring bar.5.6 Homogenizer. A mixer with
17、 counter-rotating bladesoperating at approximately 3000 r/min (50/s) is usually suitablefor homogenization of samples up to 500 mL. Other designscan also be used provided the performance conforms to therequirements described in Annex A1.5.7 Oven, explosion-proof, temperature 65 6 5C.5.8 Filter Paper
18、, Whatman No. 41, or equivalent.5.9 Stopwatch.6. Reagents and Materials6.1 Purity of ReagentsUnless otherwise indicated, it isintended that all reagents shall conform to the specifications ofthe Committee onAnalytical Reagents of theAmerican Chemi-cal Society where such specifications are available.
19、36.2 Purity of WaterFor all purposes where water ismentioned, reagent water of a suitable purity shall be used.Various types of reagent water are described in SpecificationD 1193.6.3 Acetone (2-propanone), conforming to SpecificationD 329. (WarningExtremely flammable. Vapors may causeflashfire.)6.4
20、Alcohol, for example, 95 % (V/V) ethanol, or propan-2ol (isopropyl alcohol), conforming to Specification D 770.(WarningFlammable.)3Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the Americ
21、an Chemical Society, see Annual Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.NOTE 1Hopkins-type condenser is used.FIG. 1 Extraction ApparatusD 6470 99 (2004)26.5 Ba
22、rium Nitrate, A.R., crystals. (WarningBariumcompounds and their solutions present a health risk if incor-rectly handled. Prevent all contact.)6.6 Hydrochloric Acid, 0.1 mol/L, aqueous. Add 9 mL ofA.R. concentrated hydrochloric acid (density 1.19 g/mL) to 1 Lwith water. (WarningCorrosive. Causes skin
23、 burns.)6.7 Nitric Acid, 5 mol/L, aqueous. Cautiously add 325 mLof A.R. concentrated nitric acid (density 1.42 g/mL) to 1 Lwater, while stirring. (WarningCorrosive. Causes skinburns.)6.8 Silver Nitrate Solution, standard, c(AgNO3) = 0.1mol/L, aqueous. Prepare, standardize and store as described inPr
24、actice E 200 for 0.1 N aqueous solution, reading concentra-tions in mol/L in place of normality. Restandardize regularly,but in any case before preparation of the standard 0.01 mol/Lsolution (see 6.9)NOTE 1Alternatively, ampoules containing concentrated solutions forpreparation of standard volumetri
25、c solutions are available from varioussuppliers. (WarningSilver compounds and their solutions present ahealth risk if incorrectly handled. Prevent all contact.)6.9 Silver Nitrate Solution, standard, c(AgNO3) = 0.01mol/L, aqueous. Prepare shortly before use by accuratelydiluting one volume of the rec
26、ently restandardized 0.1 mol/Lsilver nitrate solution (Warningsee 6.8) to a tenfold volumewith water.6.10 Sodium Chloride Solution, approximately 1 mmol/L,aqueous. Dissolve 59 6 1 mg sodium chloride in 1 L water.6.11 Xylene, conforming to Specification D 843.(WarningXylene presents a health risk if
27、incorrectlyhandled. Avoid inhalation. Extract vapor by working in a fumecupboard.)6.12 Lead Acetate Paper.6.13 Polishing Paper, 800 grit, or finer, to polish the silverelectrode.7. Sampling and Sample Preparation7.1 Sampling is defined as all the steps required to obtain analiquot representative of
28、the contents of any pipe, tank, or othersystem, and to place the sample into the laboratory samplecontainer. The laboratory sample container and sample volumeshall be of sufficient dimensions and volume to allow mixing,as described in 7.4. (WarningThe results of the round robinhave shown that for re
29、liable results, strict adherence to thesampling and mixing procedure is of the utmost importance.)7.2 Laboratory SampleThe sample of crude oil presentedto the laboratory or test facility for analysis by this test method.Only representative samples obtained as specified in PracticesD 4057 and D 4177
30、shall be used for this test method.7.3 Test SampleThe sample aliquot obtained from thelaboratory sample for analysis by this test method. Oncedrawn, the entire portion of the test sample will be used in theanalysis. Mix the laboratory sample properly, as described in7.4, prior to drawing the test sa
31、mple.7.4 Homogenize the laboratory sample of crude oil imme-diately (within 15 min) before drawing the test sample toensure complete homogeneity. Mix the sample at room tem-perature (15 to 25C), or less, in the laboratory samplecontainer, and record the temperature of the sample in degreesCelsius im
32、mediately before mixing. Heat waxy samples, solidat room temperature, to 3C above their pour point in order tofacilitate test sample withdrawal. Select the type of mixerrelated to the quantity of crude oil in the laboratory samplecontainer. Before any unknown mixer is used, the specifica-tions for t
33、he homogenization test (see Annex A1) shall be met.Reevaluate the mixer for any changes in the type of crude, thequantity of crude, the shape of the sample container, or themixing conditions (such as mixing speed and time of mixing).7.5 For small laboratory sample containers and volumes, 50to 500 mL
34、, a nonaerating, high speed (3000 r/min), shear mixeris required. Use the mixing time, mixing speed, and heightabove the bottom of the container found to be satisfactory toAnnex A1. For larger containers and volumes, appropriatemixing conditions shall be defined by following a set ofprocedures simil
35、ar to those outlined in Annex A1 and PracticeD 4177 but modified for application to the larger containersand volumes. Clean and dry the mixer between samples.7.6 Record the temperature of the sample immediately afterhomogenization. The rise in temperature between this readingand the initial reading
36、prior to mixing (see 7.4) shall not exceed10C, otherwise excessive loss of volatile vapors can occur orthe dispersion can become unstable.7.7 In order to ensure that crude oils with rapidly settlingimpurities are properly sampled, withdraw the test samplecontainer immediately after homogenization by
37、 lowering thetip of the sample tube (see 5.3) almost to the bottom of thecontainer, and withdrawing the test sample as quickly aspossible. Clean and dry the sample tube before and aftersampling.8. Preparation of Apparatus8.1 Extraction ApparatusTo reduce the risk of superheat-ing and the resulting h
38、azards, introduce a gentle stream of airinto the bottom of the extraction apparatus. This can be done bypassing a length of hypodermic tubing through the bore of thetap so that the lower end reaches the bottom of the heatingtube, while the upper end of the tubing is passed through arubber bung in th
39、e top of the thistle tube. Place the extractionapparatus behind a safety screen. Shield all electrical resis-tances and devices; alternatively, remove them from theimmediate vicinity of the extraction apparatus.8.2 Potentiometric Titration Equipment:8.2.1 Glass ElectrodeBefore each titration (or eac
40、h seriesof titrations), rinse the electrode with water and soak it for atleast 10 min in 0.1 mol/L hydrochloric acid (see 6.6). Thenrinse again with water. After titrations store the electrodeimmersed in reagent water.8.2.2 Silver ElectrodePolish the silver electrode beforeeach set of titrations wit
41、h polishing paper (see 6.13) until aclean, polished metal surface is obtained.9. Procedure9.1 Extraction:9.1.1 Weigh about 40 g of sample, to the nearest 0.1 g, intoa 250 mL beaker and heat on a water bath or in an oven to 656 5C. Heat 40 6 1 mL of xylene to the same temperature andadd slowly to the
42、 sample while stirring constantly untildissolution is complete. Transfer the solution quantitatively toD 6470 99 (2004)3the extraction apparatus, rinsing the beaker with two separateportions of 15 6 1 mL of hot xylene and adding these rinsingsalso to the extraction apparatus.9.1.2 While the solution
43、 is still hot, add 25 6 1mLofethanol or isopropyl alcohol and 15 6 1 mL of acetone, usingthese portions for further rinsing of the beaker. Switch on theheating element of the extraction apparatus to full heat untilboiling begins, then adjust the rheostat to regulate the heat tomaintain boiling at a
44、vigorous rate, but not at such a rate tocause bumping in the flask or to cause the condenser to flood.Allow to reflux for 2 min after the liquid starts boiling (see8.1). Switch off the heater. When boiling ceases, add 125 6 1mL of water and again bring the liquid to the boil and reflux fora further
45、15 min.9.1.3 Switch off the heater, and allow the two phases toseparate for 5 to 10 min. Draw off the aqueous phase, filteringthrough a filter paper into a conical flask of suitable capacity,stopper the flask, and retain the contents for the total halidedetermination as described in 9.2 and 9.3.9.2
46、Removal of Sulfur-Containing CompoundsPipet 50.0mL of the aqueous extract (see 9.1.3) into a beaker, and add 5mL of 5 mol/L nitric acid (see 6.7). Cover the beaker with awatch-glass, and bring the contents to the boil. Test the vaporsperiodically for hydrogen sulfide with lead acetate paper andconti
47、nue boiling for a further 5 min after a negative result hasbeen obtained. Allow the contents of the beaker to cool andquantitatively transfer to a 250-mL titration vessel, rinsing thebeaker with water. (WarningHydrogen sulfide presents ahealth risk if incorrectly handled. Avoid inhalation. Extractes
48、caping gas by working in a fume cupboard.)9.3 Salt Determination:9.3.1 Pipet 10.0 mL of the 1 mmol/L sodium chloridesolution (see 6.10; see Note 2) in the titration vessel (see 9.2).Adjust the volume of the sample solution in the vessel to 150mL with acetone (see Note 3). Add approximately 0.5 g ofb
49、arium nitrate crystals. Stir to dissolve the barium nitrate.NOTE 2To obtain a titration end point even for small amounts ofchloride, a fixed amount of sodium chloride is added to the blank andsample solution.NOTE 3Acetone is added to lower the solubility of the silver chlorideprecipitate.9.3.2 Fill the burette with 0.01 mol/L silver nitrate solution,place the beaker on a magnetic stirrer, and immerse theelectrodes in the sample solution. Immerse the tip of the buretteapproximately 25 mm below the liquid surface, and adjust themagnetic stirrer to produce
