Designation:E1750−10StandardGuideforUseofWaterTriplePointCells1ThisstandardisissuedunderthefixeddesignationE1750;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.INTRODUCTIONThetriplepointofwaterisanimportantthermometricfixedpointcommontothedefinitionoftwotemperaturescalesofscienceandtechnology,theKelvinThermodynamicTemperatureScale(KTTS)andtheInternationalTemperatureScaleof1990(ITS-90).TheITS-90wasdesignedtobeasclosetotheKTTSastheexperimentaldataavailableatthetimeoftheadoptionoftheITS-90wouldpermit.Thetemperatures(T)ontheKTTSaredefinedbyassigningthevalue273.16Ktothetriplepointofwater,thusdefiningthethermodynamicunitoftemperature,kelvin(K),as1/273.16ofthethermodynamictemperatureofthetriplepointofwater(1,2).2Thetriplepointofwater,oneofthefixedpointsusedtodefinetheITS-90,isthetemperaturetowhichtheresistanceratiosW(T)=R(T)⁄R(273.16K)ofthestandardplatinumresistancethermometer(SPRT)calibrationsarereferred.Thetriplepointsofvariousmaterials(wherethreedistinctphases,forexample,theirsolid,liquid,andvaporphases,coexistinastateofthermalequilibrium)havefixedpressuresandtemperaturesandarehighlyreproducible.OftheITS-90fixedpoints,sixaretriplepoints.ThewatertriplepointisoneofthemostaccuratelyrealizableofthedefiningfixedpointsoftheITS-90;underthebestofconditions,itcanberealizedwithanexpandeduncertainty(k=2)oflessthan60.00005K.Incomparison,itisdifficulttoprepareanduseanicebathwithanexpandeduncertainty(k=2)oflessthan60.002K(3).1.Scope1.1Thisguidecoversthenatureoftwocommercialwatertriple-pointcells(typesAandB,seeFig.1)andprovidesamethodforpreparingthecelltorealizethewatertriple-pointandcalibratethermometers.Testsforassuringtheintegrityofaqualifiedcellandofcellsyettobequalifiedaregiven.Precautionsforhandlingthecelltoavoidbreakagearealsodescribed.1.2Theeffectofhydrostaticpressu...
