1、Designation: D6304 16Standard Test Method forDetermination of Water in Petroleum Products, LubricatingOils, and Additives by Coulometric Karl Fischer Titration1This standard is issued under the fixed designation D6304; the number immediately following the designation indicates the year oforiginal ad
2、option 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 agencies of the U.S. Department of Defe
3、nse.1. Scope1.1 This test method covers the direct determination ofwater in the range of 10 mgkg to 25 000 mgkg entrainedwater in petroleum products and hydrocarbons using auto-mated instrumentation. This test method also covers theindirect analysis of water thermally removed from samples andswept w
4、ith dry inert gas into the Karl Fischer titration cell.Mercaptan, sulfide (Sor H2S), sulfur, and other compoundsare known to interfere with this test method (see Section 5).1.2 This test method is intended for use with commerciallyavailable coulometric Karl Fischer reagents and for the deter-minatio
5、n of water in additives, lube oils, base oils, automatictransmission fluids, hydrocarbon solvents, and other petroleumproducts. By proper choice of the sample size, this test methodmay be used for the determination of water from mg/kg topercent level concentrations.1.3 The values stated in SI units
6、are to be regarded asstandard. No other units of measurement are included in thisstandard.1.4 This standard does 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 practic
7、es and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D1193 Specification for Reagent WaterD1298 Test Method for Density, Relative Density, or APIGravity of Crude Petroleum and Liquid Petroleum Prod-ucts by Hydrometer MethodD4052 Test M
8、ethod 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 ProductsD5854 Practice for Mixing and Handling of Liquid Samplesof Petroleum and
9、 Petroleum ProductsE203 Test Method for Water Using Volumetric Karl FischerTitration3. Summary of Test Method3.1 An aliquot is injected into the titration vessel of acoulometric Karl Fischer apparatus in which iodine for the KarlFisher reaction is generated coulometrically at the anode.When all of t
10、he water has been titrated, excess iodine isdetected by an electrometric end point detector and the titrationis terminated. Based on the stoichiometry of the reaction, 1 molof iodine reacts with 1 mol of water; thus, the quantity of wateris proportional to the total integrated current according toFa
11、radays Law.3.2 The sample injection can be done either by mass orvolume.3.3 The viscous samples can be analyzed by using a watervaporizer accessory that heats the sample in the evaporationchamber, and the vaporized water is carried into the KarlFischer titration cell by a dry inert carrier gas.4. Si
12、gnificance and Use4.1 A knowledge of the water content of lubricating oils,additives, and similar products is important in themanufacturing, purchase, sale, or transfer of such petroleumproducts to help in predicting their quality and performancecharacteristics.4.2 For lubricating oils, the presence
13、 of moisture could leadto premature corrosion and wear, an increase in the debris loadresulting in diminished lubrication and premature plugging offilters, an impedance in the effect of additives, and undesirablesupport of deleterious bacterial growth.1This test method is under the jurisdiction of A
14、STM Committee D02 onPetroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility ofSubcommittee D02.06 on Analysis of Liquid Fuels and Lubricants.Current edition approved July 1, 2016. Published July 2016. Originally approvedin 1998. Last previous edition approved in 2007 as D63
15、04 07, which waswithdrawn in April 2016 and reinstated in July 2016. DOI: 10.1520/D6304-16.2For 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 Su
16、mmary page onthe ASTM website.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States15. Interferences5.1 A number of substances and classes of compoundsassociated with condensa
17、tion or oxidation-reduction reactionsinterferes in the determination of water by Karl Fischertitration. In petroleum products, the most common interfer-ences are mercaptans and sulfides. At levels of less than500 mgkg as sulfur, the interference from these compounds isinsignificant for water concent
18、rations greater than 0.02 % bymass. For more information on substances that interfere in thedetermination of water by the Karl Fischer titration method,see Test Method E203. Some interferences, such as ketones,may be overcome if the appropriate reagents are used.5.2 The significance of the mercaptan
19、 and sulfide interfer-ence on the Karl Fischer titration for water in the 10 mgkg to200 mgkg range has not been determined experimentally. Atthese low water concentrations, however, the interference maybe expected to be significant for mercaptan and sulfide con-centrations of greater than 500 mgkg a
20、s sulfur.5.3 Helpful hints in obtaining reliable results are given inAppendix X1.6. Apparatus6.1 Coulometric Karl Fischer Apparatus (using electromet-ric end point)A number of automatic coulometric KarlFischer titration assemblies consisting of titration cell, plati-num electrodes, magnetic stirrer,
21、 and a control unit are avail-able on the market. Instructions for operation of these devicesare provided by the manufacturers and are not describedherein.6.1.1 Water Vaporizer AccessoryA number of automaticwater vaporizer accessories are available on the market.Instructions for the operation of the
22、se devices are provided bythe manufacturers and are not described herein.6.2 SyringesSamples are most easily added to the titrationvessel by means of accurate glass or disposable plastic syringeswith luer fittings and hypodermic needles of suitable length todip below the surface of the anode solutio
23、n in the cell wheninserted through the inlet port septum. The bores of the needlesused shall be kept as small as possible, but large enough toavoid problems arising from back pressure or blocking whilesampling. Suggested syringe sizes are as follows:6.2.1 Ten microlitres, with a needle long enough t
24、o dipbelow the surface of the anode solution in the cell wheninserted through the inlet port septum and graduated forreadings to the nearest 0.1 L or better. This syringe can beused to accurately inject a small quantity of water to checkreagent performance as described in Section 10.6.2.2 As identif
25、ied in Table 1, syringes of the followingcapacities: 250 L accurate to the nearest 10 L; 500 Laccurate to the nearest 10 L; 1 mL accurate to the nearest0.01 mL; 2 mL accurate to the nearest 0.01 mL; and 3 mLaccurate to the nearest 0.01 mL. A quality gas-tight glasssyringe with a TFE-fluorocarbon plu
26、nger and luer fitting isrecommended.7. Reagents and Materials7.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, all reagents shallconform to the specifications of the Committee on AnalyticalReagents of the American Chemical Society3, where suchspecif
27、ications are available. Use other grades, provided thereagent is of sufficiently high purity to permit its use withoutlessening the accuracy of the determination.7.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean reagent water as definedby Type II of Specif
28、ication D1193.7.3 Xylene, Reagent Grade, less than 100 mgkg to200 mgkg water, dried over a molecular sieve (WarningFlammable. Vapor harmful).7.4 Karl Fischer Reagent, standard commercially availablereagents for coulometric Karl Fischer titrations.7.4.1 Anode SolutionMix six parts of commercial KarlF
29、ischer anode solution with four parts of reagent grade xyleneon a volume basis. Newly made Karl Fischer anode solutionshall be used. Other proportions of anode solution and xylenemay be used and determined for a particular reagent, apparatus,and sample tested. Some samples may not require any xylene
30、,whereas others will require the solvent effect of the xylene(WarningFlammable, toxic if inhaled, swallowed, or ab-sorbed through skin).NOTE 1Toluene may be used in place of xylene. However, theprecision data in Section 17 were obtained using xylene.7.4.2 Cathode SolutionUse standard commercially av
31、ail-able cathode Karl Fischer solution. Newly made solution shallbe used (WarningFlammable, may be fatal if inhaled,swallowed, or absorbed through skin. Possible cancer hazard.).7.4.3 If the sample to be analyzed contains ketone, usecommercially available reagents that have been speciallymodified fo
32、r use with ketones.NOTE 2Some laboratories add the ketone suppressing reagent as partof their standard analytical procedure since often the laboratory does notknow whether the sample contains ketone.7.5 Hexane, Reagent Grade, less than 100 mgkg to200 mgkg water (WarningFlammable. Vapor harmful).Drie
33、d over molecular sieve.7.6 White Mineral OilAlso called paraffin oil or mineraloil. Reagent grade.3Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For Suggestions on the testing of reagents notlisted by the American Chemical Society, see Annual
34、Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.TABLE 1 Test Sample Size Based on Expected Water ContentExpected Water Sample Size g WaterConcentration g or mL Titrate
35、d10 mg kg to 100 mg/kg or g/mL 3.0 30 to 30010 mg kg to 500 mg/kg or g/mL 2.0 200 to 10000.02 % to 0.1 % 1.0 200 to 10000.1 % to 0.5 % 0.5 500 to 25000.5 % to 2.5 % 0.25 1250 to 6250D6304 1627.7 Molecular Sieve 58 to 12 mesh.8. Sampling8.1 Sampling is defined as all the steps required to obtain anal
36、iquot representative of the contents of any pipe, tank, or othersystem and to place the sample into a container for analysis bya laboratory or test facility.8.2 Laboratory SampleThe sample of petroleum productpresented to the laboratory or test facility for analysis by thistest method. Only represen
37、tative samples obtained as specifiedin Practices D4057 and D4177 and handled and mixed inaccordance with Practice D5854 shall be used to obtain thelaboratory sample.NOTE 3Examples of laboratory samples include bottles from amanual sampling, receptacles from automatic samplers, and storagecontainers
38、holding a product from a previous analysis.8.3 Test SpecimenThe aliquot obtained from the labora-tory sample for analysis by this test method. Once drawn, usethe entire portion of the test specimen in the analysis.8.4 Select the test specimen size as indicated in Table 1based on the expected water c
39、oncentration.9. Preparation of Apparatus9.1 Follow the manufacturers directions for preparationand operation of the titration apparatus.9.2 Seal all joints and connections to the vessel to preventatmospheric moisture from entering the apparatus.9.3 Add the Karl Fischer anode solution to the anode (o
40、uter)compartment. Add the solution to the level recommended bythe manufacturer.9.4 Add the Karl Fischer cathode solution to the cathode(inner) compartment.Add the solution to a level 2 mm to 3 mmbelow the level of the solution in the anode compartment.9.5 Turn on the apparatus and start the magnetic
41、 stirrer fora smooth stirring action. Allow the residual moisture in thetitration vessel to be titrated until the end point is reached. Donot proceed beyond this stage until the background current (orbackground titration rate) is constant and less than the maxi-mum recommended by the manufacturer of
42、 the instrument.NOTE 4High background current for a prolonged period may be dueto moisture on the inside walls of the titration vessel. Gentle shaking of thevessel (or more rigorous stirring action) will wash the inside withelectrolyte. Keep the titrator on to allow stabilization to a low background
43、current.10. Calibration and Standardization10.1 In principle, standardization is not necessary since thewater titrated is a direct function of the coulombs of electricityconsumed. However, reagent performance deteriorates withuse and shall be regularly monitored by accurately injecting aknown quanti
44、ty of water (see 7.2) that is representative of thetypical range of water concentrations being determined insamples. As an example, one may accurately inject 10 000 gor 10 L of water to check reagent performance. Suggestedintervals are initially with fresh reagent and then after every tendeterminati
45、ons (see 11.3).11. Procedure A (by Mass)11.1 Add newly made solvents to the anode and cathodecompartments of the titration vessel and bring the solvent toend-point conditions as described in Section 9.11.2 Add the petroleum product test specimen to the titra-tion vessel using the following method:11
46、.2.1 Starting with a clean, dry syringe of suitable capacity(see Table 1 and Note 5), withdraw and discard to waste at leastthree portions of the sample. Immediately withdraw a furtherportion of sample, clean the needle with a paper tissue, andweigh the syringe and contents to the nearest 0.1 mg. In
47、sert theneedle through the inlet port septum, start the titration, andwith the tip of the needle just below the liquid surface, injectthe test specimen. Withdraw the syringe, wipe clean with apaper tissue, and reweigh the syringe to the nearest 0.1 mg.After the end point is reached, record the micro
48、grams of watertitrated.NOTE 5If the concentration of water in the sample is completelyunknown, it is advisable to start with a small trial portion of sample toavoid excessive titration time and depletion of the reagents. Furtheradjustment of the aliquot size may then be made as necessary.11.2.2 When
49、 the background current or titration rate returnsto a stable reading at the end of the titration as discussed in 9.5,additional specimens may be added as per 11.2.1.11.3 Replace the solutions when one of the following occursand then repeat the preparation of the apparatus as in Section9.11.3.1 Persistently high and unstable background current.11.3.2 Phase separation in the anode compartment or oilcoating the electrodes.11.3.3 The total oil content added to the titration vesselexceeds one quarter of the volume of solution in the anodecomp
