ASTM_D_1533_-_12.pdf

Designation:D153312Standard 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 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.1.Scope1.1 This test method covers the measurement of waterpresent in insulating liquids by coulometric Karl Fischertitration.This test method is used commonly for test specimensbelow 100%relative saturation of water in oil.The coulomet-ric test method is known for its high degree of sensitivity(typically 10 g H2O).This test method requires the use ofequipment specifically designed for coulometric titration.1.2 This test method recommends the use of commerciallyavailable coulometric Karl Fischer titrators and reagents.1.3 The values stated in SI units 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 practice and determine the applica-bility of regulatory limitations prior to use.For specificprecautionary statements see 8.1 and A2.1.2.Referenced Documents2.1 ASTM Standards:2D923 Practices for Sampling Electrical Insulating Liquids2.2 IEC Standard:IEC 60814:Insulating LiquidsOil-Impregnated Paper andPressboardDetermination of Water by Automatic Cou-lometric Karl Fischer Titration33.Summary of Test Method3.1 This test method is based on the reduction of iodinecontaining reagent according to the traditional Karl Fischerreaction.The proposed reaction mechanism is as follows:4SO21CH3OH1RN5RNH#SO3CH3(1)H2O1I21RNH#SO3CH312RN5RNH#SO4CH312RNH#IRN5 Base!The endpoint is determined amperometrically with a plati-num electrode that senses a sharp change in cell resistancewhen the iodine has reacted with all of the water in the testspecimen.3.2 The coulometric Karl Fischer test method requires theuse of an automatic titrator with commercially availablereagents.Karl Fischer instruments regenerate iodine coulo-metrically from the iodide in the Karl Fischer reagent.The testspecimen is injected into a titration cell where the iodineconsumed by the reaction with water is electrolytically regen-erated by anodic oxidation of iodide.The completion of thereaction is detected with a platinum sensing electrode.Thecoulombs of electricity required to generate the necessaryamount of iodine then is converted into the amount of waterpresent in the test specimen by use of the Faraday equation.3.3 Titration CellThe coulometric titration cell consists ofeither a sealed vessel containing both an anode and cathodewhich are separated by a diaphragm or a sealed vesselcontaining an anode and cathode which are not separated by adiaphragm.In both cells the anode compartment contains asolution consisting of sulfur dioxide,iodide,and an amine in asolvent containing methanol/chloroform or methanol/longerchain alcohol.In the cell with a diaphragm the cathodecompartment contains similar reagents optimized for cathodicreduction.4.Significance and Use4.1 Electrical characteristics of an insulating liquid may beaffected deleteriously by excessive water content.Ahigh water1This test method is under the jurisdiction of ASTM Committee D27 onElectrical Insulating Liquids and Gasesand is the direct responsibility of Subcom-mittee D27.06 on Chemical Test.Current edition approved Dec.1,2012.Published December 2012.Originallyapproved in 1958.Last previous edition approved in 2005 as D1533 00(2005).DOI:10.1520/D1533-12.2For 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 website.3American National Standards Institute,11 West 42nd Street,New York,NY100368002.4Scholz,E.,“Karl-Fischer Titration,”Springer-Verlag,Berlin,Heidelberg,NewYork,Tokyo,1984,140 pp.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 content may make a dielectric liquid unsuitable for someelectrical applications due to deterioration of properties such asthe dielectric breakdown voltage.4.2 These tests are suitable for use in acceptancespecifications,in control of processing,and in evaluating thecondition of dielectric liquids in service.5.Interferences5.1 Compounds such as aldehydes,ketones,free halogens,most acids,and oxidizing or reducing agents may interferewith coulometric Karl Fischer titrators.If a drifting end pointis noted,an alternative solvent system or another titrationmethod is warranted.If this drifting end point cannot becorrected,the water values should be regarded as s