S

Samplingrate591●SSSacrificialanode—isapieceofmetalusedasanan-odeinelectrochemicalprocesseswhereitisintendedtobedissolvedduringtheprocess.Incorrosionprotec-tionitisapieceofa“non-noble”metalormetalalloy(e.g.,magnesium,aluminum,zinc)attachedtothemetaltobeprotected.Becauseoftheirrelativeelectrodepo-tentialsthelatterisestablishedasthecathodeundthusimmunetocorrosion.Inelectroplatingthemetalusedasanodemayserveasasourceforreplenishingtheelectrolytewhichisconsumedbycathodicdeposition.Thesodium–leadalloyanodeusedintheelectrochemi-calproductionoftetraethylleadmayalsobeconsideredasasacrificialanode.RHSalinity—Theconventionalsalinity(S)ofseawaterisdefinedrelativetothechlorinity(Cl),whichisthechlo-rineequivalentofthetotalmassofhalidesthatcanbeprecipitatedfromkgofseawaterbytheadditionofsil-vernitrate.Therelationshipis:S=.Cl.Thetotalmassofdissolvedsolids(ST)isrelatedtothecon-ventionalsalinitybytheequation:ST=.S.Ref.:MilleroFJ()Seawaterasamulticomponentelectrolytesolution.In:GoldbergED(ed)Thesea,vol..Wiley,NewYork,pŠKLSaltbridge—Bringingtherespectiveelectrolytesolu-tionsoftwohalf-cellsintocontactwilloftenmakethedifferentsolventsand/orelectrolytesmeet.Thedifferentproperties,inparticularmobilitiesoftheparticipatingions,createaliquidjunctionpotential.Dependingontheactualcompositionoftheusedsolutionsseveraltenmillivoltscanbeobserved.Inordertoavoidthisunde-sirablecontributiontoacellvoltagemeasurementasaltbridgeisused.Thecommonprincipleofvariousavail-abletypesisatubeofaninertmaterialfilledwithasolu-tioncontaininganelectrolytewithapproximatelyequalmobilitiesofthecationandtheanion(e.g.,KNO,KCl)withtheendsofthetubeimmersedintheelectrolyteso-lutionofthehalfcells.Becausenomixingofthesolutionofthehalf-cellsoccursthiscannotcausealiquidjunc-tionpotential.Theliquidjunctionpotentialsestablishedatbothendsofthetubeofthesaltbridgemayevencan-celeachother.Typicaldesignsare:Seealsoflowingjunction,diffusionpotential,Lugginprobe,MacInnes.Saltbridge—FigureRefs.:[i]HolzeR()ElektrochemischesPraktikum.Teubner,Stuttgart;[ii]BardAJ,FaulknerLR()Electrochemicalmethods,ndedn.Wiley,NewYorkRHSample—Aspecimenorpartofagivenchemicalsys-temthatshowsthekindandqualityofthewhole[i].Ref.:[i]HarrisD()Quantitativechemicalanalysis.WHFreeman,NewYorkFGSamplemean(¯x)—Themeanofalimitedsetofdata[i].Ref.:[i]SkoogD,WestD,HollerF,CrouchS()Fundamentalsofanalyticalchemistry,thedn.Brooks/Cole,BelmontFGSampledcurrentvoltammetry—Voltammetryusingcurrentdataacquiredusingcurrentsampling(seecur-rentsampling).Recordingofcurrentresponsesformostvoltammetrictechniquesisbasedonsomeformofcurrentsampling.Anoldernameforsampledcurrentvoltammetryis‘tastvoltammetry’.AMBSamplingrate—Thespeedatwhichsamplesarereadandconvertedintoavoltageoradigitalexpression.TheNyquist’stheoremestablishesthatthesamplingratemustbegreaterthantwicethemaximumfrequencycomponentinthesignaltobeacquiredtoavoidthealiasingofdata[i].592Sandcell●SRef.:[i]EngineeringStaffAnalogDevicesInc.()Thedataconver-sionhandbook.Newness,OxfordFGSandcell—ThiswasessentiallyaCruikshankpilewheretheacidicsolutioninthetroughwassolidifiedwithsandsothatthebatterycouldeasilybetransported.Ref.:[i]HauckWP()DieGalvanischenBatterien,AccumulatorenundThermosäulen,ndedn.Hartleben’sVerlag,WienFSSandequation—Considerationoftheconcentrationc(x=,t)ataplanarworkingelectrodeincontactwithastagnant(unstirred)electrolytesolutionforareaction,wheretheoxidizedspeciesinthebulkispresentatacon-centrationcandthereducedspeciesisinitiallyabsentwithanappliedconstantcurrentI,yieldsc(x=,t)=c−ItnFADoxπfortheconcentrationc(x=,t)oftheoxidizedspeciesinfrontoftheelectrode(x=)asafunctionoftimet.Atacharacteristictimeτ(calledtransitiontime)c(x=,τ)dropstozero.AtthispointtheequationcanberewrittenIτc=nFADoxπ=.nNDoxAmAsmMwiththeelectrodesurfaceareaAincm.ThisequationiscalledSandequation[i].Aftertimeτhaspassed,thefluxofoxidizedspeciesnolongerwillsupporttheappliedcurrenti,andtheelectrodepotentialjumpstoanothervaluewhereanotherelectrodereactioncanproceed.Sandequation—FigureInatypicalexperimentemployingahangingmer-curydropelectrodeincontactwithanaqueoussolu-tionofmmolL−Cd(CHCOO)andmolL−KClatdifferentcurrents(asindicated)potential–timecurveswereobserved.Asexpectedtheproductofsquarerootoftransitiontimeandcurrentisconstant.Seealsochronopoten-tiometry.Refs.:[i]SandHJS()PhilosMag:;[ii]BardAJ,FaulknerLR()Electrochemicalmethods,ndedn.Wiley,NewYorkRHSatorycell—ThisbatterywasdevelopedbyKarlSatoryanditwasazinc–airbattery.Seealsozinc,Zn+/Znelectrodes,Zn+/Zn(Hg)electrodes,zinc–airbatteries(cell),andLeclanchécell.Ref.:[i]HauckWP()DieGalvanischenBatterien,AccumulatorenundThermosäulen,ndedn.Hartleben’sVerlag,WienFSSaturatedcalomelelectrodecalomelelectrodeSauerbrey-equationquartzcrystalmicrobalanceScanratepotentialsweeprateScanningelectrochemicalmicroscopy(SECM)—Ascanningprobetechniquethatisusedtoprobesurfacereactionsandalsoservesasanelectrochemicaltool.Itdiffersfromotherscanningprobemetho