1、Designation: D1533 00 (Reapproved 2005) D1533 12Standard Test Method forWater in Insulating Liquids by Coulometric Karl FischerTitration1This standard is issued under the fixed designation D1533; 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 () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1. Scope1.1 This test me
3、thod covers the measurement of water present in insulating liquids by coulometric Karl Fischer titration. Thistest method is used commonly for test specimens below 100 % relative saturation of water in oil. The coulometric test method isknown for its high degree of sensitivity (typically 10 g H2O).
4、This test method requires the use of equipment specifically designedfor coulometric titration.1.2 This test method recommends the use of commercially available coulometric Karl Fischer titrators and reagents.1.3 The values stated in SI units are to be regarded as standard. No other units of measurem
5、ent are included in this standard.1.4 This standard does not 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 practice and determine the applicability of regulatorylimitatio
6、ns prior to use. For specific precautionary statements see 8.1 and A2.1.2. Referenced Documents2.1 ASTM Standards:2D923 Practices for Sampling Electrical Insulating LiquidsD3613 Practice for Sampling Insulating Liquids for Gas Analysis and Determination of Water Content (Withdrawn 2007)32.2 IEC Stan
7、dard:IEC 60814: Insulating LiquidsOil-Impregnated Paper and PressboardDetermination of Water by Automatic CoulometricKarl Fischer Titration33. Summary of Test Method3.1 This test method is based on the reduction of iodine containing reagent according to the traditional Karl Fischer reaction.The prop
8、osed reaction mechanism is as follows:4SO2 1CH3OH1RN5RNH#SO3CH3 (1)H2O1I2 1RNH#SO3CH3 12RN5RNH#SO4CH3 12RNH#IRN5Base!The endpoint is determined amperometrically with a platinum electrode that senses a sharp change in cell resistance when theiodine has reacted with all of the water in the test specim
9、en.3.2 The coulometric Karl Fischer test method requires the use of an automatic titrator with commercially available reagents.Karl Fischer instruments regenerate iodine coulometrically from the iodide in the Karl Fischer reagent. The test specimen isinjected into a titration cell where the iodine c
10、onsumed by the reaction with water is electrolytically regenerated by anodic1 This test method is under the jurisdiction of ASTM Committee D27 on Electrical Insulating Liquids and Gasesand is the direct responsibility of Subcommittee D27.06on Chemical Test.Current edition approved Oct. 1, 2005Dec. 1
11、, 2012. Published November 2005December 2012. Originally approved in 1958. Last previous edition approved in 20002005as D1533 00.D1533 00(2005). DOI: 10.1520/D1533-00R05.10.1520/D1533-12.2 For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at servic
12、eastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 American National Standards Institute, 11 West 42nd Street, New York, NY 100368002.4 Scholz, E., “Karl-Fischer Titration,” Springer-Verlag, Berlin, Heidelberg, New York,
13、 Tokyo, 1984, 140 pp.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 may not be technically possible to adequately depict all changes accurately, ASTM recommends that us
14、ers 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.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1oxidation of iodide. The co
15、mpletion of the reaction is detected with a platinum sensing electrode. The coulombs of electricityrequired to generate the necessary amount of iodine then is converted into the amount of water present in the test specimen by useof the Faraday equation.3.3 Titration CellThe coulometric titration cel
16、l consists of either a sealed vessel containing both an anode and cathode whichare separated by a diaphragm or a sealed vessel containing an anode and cathode which are not separated by a diaphragm. In bothcells the anode compartment contains a solution consisting of sulfur dioxide, iodide, and an a
17、mine in a solvent containingmethanol/chloroform or methanol/longer chain alcohol. In the cell with a diaphragm the cathode compartment contains similarreagents optimized for cathodic reduction.4. Significance and Use4.1 Electrical characteristics of an insulating liquid may be affected deleteriously
18、 by excessive water content. A high watercontent may make a dielectric liquid unsuitable for some electrical applications due to deterioration of properties such as thedielectric breakdown voltage.4.2 These tests are suitable for use in acceptance specifications, in control of processing, and in eva
19、luating the condition ofdielectric liquids in service.5. Interferences5.1 Compounds such as aldehydes, ketones, free halogens, most acids, and oxidizing or reducing agents may interfere withcoulometric Karl Fischer titrators. If a drifting end point is noted, an alternative solvent system or another
20、 titration method iswarranted. If this drifting end point cannot be corrected, the water values should be regarded as suspect. A detailed discussion ofinterfering substances can be found in the treatise on aquametry.55.2 Studies have shown that the water content of an insulating liquid sample may be
21、 influenced significantly by the samplecontainer.6 A sample may either gain or lose water on storage in a glass container depending upon the initial water content of thesample, the manner in which the container is cleaned and dried, and the length of storage time before analysis. In addition, sample
22、bottles should not be dried at temperature in excess of 110C and should be rinsed with the liquid being tested prior to taking thetest specimen.5.3 Erroneous low readings may be obtained if previous spent oil test specimens are not removed from the solvent system ona routine basis. Excess oil may no
23、t mix thoroughly with the solvent system thus preventing the total water content of that testspecimen from being measured properly. Stirring should be at such a rate that an oil layer will not form on top of the reagent. Ifsuch an oil layer does form while at the instruments maximum stirrer speed, s
24、top testing and remove the oil layer. If accurate resultscan not be obtained, the solution should be discarded.5.4 Upon setting up of the titration vessel and solvent system, the walls of the titration vessel should be wetted by swirling thesolvent system solution around in the vessel.6. Apparatus6.
25、1 Coulometric Titrator, consisting of a detector electrode, generator electrode, titration vessel, magnetic stirrer, and controlunit.6.1.1 Detector ElectrodesThis electrode pair amperometrically determines the end point of titration by measuring a sharpchange in cell resistance.6.1.2 Generator Elect
26、rodesThis electrode pair performs the cathodic reduction of iodide, which allows the Karl Fischerreaction to take place. It may consist of two platinum meshes or wires separated by a diaphragm within a glass assembly or twoplatinum meshes or wires not separated by a diaphragm.6.2 Titration FlaskThe
27、titration flask will be of suitable capacity and will be protected against atmospheric moisture. A bottomdrain cock is desirable but not necessary for removing reagents.6.3 StirrersMeans for agitation during titration will consist of a magnetic stirrer with a glass or TFE-fluorocarbon-coveredstirrin
28、g bar about 2 to 5 cm long or appropriate to the titration vessel. The bar should be cleaned thoroughly, rinsed with methanol,dried in an oven for 1 h at 100C, and stored in a desiccator until used. In a sealed system, recleaning and redrying are not necessaryfor routine use.6.4 Transfer SyringesSyr
29、inges shall be used of a suitable size to accommodate instrument manufacturers recommendationof sample size. Syringes may be glass or plastic. Glass syringes shall be cleaned and dried for 1 h at 100C prior to use. Plasticsyringes shall be disposed of following each sample use.5 Mitchell, J., Jr. an
30、d Smith, D. M., “AquametryA Treatise on Methods for the Determination of Water, Part IIIthe Karl Fischer Reagent,” 2nd ed., J. Wiley and Sons,Inc., New York, NY 1977.6 Gedemer, T., “Determination of Water in Oil by Karl Fischer Method, Part II, Changes in Moisture Content During Storage,” American L
31、aboratory 7 (10), pp. 4350(1975).D1533 1226.5 NeedlesNeedles that are to be fitted to the transfer syringes shall be long enough to inject samples directly below thesurface of the Karl Fischer reagent. They should be of a large enough gauge to allow for easy transfer of the sample.6.6 Septums, used
32、to seal sample port, allowing the introduction of test specimens with a minimum amount of contaminationfrom atmospheric moisture.6.7 Sealing GreaseIf the apparatus does not have a gasket seal, use a sealing grease to seal the titration chamber againstatmospheric moisture.6.8 Drying Oven, vacuum or a
33、ir circulating.6.9 Desiccator, standard laboratory type with color change indicator.6.10 Analytical Balance, capable of weighing to 6 0.001 g.7. Reagents7.1 Purity of ReagentsUnless otherwise indicated, all reagents shall conform to the specifications of the Committee onAnalytical Reagents of the Am
34、erican Chemical Society, where such specifications are available.77.2 Coulometric Karl Fischer Reagent, can be obtained commercially. Refer to Annex A1 for information on alternative solventsystems.7.2.1 Anode Reagent, frequently referred to as vessel solution.7.2.2 Cathode Reagent, frequently refer
35、red to as generator solution.7.3 Verification SolutionsVerification solutions are available commercially.8 Verification solutions may be formulatedin-house from long chain alcohols.7.3.1 The moisture content of water-saturated octanol is:Water-saturated 1-Octanol 39.2 0.85 mg/mL of solution97.3.2 Th
36、e water-saturated alcohol can be prepared by adding deionized water to the alcohol (ACS reagent grade) at 25C suchthat the final mixture consists of a two-phase system in which the lower water phase is at least 2 cm high. Initially, this solutionshould be mixed thoroughly and allowed to stand at roo
37、m temperature for at least three days to achieve complete equilibration.NOTE 1For the best accuracy the solution should not be mixed or shaken after standing. Remove the sample aliquot from the top phase and injectit immediately into the titration cell. The degree of saturation of the water-saturate
38、d 1-Octanol varies 1 % between 10 and 30C.7.3.3 The response of the instrument shall be verified with 1 to 2 L of water; this can give a response value of 1000 to 2000g within the specified precision of the instrument.8. Safety Precautions8.1 Pyridine was the organic amine that was traditionally use
39、d in Karl Fischer reagents; however, pyridine-free formulations arenow available commercially. Pyridine-free reagents titrate faster and are less toxic, less odorous, and more stable than pyridinetypes. The reagents may contain potentially hazardous chemicals, such as iodine, pyridine, sulfur dioxid
40、e, methanol, chloroform,chlorinated hydrocarbons, or other organic materials. Wear chemical resistant gloves when mixing the reagents and removingsolution from the titration chamber. Care must be exercised to avoid unnecessary inhalation of reagent vapors or direct contact ofthe reagents with the sk
41、in or eyes. Following accidental spillage, flush the affected area with copious amounts of water.NOTE 2Carefully read and follow manufacturers instructions and Material Safety Data Sheet when using commercially available reagent systems.9. Sampling9.1 The preferred method for sampling insulating liq
42、uids is Practice D3613; however, Practices D923 also are suitable. . If thetest specimen is cloudy or contains free water, it may be difficult to obtain a representative specimen.10. Preparation of Apparatus10.1 Thoroughly clean and dry the titration vessel and then reassemble according to the manuf
43、acturers recommendations.Follow the instructions provided in Annex A2 for detailed instructions on cleaning.10.2 Fill reagent reservoirs with appropriate reagents according to the manufacturers instructions.10.3 Turn the instrument on and allow to stabilize.7 Reagent Chemicals, American Chemical Soc
44、iety 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 Pharmacopeia and NationalFormulary, U.S. Pharmaco
45、peial Convention, Inc. (USPC), Rockville, MD.8 The sole source of supply of verification solutions, RM 8506 and RM 8507, known to the committee at this time is the National Institute of Standards and Technology(NIST), Gaithersburg, MD 20899. If you are aware of alternative suppliers, please provide
46、this information to ASTM International Headquarters. Your comments will receivecareful consideration at a meeting of the responsible technical committee,1 which you may attend.9 SRM 2890 Water Saturated 1-Octanol Certificate of Analysis, NIST, Gaithersburg, MD, 25 August 1998.D1533 12311. Verificati
47、on of System Operation11.1 The accuracy of titration of the instrument and reagents shall be verified prior to beginning of testing by use of a suitableverification solution (see 7.3) containing a known quantity of moisture. It is desirable to verify the system operation using asolution that approxi
48、mates the same range of water expected to be in the samples. Verification solutions shall be run with newreagents prior to testing. If verification solution results lie outside parameters established by the manufacturer for acceptablemoisture content of the solution, reagents shall be changed and re
49、verified.12. Procedure12.1 After verifying the system is operating properly, allow the instrument to restabilize prior to use.12.2 Follow the manufacturers instructions for suggested specimen size for an expected range of moisture content.12.3 Using an appropriate syringe and needle (see 6.4 and 6.5) sample the insulating fluid to be tested. Prior to sampling, rinsethe syringe and needle with the liquid to be tested one time.12.4 Determine the sample mass by difference to three significant figures by weighing the test specimen before and af
