chemical history of a candle, 1860 michael faraday

8/2/2019 Chemical History of a Candle, 1860 Michael Faraday

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ModernHistorySourcebook:TheChemicalHistoryofACandle,1860MichaelFaraday(1791-1867):

IntroductoryNote

MichaelFaradaywasthesonofablacksmith,andwasbornatNewingtonButts,nearLondon,September22,1791.Hebeganlifeasanerrandboytoabookbinderandstationer,towhomhewaslaterboundapprentice.Aftereightyearsinthisbusiness,hewasengagedbySirHumphryDavyashislaboratoryassistantattheRoyalInstitution,andin1813-15hetraveledextensivelyontheContinentwithhismaster,andsawsomeofthemostfamousscientistsofEurope.ShortlyafterhisreturntotheRoyalInstitution,hebegantomakecontributionsofhisowntoscience,hisfirstpaperappearingin1816.Hebecamedirectorofthelaboratoryin1825,andprofessorofchemistryin1833;risingrapidly,throughthenumberandimportanceofhisdiscoveries,toamostdistinguishedposition.Buthewasworkingattoogreatpressure,andin1841hishealthgaveway,sothatforsomethreeyearshecouldnotworkatall.Herecovered,however,andmadesomeofhismostimportantdiscoveriesafterthisinterruption;andwasoffered,butdeclined,thepresidencyofboththeRoyalSocietyandtheRoyalInstitution.HediedAugust25,1867.

ItwascharacteristicofFaraday'sdevotiontotheenlargementoftheboundsofhumanknowledgethatonhisdiscoveryofmagneto-electricityheabandonedth

ecommercialworkbywhichhehadaddedtohissmallsalary,inordertoreserveallhisenergiesforresearch.Thisfinanciallosswasinpartmadeuplaterbyapensionof300poundsayearfromtheBritishGovernment.

Faraday'sparentsweremembersoftheobscurereligiousdenominationoftheSandemanians,andFaradayhimself,shortlyafterhismarriage,attheageofthirty,joinedthesamesect,towhichheadheredtillhisdeath.Religionandsciencehekeptstrictlyapart,believingthatthedataofsciencewereofanentirelydifferentnaturefromthedirectcommunicationsbetweenGodandthesoulonwhichhisreligiousfaithwasbased.

ThediscoveriesmadebyFaradayweresonumerous,andoftendemandsodetailedaknowledgeofchemistryandphysicsbeforetheycanbeunderstood,thatiti

simpossibletoattempttodescribeorevenenumeratethemhere.Amongthemostimportantarethediscoveryofmagneto-electricinduction,ofthelawofelectro-chemicaldecomposition,ofthemagnetizationoflight,andofdiamagnetism.Roundeachofthesearegroupednumbersofderivativebutstillhighlyimportantadditionstoscientificknowledge,andtogethertheyformsovastanachievementastoleadhissuccessor,Tyndall,tosay,"Takinghimforallandall,IthinkitwillbeconcededthatMichaelFaradaywasthegreatestexperimentalphilosophertheworldhaseverseen;andIwilladdtheopinion,thattheprogressoffutureresearchwilltend,nottodimortodiminish,buttoenhanceandglorifythelaboursofthismightyinvestigator."

Inspiteofthehighlytechnicalnatureofhisworkinresearch,Faradaywasremarkablygiftedasanexpounderofsciencetopopularaudiences;andhislect

uresattheRoyalInstitution,especiallythosetoyoungeraudiences,werejustlyfamous.Thefollowingexampleisaclassicinthedepartmentofclearandfascinatingscientificexposition.

*LectureI:ACandle:TheFlame-ItsSources-StructureMobility-Brightness*LectureII:BrightnessofTheFlame-AirNecessaryForCombustion-ProductionofWater*LectureIII:Products:WaterFromTheCombustion-NatureofWater-ACompound-Hydrogen


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*LectureIV:HydrogeninTheCandle-BurnsIntoWater-TheOtherPartofWater-Oxygen*LectureV:OxygenPresentinTheAir-NatureofTheAtmosphere-CarbonicAcid*LectureVI:CarbonorCharcoal-CoalGas-RespirationandItsAnalogytoACandle

LectureI:ACandle:TheFlame-ItsSources-StructureMobility-Brightness

Ipurpose,inreturnforthehonoryoudousbycomingtoseewhatareourproceedingshere,tobringbeforeyou,inthecourseoftheselectures,theChemicalHistoryofaCandle.Ihavetakenthissubjectonaformeroccasion,and,wereitlefttomyownwill,Ishouldprefertorepeatitalmosteveryyear,soabundantistheinterestthatattachesitselftothesubject,sowonderfularethevarietiesofoutletwhichitoffersintothevariousdepartmentsofphilosophy.Thereisnotalawunderwhichanypartofthisuniverseisgovernedwhichdoesnotcomeintoplayandistoucheduponinthesephenomena.Thereisnobetter,thereisnomoreopendoorbywhichyoucanenterintothestudyofnaturalphilosophythanbyconsideringthephysicalphenomenaofacandle.Itrust,therefore,Ishallnotdisappointyouinchoosingthisformysubjectratherthananynewertopic,whichcouldnotbebetter,wereitevensogood.

And,beforeproceeding,letmesaythisalso:that,thoughoursubjectbeso

great,andourintentionthatoftreatingithonestly,seriously,andphilosophically,yetImeantopassawayfromallthosewhoareseniorsamongus.Iclaimtheprivilegeofspeakingtojuvenilesasajuvenilemyself.Ihavedonesoonformeroccasions,and,ifyouplease,Ishalldosoagain.And,thoughIstandherewiththeknowledgeofhavingthewordsIuttergiventotheworld,yetthatshallnotdetermefromspeakinginthesamefamiliarwaytothosewhomIesteemnearesttomeonthisoccasion.

Andnow,myboysandgirls,Imustfirsttellyouofwhatcandlesaremade.Somearegreatcuriosities.Ihaveheresomebitsoftimber,branchesoftreesparticularlyfamousfortheirburning.Andhereyouseeapieceofthatverycurioussubstance,takenoutofsomeofthebogsinIreland,calledcandle-wood;ahard,strong,excellentwood,evidentlyfittedforgoodworkasaregisteroffor

ce,andyet,withal,burningsowellthatwhereitisfoundtheymakesplintersofit,andtorches,sinceitburnslikeacandle,andgivesaverygoodlightindeed.AndinthiswoodwehaveoneofthemostbeautifulillustrationsofthegeneralnatureofacandlethatIcanpossiblygive.Thefuelprovided,themeansofbringingthatfueltotheplaceofchemicalaction,theregularandgradualsupplyofairtothatplaceofaction-heatandlight-allproducedbyalittlepieceofwoodofthiskind,forming,infact,anaturalcandle.

Butwemustspeakofcandlesastheyareincommerce.Hereareacoupleofcandlescommonlycalleddips.Theyaremadeoflengthsofcottoncutoff,hungupbyaloop,dippedintomeltedtallow,takenoutagainandcooled,thenredipped,untilthereisanaccumulationoftallowroundthecotton.Inorderthatyoumayhaveanideaofthevariouscharactersofthesecandles,youseethesewhich

Iholdinmyhand-theyareverysmallandverycurious.Theyare,orwere,thecandlesusedbytheminersincoalmines.Inoldentimestheminerhadtofindhisowncandles,anditwassupposedthatasmallcandlewouldnotsosoonsetfiretothefire-dampinthecoalminesasalargeone;andforthatreason,aswellasforeconomy'ssake,hehadcandlesmadeofthissort-20,30,40,or60tothepound.Theyhavebeenreplacedsincethenbythesteel-mill,andthenbytheDavylamp,andothersafetylampsofvariouskinds.IhavehereacandlethatwastakenoutoftheRoyalGeorge1,itissaid,byColonelPasley.Ithasbeensunkintheseaformanyyears,subjecttotheactionofsaltwater.Itshowsyouhowwellcandlesmaybepreserved;for,thoughitiscrackedaboutandbroke


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nagreatdeal,yetwhenlighteditgoesonburningregularly,andthetallowresumesitsnaturalconditionassoonasitisfused.

[Footnote1:TheRoyalGeorgesunkatSpitheadonthe29thofAugust,1782.ColonelPasleycommencedoperationsfortheremovalofthewreckbytheexplosionofgunpowder,inAugust1839.ThecandlewhichProfessorFaradayexhibitedmustthereforehavebeenexposedtotheactionofsaltwaterforupwardoffifty-sevenyears.]

Mr.Field,ofLambeth,hassuppliedmeabundantlywithbeautifulillustrationsofthecandleanditsmaterials;Ishallthereforenowrefertothem.And,first,thereisthesuet-thefatoftheox-Russiantallow,Ibelieve,employedinthemanufactureofthesedips,whichGay-Lussac,orsomeonewhointrustedhimwithhisknowledge,convertedintothatbeautifulsubstance,stearin,whichyouseelyingbesideit.Acandle,youknow,isnotnowagreasythinglikeanordinarytallowcandle,butacleanthing,andyoumayalmostscrapeoffandpulverizethedropswhichfallfromitwithoutsoilinganything.Thisistheprocessheadopted2:Thefatortallowisfirstboiledwithquick-lime,andmadeintoasoap,andthenthesoapisdecomposedbysulphuricacid,whichtakesawaythelime,andleavesthefatrearrangedasstearicacid,whileaquantityofglycerinisproducedatthesametime.Glycerin-absolutelyasugar,orasubstancesimilartosugarcomesoutofthetallowinthischemicalchange.Theoilisthenpressedoutofit;andyouseeherethisseriesofpressedcakes,showinghowbeautifullytheimpuritiesarecarriedoutbytheoilypartasthepressuregoeso

nincreasing,andatlastyouhaveleftthatsubstance,whichismelted,andcastintocandlesashererepresented.ThecandleIhaveinmyhandisastearincandle,madeofstearinfromtallowinthewayIhavetoldyou.Thenhereisaspermcandle,whichcomesfromthepurifiedoilofthespermacetiwhale.Here,also,areyellowbeeswaxandrefinedbeeswax,fromwhichcandlesaremade.Here,too,isthatcurioussubstancecalledparaffine,andsomeparaffinecandles,madeofparaffineobtainedfromthebogsofIreland.IhaveherealsoasubstancebroughtfromJapansincewehaveforcedanentranceintothatout-of-the-wayplace-asortofwaxwhichakindfriendhassentme,andwhichformsanewmaterialforthemanufactureofcandles.

[Footnote2:Thefatortallowconsistsofachemicalcombinationoffattyacidswithglycerin.Thelimeuniteswiththepalmitic,oleic,andstearicac

ids,andseparatestheglycerin.Afterwashing,theinsolublelimesoapisdecomposedwithhotdilutesulphuricacid.Themeltedfattyacidsthusriseasanoiltothesurface,whentheyaredecanted.Theyareagainwashedandcastintothinplates,which,whencold,areplacedbetweenlayersofcocoanutmattingandsubmittedtointensehydraulicpressure.Inthiswaythesoftoleicacidissqueezedout,whilethehardpalmiticandstearicacidsremain.Thesearefartherpurifiedbypressureatahighertemperatureandwashinginwarmdilutesulphuricacid,whentheyarereadytobemadeintocandles.Theseacidsareharderandwhiterthanthefatsfromwhichtheywereobtained,whileatthesametimetheyarecleanerandmorecombustible.]

Andhowarethesecandlesmade?Ihavetoldyouaboutdips,andIwillshowyouhowmouldsaremade.Letusimagineanyofthesecandlestobemadeofmater

ialswhichcanbecast."Cast!"yousay."Why,acandleisathingthatmelts,andsurelyifyoucanmeltityoucancastit."Notso.Itiswonderful,intheprogressofmanufacture,andintheconsiderationofthemeansbestfittedtoproducetherequiredresult,howthingsturnupwhichonewouldnotexpectbeforehand.Candlescannotalwaysbecast.Awaxcandlecanneverbecast.ItismadebyaparticularprocesswhichIcanillustrateinaminuteortwo,butImustnotspendmuchtimeonit.Waxisathingwhich,burningsowell,andmeltingsoeasilyinacandle,cannotbecast.However,letustakeamaterialthatcanbecast.Hereisaframe,withanumberofmouldsfastenedinit.Thefirstthingtobedoneistoputawickthroughthem.Hereisone-aplaitedwick,whichdoes


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notrequiresnuffing3supportedbyalittlewire.Itgoestothebottom,whereitispeggedin-thelittlepegholdingthecottontight,andstoppingtheaperturesothatnothingfluidshallrunout.Attheupperpartthereisalittlebarplacedacross,whichstretchesthecottonandholdsitinthemould.Thetallowisthenmelted,andthemouldsarefilled.Afteracertaintime,whenthemouldsarecool,theexcessoftallowispouredoffatonecorner,andthencleanedoffaltogether,andtheendsofthewickcutaway.Thecandlesalonethenremaininthemould,andyouhaveonlytoupsetthem,asIamdoing,whenouttheytumble,forthecandlesaremadeintheformofcones,beingnarroweratthetopthanatthebottom:sothat,whatwiththeirformandtheirownshrinking,theyonlyneedalittleshaking,andouttheyfall.Inthesamewayaremadethesecandlesofstearinandofparaffine.Itisacuriousthingtoseehowwaxcandlesaremade.Alotofcottonsarehunguponframes,asyouseehere,andcoveredwithmetaltagsattheendstokeepthewaxfromcoveringthecottoninthoseplaces.Thesearecarriedtoaheater,wherethewaxismelted.Asyousee,theframescanturnround;and,astheyturn,amantakesavesselofwaxandpoursitfirstdownone,andthenthenext,andthenext,andsoon.Whenhehasgoneonceround,ifitissufficientlycool,hegivesthefirstasecondcoat,andsoonuntiltheyarealloftherequiredthickness.Whentheyhavebeenthusclothed,orfed,ormadeuptothatthickness,theyaretakenoffandplacedelsewhere.Ihavehere,bythekindnessofMr.Field,severalspecimensofthesecandles.Hereisoneonlyhalf-finished.Theyarethentakendownandwellrolleduponafinestoneslab,andtheconicaltopismouldedbyproperlyshapedtubes,andthebottomscutoffandtrimmed.Thisisdonesobeautifullythattheycanmakecandl

esinthiswayweighingexactlyfourorsixtothepound,oranynumbertheyplease.

[Footnote3:Alittleboraxorphosphorussaltissometimeaddedinordertomaketheashfusible.]

Wemustnot,however,takeupmoretimeaboutthemeremanufacture,butgoalittlefartherintothematter.Ihavenotyetreferredyoutoluxuriesincandles(forthereissuchathingasluxuryincandles).Seehowbeautifullythesearecolored;youseeheremauve,magenta,andallthechemicalcolorsrecentlyintroduced,appliedtocandles.Youobserve,also,differentformsemployed.Hereisaflutedpillarmostbeautifullyshaped;andIhavealsoheresomecandlessentmebyMr.Pearsall,whichareornamentedwithdesignsuponthem,sothat,as

theyburn,youhave,asitwere,aglowingsunabove,andbouquetofflowersbeneath.All,however,thatisfineandbeautifulisnotuseful.Theseflutedcandles,prettyastheyare,arebadcandles;theyarebadbecauseoftheirexternalshape.Nevertheless,Ishowyouthesespecimens,senttomefromkindfriendsonallsides,thatyoumayseewhatisdoneandwhatmaybedoneinthisorthatdirection;although,asIhavesaid,whenwecometotheserefinements,weareobligedtosacrificealittleinutility.

Nowastothelightofthecandle.Wewilllightoneortwo,andsetthematworkintheperformanceoftheirproperfunctions.Youobserveacandleisaverydifferentthingfromalamp.Withalampyoutakealittleoil,fillyourvessel,putinalittlemossorsomecottonpreparedbyartificialmeans,andthenlightthetopofthewick.Whentheflamerunsdownthecottontotheoil,itge

tsextinguished,butitgoesonburninginthepartabove.NowIhavenodoubtyouwillaskhowitisthattheoilwhichwillnotburnofitselfgetsuptothetopofthecotton,whereitwillburn.Weshallpresentlyexaminethat;butthereisamuchmorewonderfulthingabouttheburningofacandlethanthis.Youhavehereasolidsubstancewithnovesseltocontainit;andhowisitthatthissolidsubstancecangetuptotheplacewheretheflameis?Howisitthatthissolidgetsthere,itnotbeingafluid?or,whenitismadeafluid,thenhowisitthatitkeepstogether?Thisisawonderfulthingaboutacandle.

Wehavehereagooddealofwind,whichwillhelpusinsomeofourillustra


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tions,butteaseusinothers;forthesake,therefore,ofalittleregularity,andtosimplifythematter,Ishallmakeaquietflame,forwhocanstudyasubjectwhentherearedifficultiesinthewaynotbelongingtoit?Hereisacleverinventionofsomecostermongerorstreet-standerinthemarket-placefortheshadingoftheircandlesonSaturdaynights,whentheyaresellingtheirgreens,orpotatoes,orfish.Ihaveveryoftenadmiredit.Theyputalamp-glassroundthecandle,supportedonakindofgallery,whichclaspsit,anditcanbeslippedupanddownasrequired.Bytheuseofthislamp-glass,employedinthesameway,youhaveasteadyflame,whichyoucanlookat,andcarefullyexamine,asIhopeyouwilldo,athome.

Yousee,then,inthefirstinstance,thatabeautifulcupisformed.Astheaircomestothecandle,itmovesupwardbytheforceofthecurrentwhichtheheatofthecandleproduces,anditsocoolsallthesidesofthewax,tallow,orfuelastokeeptheedgemuchcoolerthanthepartwithin;thepartwithinmeltsbytheflamethatrunsdownthewickasfarasitcangobeforeitisextinguished,butthepartontheoutsidedoesnotmelt.IfImadeacurrentinonedirection,mycupwouldbelop-sided,andthefluidwouldconsequentlyrunover;forthesameforceofgravitywhichholdsworldstogetherholdsthisfluidinahorizontalposition,andifthecupbenothorizontal,ofcoursethefluidwillrunawayinguttering.Yousee,therefore,thatthecupisformedbythisbeautifullyregularascendingcurrentofairplayinguponallsides,whichkeepstheexteriorofthecandlecool.Nofuelwouldserveforacandlewhichhasnotthepropertyofgivingthiscup,exceptsuchfuelastheIrishbogwood,wherethemater

ialitselfislikeaspongeandholdsitsownfuel.YouseenowwhyyouwouldhavehadsuchabadresultifyouweretoburnthesebeautifulcandlesthatIhaveshownyou,whichareirregular,intermittentintheirshape,andcannot,therefore,havethatnicely-formededgetothecupwhichisthegreatbeautyinacandle.Ihopeyouwillnowseethattheperfectionofaprocess-thatis,itsutility-isthebetterpointofbeautyaboutit.Itisnotthegestlookingthing,butthebestactingthing,whichisthemostadvantageoustous.Thisgood-lookingcandleisabad-burningone.Therewillbeagutteringroundaboutitbecauseoftheirregularityofthestreamofairandthebadnessofthecupwhichisformedthereby.Youmayseesomeprettyexamples(andItrustyouwillnoticetheseinstances)oftheactionoftheascendingcurrentwhenyouhavealittlegutterrundownthesideofacandle,makingitthickertherethanitiselsewhere.Asthecandlegoesonburning,thatkeepsitsplaceandformsalittlepillarst

ickingupbytheside,because,asitriseshigherabovetherestofthewaxorfuel,theairgetsbetterroundit,anditismorecooledandbetterabletoresisttheactionoftheheatatalittledistance.Nowthegreatestmistakesandfaultswithregardtocandles,asinmanyotherthings,oftenbringwiththeminstructionwhichweshouldnotreceiveiftheyhadnotoccurred.Wecomeheretobephilosophers,andIhopeyouwillalwaysrememberthatwheneveraresulthappens,especiallyifitbenew,youshouldsay,"Whatisthecause?Whydoesitoccur?"andyouwill,inthecourseoftime,findoutthereason.

Thenthereisanotherpointaboutthesecandleswhichwillansweraquestion-thatis,astothewayinwhichthisfluidgetsoutofthecup,upthewick,andintotheplaceofcombustion.Youknowthattheflamesontheseburningwicksincandlesmadeofbeeswax,stearin,orspermaceti,donotrundowntothewax

orothermatter,andmeltitallaway,butkeeptotheirownrightplace.Theyarefencedofffromthefluidbelow,anddonotencroachonthecupatthesides.Icannotimagineamorebeautifulexamplethantheconditionofadjustmentunderwhichacandlemakesonepartsubservetotheothertotheveryendofitsaction.Acombustiblethinglikethat,burningawaygradually,neverbeingintrudeduponbytheflame,isaverybeautifulsight,especiallywhenyoucometolearnwhatavigorousthingflameis-whatpowerithasofdestroyingthewaxitselfwhenitgetsholdofit,andofdisturbingitsproperformifitcomeonlytoonear.


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Buthowdoestheflamegetholdofthefuel?Thereisabeautifulpointaboutthat-capillaryattraction.4"Capillaryattraction!"yousay-"theattractionofhairs."Well,nevermindthename;itwasgiveninoldtimes,beforewehadagoodunderstandingofwhattherealpowerwas.Itisbywhatiscalledcapillaryattractionthatthefuelisconveyedtothepartwherecombustiongoeson,andisdepositedthere,notinacarelessway,butverybeautifullyintheverymidstofthecentreofaction,whichtakesplacearoundit.NowIamgoingtogiveyouoneortwoinstancesofcapillaryattraction.Itisthatkindofactionorattractionwhichmakestwothingsthatdonotdissolveineachotherstillholdtogether.Whenyouwashyourhands,youwetthemthoroughly;youtakealittlesoaptomaketheadhesionbetter,andyoufindyourhandsremainwet.ThisisbythatkindofattractionofwhichIamabouttospeak.And,whatismore,ifyourhandsarenotsoiled(astheyalmostalwaysarebytheusagesoflife),ifyouputyourfingerintoalittlewarmwater,thewaterwillcreepalittlewayupthefinger,thoughyoumaynotstoptoexamineit.Ihavehereasubstancewhichisratherporous-acolumnofsalt-andIwillpourintotheplateatthebottom,notwater,asitappears,butasaturatedsolutionofsaltwhichcannotabsorbmore,sothattheactionwhichyouseewillnotbeduetoitsdissolvinganything.Wemayconsidertheplatetobethecandle,andthesaltthewick,andthissolutionthemeltedtallow.(Ihavecoloredthefluid,thatyoumayseetheactionbetter.)Youobservethat,nowIpourinthefluid,itrisesandgraduallycreepsupthesalthigherandhigher;andprovidedthecolumndoesnottumbleover,itwillgotothetop.Ifthisbluesolutionwerecombustible,andweweretoplaceawickatthetopofthesalt,itwouldburnasitenteredintothe

wick.Itisamostcuriousthingtoseethiskindofactiontakingplace,andtoobservehowsingularsomeofthecircumstancesareaboutit.Whenyouwashyourhands,youtakeatoweltowipeoffthewater;anditisbythatkindofwetting,orthatkindofattractionwhichmakesthetowelbecomewetwithwater,thatthewickismadewetwiththetallow.Ihaveknownsomecarelessboysandgirls(indeed,Ihaveknownithappentocarefulpeopleaswell)who,havingwashedtheirhandsandwipedthemwithatowel,havethrownthetoweloverthesideofthebasin,andbeforelongithasdrawnallthewateroutofthebasinandconveyedittothefloor,becauseithappenedtobethrownoverthesideinsuchawayastoservethepurposeofasiphon.5Thatyoumaythebetterseethewayinwhichthesubstancesactoneuponanother,Ihavehereavesselmadeofwiregauzefilledwithwater,andyoumaycompareitinitsactiontothecottoninonerespect,ortoapieceofcalicointheother.Infact,wicksaresometimesmadeo

fakindofwiregauze.Youwillobservethatthisvesselisaporousthing;forifIpouralittlewaterontothetop,itwillrunoutatthebottom.YouwouldbepuzzledforagoodwhileifIaskedyouwhatthestateofthisvesselis,whatisinsideit,andwhyitisthere?Thevesselsisfullofwater,andyetyouseethewatergoesinandrunsoutasifitwereempty.Inordertoprovethistoyou,Ihaveonlytoemptyit.Thereasonisthis:thewire,beingoncewetted,remainswet;themeshesaresosmallthatthefluidisattractedsostronglyfromtheonesidetotheother,astoremaininthevessel,althoughitisporous.Inlikemanner,theparticlesofmeltedtallowascendthecottonandgettothetop:otherparticlesthenfollowbytheirmutualattractionforeachother,andastheyreachtheflametheyaregraduallyburned.

[Footnote4:Capillaryattractionorrepulsionisthecausewhichdeterm

inestheascentordescentofafluidinacapillarytube.Ifapieceofthermometertubing,openateachend,beplungedintowater,thelatterwillinstantlyriseinthetubeconsiderablyaboveitsexternallevel.If,ontheotherhand,thetubebeplungedintomercury,arepulsioninsteadofattractionwillbeexhibited,andthelevelofthemercurywillbelowerinthetubethanitisoutside.]

[Footnote5:ThelateDukeofSussexwas,webelieve,thefirsttoshowthataprawnmightbewasheduponthisprinciple.Ifthetail,afterpullingoffthefanpart,beplacedinatumblerofwater,andtheheadbeallowedtohang


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overtheoutside,thewaterwillbesuckedupthetailbycapillaryattraction,andwillcontinuetorunoutthroughtheheaduntilthewaterintheglasshassunksolowthetailceasestodipintoit.]

Hereisanotherapplicationofthesameprinciple.Youseethisbitofcane.Ihaveseenboysaboutthestreets,whoareveryanxioustoappearlikemen,takeapieceofcane,andlightit,andsmokeit,asanimitationofacigar.Theyareenabletodosobythepermeabilityofthecaneinonedirection,andbyitscapillarity.IfIplacethispieceofcaneonaplatecontainingsomecamphene(whichisverymuchlikeparaffineinitsgeneralcharacter),exactlyinthesamemannerasthebluefluidrosethroughthesaltwillthisfluidrisethroughthepieceofcane.Therebeingnoporesattheside,thefluidcannotgointhatdirection,butmustpassthroughitslength.Alreadythefluidisatthetopofthecane;nowIcanlightitandmakeitserveasacandle.Thefluidhasrisenbythecapillaryattractionofthepieceofcane,justasitdoesthroughthecottoninthecandle.

Nowtheonlyreasonwhythecandledoesnotburnalldownthesideofthewickisthatthemeltedtallowextinguishestheflame.Youknowthatacandle,ifturnedupsidedown,soastoallowthefueltorunuponthewick,willbeputout.Thereasonis,thattheflamehasnothadtimetomakethefuelhotenoughtoburn,asitdoesabove,whereitiscarriedinsmallquantitiesintothewick,andhasalltheeffectoftheheatexerciseduponit.

Thereisanotherconditionwhichyoumustlearnasregardsthecandle,withoutwhichyouwouldnotbeablefullytounderstandthephilosophyofit,andthatisthevaporousconditionofthefuel.Inorderthatyoumayunderstandthat,letmeshowyouaveryprettybutverycommonplaceexperiment.Ifyoublowacandleoutcleverly,youwillseethevaporrisefromit.Youhave,Iknow,oftensmeltthevaporofablown-outcandle,andaverybadsmellitis;butifyoublowitoutcleverlyyouwillbeabletoseeprettywellthevaporintowhichthissolidmatteristransformed.Iwillblowoutoneofthesecandlesinsuchawayasnottodisturbtheairarounditbythecontinuingactionofmybreath;andnow,ifIholdalightedtapertwoorthreeinchesfromthewick,youwillobserveatrainoffiregoingthroughtheairtillitreachesthecandle.Iamobligedtobequickandready,becauseifIallowthevaportimetocool,itbecomescondensedintoaliquidorsolid,orthestreamofcombustiblemattergetsdisturb

ed.

Nowastotheshapeorformoftheflame.Itconcernsusmuchtoknowabouttheconditionwhichthematterofthecandlefinallyassumesatthetopofthewick,whereyouhavesuchbeautyandbrightnessasnothingbutcombustionorflamecanproduce.Youhavetheglitteringbeautyofgoldandsilver,andthestillhigherlustreofjewelsliketherubyanddiamond;butnoneoftheserivalthebrilliancyandbeautyofflame.Whatdiamondcanshinelikeflame?Itowesitslustreatnighttimetotheveryflameshininguponit.Theflameshinesindarkness,butthelightwhichthediamondhasisasnothinguntiltheflameshinesuponit,whenitisbrilliantagain.Thecandlealoneshinesbyitselfandforitself,orforthosewhohavearrangedthematerials.Nowletuslookalittleattheformoftheflameasyouseeitundertheglassshade.Itissteadyandequal,

anditsgeneralformisthatwhichisrepresentedinthediagram,varyingwithatmosphericdisturbances,andalsovaryingaccordingtothesizeofthecandle.Itisabrightoblong,brighteratthetopthantowardthebottom,withthewickinthemiddle,and,besidesthewickinthemiddle,certaindarkerpartstowardsthebottom,wheretheignitionisnotsoperfectasinthepartabove.Ihaveadrawinghere,sketchedmanyyearsagobyHooker,whenhemadehisinvestigations.Itisthedrawingoftheflameofalamp,butitwillapplytotheflameofacandle.Thecupofthecandleisthevesselorlamp;themeltedspermacetiistheoil;andthewickiscommontoboth.Uponthathesetsthislittleflame,andthenherepresentswhatistrue,acertainquantityofmatterrisingaboutitw


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hichyoudonotsee,andwhich,ifyouhavenotbeenherebefore,orarenotfamiliarwiththesubject,youwillnotknowof.Hehashererepresentedthepartsofthesurroundingatmospherethatareveryessentialtotheflame,andthatarealwayspresentwithit.Thereisacurrentformed,whichdrawstheflameout;fortheflamewhichyouseeisreallydrawnoutbythecurrent,anddrawnupwardtoagreatheight,justasHookerhashereshownyoubythatprolongationofthecurrentinthediagram.Youmayseethisbytakingalightedcandle,andputtingitinthesunsoastogetitsshadowthrownonapieceofpaper.Howremarkableitisthatthatthingwhichislightenoughtoproduceshadowsofotherobjectscanbemadetothrowitsownshadowonapieceofwhitepaperorcard,sothatyoucanactuallyseestreamingroundtheflamesomethingwhichisnotpartoftheflame,butisascendinganddrawingtheflameupward.NowIamgoingtoimitatethesunlightbyapplyingthevoltaicbatterytotheelectriclamp.Younowseeoursunanditsgreatluminosity;andbyplacingacandlebetweenitandthescreen,wegettheshadowoftheflame.Youobservetheshadowofthecandleandofthewick;thenthereisadarkishpart,asrepresentedinthediagram,andthenapartwhichismoredistinct.Curiouslyenough,however,whatweseeintheshadowasthedarkestpartoftheflameis,inreality,thebrightestpart;andhereyouseestreamingupwardtheascendingcurrentofhotair,asshownbyHooker,whichdrawsouttheflame,suppliesitwithair,andcoolsthesidesofthecupofmeltedfuel.

Icangiveyouherealittlefartherillustration,forthepurposeofshowingyouhowflamegoesupordownaccordingtothecurrent.Ihavehereaflame-

itisnotacandleflame-butyoucan,nodoubt,bythistimegeneralizeenoughtobeabletocompareonethingwithanother.WhatIamabouttodoistochangetheascendingcurrentthattakestheflameupwardintoadescendingcurrent.ThisIcaneasilydobythelittleapparatusyouseebeforeme.Theflame,asIhavesaid,isnotacandleflame,butitisproducedbyalcohol,sothatitshallnotsmoketoomuch.Iwillalsocolortheflamewithanothersubstance6,sothatyoumaytraceitscourse;for,withthespiritalone,youcouldhardlyseewellenoughtohavetheopportunityoftracingitsdirection.Bylightingthisspiritofwinewehavethenaflameproduced,andyouobservethatwhenheldintheairitnaturallygoesupward.Youunderstandnow,easilyenough,whyflamesgoupunderordinarycircumstances:itisbecauseofthedraughtofairbywhichthecombustionisformed.Butnow,byblowingtheflamedown,youseeIamenabledtomakeitgodownwardintothislittlechimney,thedirectionofthecurrentb

eingchanged.Beforewehaveconcludedthiscourseoflecturesweshallshowyoualampinwhichtheflamegoesupandthesmokegoesdown,ortheflamegoesdownandthesmokegoesup.Yousee,then,thatwehavethepowerinthiswayofvaryingtheflameindifferentdirections.

[Footnote6:Thealcoholhadchlorideofcopperdissolvedinit:thisproducesabeautifulgreenflame.]

TherearenowsomeotherpointsthatImustbringbeforeyou.Manyoftheflamesyouseeherevaryverymuchintheirshapebythecurrentsofairblowingaroundthemindifferentdirections;butwecan,ifwelike,makeflamessothattheywilllooklikefixtures,andwecanphotographthemindeed,wehavetophotographthem-sothattheybecomefixedtous,ifwewishtofindouteverythin

gconcerningthem.That,however,isnottheonlythingIwishtomention.IfItakeaflamesufficientlylarge,itdoesnotkeepthathomogeneous,thatuniformconditionofshape,butitbreaksoutwithapoweroflifewhichisquitewonderful.Iamabouttouseanotherkindoffuel,butonewhichistrulyandfairlyarepresentativeofthewaxortallowofacandle.Ihaveherealargeballofcotton,whichwillserveasawick.And,nowthatIhaveimmerseditinspiritandappliedalighttoit,inwhatwaydoesitdifferfromanordinarycandle?Why,itdiffersverymuchinonerespect,thatwehaveavivacityandpoweraboutit,abeautyandalifeentirelydifferentfromthelightpresentedbyacandle.Youseethosefinetonguesofflamerisingup.Youhavethesamegeneraldisposi


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tionofthemassoftheflamefrombelowupward;but,inadditiontothat,youhavethisremarkablebreakingoutintotongueswhichyoudonotperceiveinthecaseofacandle.Now,whyisthis?Imustexplainittoyou,because,whenyouunderstandthatperfectly,youwillbeabletofollowmebetterinwhatIhavetosayhereafter.IsupposesomeherewillhavemadeforthemselvestheexperimentIamgoingtoshowyou.AmIrightinsupposingthatanybodyherehasplayedatsnapdragon?Idonotknowamorebeautifulillustrationofthephilosophyofflame,astoacertainpartofitshistory,thanthegameofsnapdragon.First,hereisthedish;andletmesay,thatwhenyouplaysnapdragonproperlyyououghttohavethedishwellwarmed;yououghtalsotohavewarmplums,andwarmbrandy,which,however,Ihavenotgot.Whenyouhaveputthespiritintothedish,youhavethecupandthefuel;andarenottheraisinsactinglikethewicks?Inowthrowtheplumsintothedish,andlightthespirit,andyouseethosebeautifultonguesofflamethatIreferto.Youhavetheaircreepinginovertheedgeofthedishformingthesetongues.Why?Because,throughtheforceofthecurrentandtheirregularityoftheactionoftheflame,itcannotflowinoneuniformstream.Theairflowsinsoirregularlythatyouhavewhatwouldotherwisebeasingleimagebrokenupintoavarietyofforms,andeachoftheselittletongueshasanindependentexistenceofitsown.Indeed,Imightsay,youhavehereamultitudeofindependentcandles.Youmustnotimagine,becauseyouseethesetonguesallatonce,thattheflameisofthisparticularshape.Aflameofthatshapeisneversoatanyonetime.Neverisabodyofflame,likethatwhichyoujustsawrisingfromtheball,oftheshapeitappearstoyou.Iconsistsofamultitudeofdifferentshapes,succeedingeachothersofastthattheeyeiso

nlyabletotakecognizanceofthemallatonce.InformertimesIpurposelyanalyzedaflameofthatgeneralcharacter,andthediagramshowsyouthedifferentpartsofwhichitiscomposed.Theydonotoccurallatonce;itisonlybecauseweseetheseshapesinsuchrapidsuccessionthattheyseemtoustoexistallatonetime.

Itistoobadthatwehavenotgotfartherthanmygameofsnapdragon;butwemustnot,underanycircumstances,keepyoubeyondyourtime.Itwillbealessontomeinfuturetoholdyoumorestrictlytothephilosophyofthethingthantotakeupyourtimesomuchwiththeseillustrations.

LectureII:BrightnessOfTheFlame-AirNecessaryForCombustion-Product

ionOfWater

Wewereoccupiedthelasttimewemetinconsideringthegeneralcharacterandarrangementasregardsthefluidportionofacandle,andthewayinwhichthatfluidgotintotheplaceofcombustion.Yousee,whenwehaveacandleburningfairlyinaregular,steadyatmosphere,itwillhaveashapesomethingliketheoneshowninthediagram,andwilllookprettyuniform,althoughverycuriousinitscharacter.AndnowIhavetoaskyourattentiontothemeansbywhichweareenabledtoascertainwhathappensinanyparticularpartoftheflame;whyithappens;whatitdoesinhappening;andwhere,afterall,thewholecandlegoesto;because,asyouknowverywell,acandlebeingbroughtbeforeusandburned,disappears,ifburnedproperly,withouttheleasttraceofdirtinthecandlestick,andthisisaverycuriouscircumstance.Inorder,then,toexaminethis

candlecarefully,Ihavearrangedcertainapparatus,theuseofwhichyouwillseeasIgoon.Hereisacandle;Iamabouttoputtheendofthisglasstubeintothemiddleoftheflame-intothatpartwhicholdHookerhasrepresentedinthediagramasbeingratherdark,andwhichyoucanseeatanytimeifyouwilllookatacandlecarefully,withoutblowingitabout.Wewillexaminethisdarkpartfirst.

NowItakethisbentglasstube,andintroduceoneendintothatpartoftheflame,andyouseeatoncethatsomethingiscomingfromtheflame,outattheotherendofthetube;andifIputaflaskthere,andleaveitforalittlewhi


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le,youwillseethatsomethingfromthemiddlepartoftheflameisgraduallydrawnout,andgoesthroughthetube,andintothatflask,andtherebehavesverydifferentlyfromwhatitdoesintheopenair.Itnotonlyescapesfromtheendofthetube,butfallsdowntothebottomoftheflasklikeaheavysubstance,asindeeditis.Wefindthatthisisthewaxofexperiment,ifthereisnottoomuchdisturbance,therewillalwaysbearing.Thisisagoodexperimentforyoutomakeathome.Takeastripofpaper,havetheairintheroomquiet,andputthepieceofpaperrightacrossthemiddleoftheflame-(ImustnottalkwhileImaketheexperiment)-andyouwillfindthatitisburntintwoplaces,andthatitisnotburnt,orverylittleso,inthemiddle;andwhenyouhavetriedtheexperimentonceortwice,soastomakeitnicely,youwillbeveryinterestedtoseewheretheheatis,andtofindthatitiswheretheairandthefuelcometogether.

Thisismostimportantforusasweproceedwithoutsubject.Airisabsolutelynecessaryforcombustion;and,whatismore,Imusthaveyouunderstandthatfreshairisnecessary,orelseweshouldbeimperfectinourreasoningandourexperiments.Hereisajarofair;Iplaceitoveracandle,anditburnsverynicelyinitatfirst,showingthatwhatIhavesaidaboutitistrue;buttherewillsoonbeachange.Seehowtheflameisdrawingupward,presentlyfading,andatlastgoingout.Andgoingout,why?Notbecauseitwantsairmerely,forthejarisasfullnowasitwasbefore;butitwantspure,freshair.Thejarisfullofair,partlychanged,partlynotchanged;butitdoesnotcontainsufficientofthefreshairwhichisnecessaryforthecombustionofacandle.Thesea

reallpointswhichwe,asyoungchemists,havetogatherup;andifwelookalittlemorecloselyintothiskindofaction,weshallfindcertainstepsofreasoningextremelyinteresting.Forinstance,hereistheoil-lampIshowedyou-anexcellentlampforourexperiments-theoldArgandlamp.Inowmakeitlikeacandle(obstructingthepassageofairintothecentreoftheflame);thereisthecotton;thereistheoilrisingupinit,andthereistheconicalflame.Itburnspoorlybecausethereisapartialrestraintofair.Ihaveallowednoairtogettoitsavearoundtheoutsideoftheflame,anditdoesnotburnwell.Icannotadmitmoreairfromtheoutside,becausethewickislarge;butif,asArganddidsocleverly,Iopenapassagetothemiddleoftheflame,andsoletaircomeinthere,youwillseehowmuchmorebeautifullyitburns.IfIshuttheairoff,lookhowitsmokes;andwhy?Wehavenowsomeveryinterestingpointstostudy:wehavethecaseofthecombustionofacandle;wehavethecaseofa

candlebeingputoutbythewantofair;andwehavenowthecaseofimperfectcombustion,andthisistoussointerestingthatIwantyoutounderstanditasthoroughlyasyoudothecaseofacandleburninginitsbestpossiblemanner.Iwillnowmakeagreatflame,becauseweneedthelargestpossibleillustrations.Hereisalargerwick(burningturpentineonaballofcotton).Allthesethingsarethesameascandles,afterall.Ifwehavelargerwicks,wemusthavealargersupplyofair,orweshallhavelessperfectcombustion.Look,now,atthisblacksubstancegoingupintotheatmosphere;thereisaregularstreamofit.Ihaveprovidedmeanstocarryofftheimperfectlyburnedpart,lestitshouldannoyyou.Lookatthesootsthatflyofffromtheflame;seewhatanimperfectcombustionitis,becauseitcannotgetenoughair.What,then,ishappening?Why,certainthingswhicharenecessarytothecombustionofacandleareabsent,andverybadresultsareaccordinglyproduced;butweseewhathappenstoaca

ndlewhenitisburntinapureandproperstateofair.AtthetimewhenIshowedyouthischarringbytheringofflameontheonesideofthepaper,Imighthavealsoshownyou,byturningtotheotherside,thattheburningofacandleproducesthesamekindofsoot-charcoal,orcarbon.

But,beforeIshowthat,letmeexplaintoyou,asitisquitenecessaryforourpurpose,that,thoughItakeacandle,andgiveyou,asthegeneralresult,itscombustionintheformofaflame,wemustseewhethercombustionisalwaysinthiscondition,orwhetherthereareotherconditionsofflame;andweshallsoondiscoverthatthereare,andthattheyaremostimportanttous.Ithink,


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perhaps,thebestillustrationofsuchapointtous,asjuveniles,istoshowtheresultofstrongcontrast.Hereisalittlegunpowder.Youknowthatgunpowderburnswithflame;wemayfairlycallitflame.Itcontainscarbonandothermaterials,whichaltogethercauseittoburnwithaflame.Andhereissomepulverizediron,orironfilings.NowIpurposeburningthesetwothingstogether.IhavealittlemortarinwhichIwillmixthem.(BeforeIgointotheseexperiments,letmehopethatnoneofyou,bytryingtorepeatthemforfun'ssake,willdoanyharm.Thesethingsmayallbeveryproperlyusedifyoutakecare,butwithoutthatmuchmischiefwillbedone.)Well,thenhereisalittlegunpowder,whichIputatthebottomofthatlittlewoodenvessel,andmixtheironfilingsupwithit,myobjectbeingtomakethegunpowdersetfiretothefilingsandburnthemintheair,andtherebyshowthedifferencebetweensubstancesburningwithflameandnotwithflame.Hereisthemixture;andwhenIsetfiretoityoumustwatchthecombustion,andyouwillseethatitisoftwokinds.Youwillseethegunpowderburningwithaflameandthefilingsthrownup.Youwillseethemburning,too,butwithouttheproductionofflame.Theywilleachburnseparately.[Thelecturerthenignitedthemixture.]Thereisthegunpowder,whichburnswithaflame,andtherearethefilings:theyburnwithadifferentkindofcombustion.Yousee,then,thesetwogreatdistinctions;anduponthesedifferencesdependalltheutilityandallthebeautyofflamewhichweuseforthepurposeofgivingoutlight.Whenweuseoil,orgas,orcandleforthepurposeofillumination,theirfitnessalldependsuponthesedifferentkindsofcombustion.

Therearesuchcuriousconditionsofflamethatitrequiressomecleverness

andnicetyofdiscriminationtodistinguishthekindsofcombustiononefromanother.Forinstance,hereisapowderwhichisverycombustible,consisting,asyousee,ofseparatelittleparticles.Itiscalledlycopodium,7andeachoftheseparticlescanproduceavapor,andproduceitsownflame;but,toseethemburning,youwouldimagineitwasalloneflame.Iwillnowsetfiretoaquantity,andyouwillseetheeffect.Wesawacloudofflame,apparentlyinonebody;butthatrushingnoise[referringtothesoundproducedbytheburning]wasaproofthatthecombustionwasnotacontinuousorregularone.Thisisthelightningofthepantomimes,andaverygoodimitation.[Theexperimentwastwicerepeatedbyblowinglycopodiumfromaglasstubethroughaspiritflame.]ThisisnotanexampleofcombustionlikethatofthefilingsIhavebeenspeakingof,towhichwemustnowreturn.

[Footnote7:Lycopodiumisayellowishpowderfoundinthefruitoftheclubmoss(Lycopodiumclavatum).Itisusedinfireworks.]

SupposeItakeacandleandexaminethatpartofitwhichappearsbrightesttooureyes.Why,thereIgettheseblackparticles,whichalreadyyouhaveseenmanytimesevolvedfromtheflame,andwhichIamnowabouttoevolveinadifferentway.Iwilltakethiscandleandclearawaythegutterage,whichoccursbyreasonofthecurrentsofair,andifInowarrangetheglasstubesoasjusttodipintothisluminouspart,asinourfirstexperiment,onlyhigher,youseetheresult.Inplaceofhavingthesamewhitevaporthatyouhadbefore,youwillnowhaveablackvapor.Thereisgoes,asblackasink.Itiscertainlyverydifferentfromthewhitevapor;andwhenweputalighttoitweshallfindthatitdoesnotburn,butthatitputsthelightout.Well,theseparticles,asIsa

idbefore,arejustthesmokeofthecandle;andthisbringstomindthatoldemploymentwhichDeanSwiftrecommendedtoservantsfortheiramusement,namelywritingontheceilingofaroomwithacandle.Butwhatisthatblacksubstance?Why,itisthesamecarbonwhichexistsinthecandle.Howcomesitoutofthecandle?Itevidentlyexistedinthecandle,orelseweshouldnothavehadithere.AndnowIwantyoutofollowmeinthisexplanation.YouwouldhardlythinkthatallthosesubstanceswhichflyaboutLondon,intheformofsootsandblacks,aretheverybeautyandlifeoftheflame,andwhichareburnedinitasthoseironfilingswereburnedhere.Hereisapieceofwiregauze,whichwillnotlettheflamegothroughit;andIthinkyouwillsee,almostimmediately,thatwh


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enIbringitlowenoughtotouchthatpartoftheflamewhichisotherwisesobright,itquellsandquinchesitatonce,andallowsavolumeofsmoketoriseup.

Iwantyounowtofollowmeinthispoint-thatwheneverasubstanceburns,astheironfilingsburntintheflameofgunpowder,withoutassumingthevaporousstate(whetheritbecomesliquidorremainssolid),itbecomesexceedinglyluminous.Ihaveheretakenthreeorfourexamplesapartfromthecandleonpurposetoillustratethispointtoyou,becausewhatIhavetosayisapplicabletoallsubstances,whethertheyburnorwhethertheydonotburn-thattheyareexceedinglybrightiftheyretaintheirsolidstate,andthatitistothispresenceofsolidparticlesinthecandleflamethatitowesitsbrilliancy.

Hereisaplatinumwire,abodywhichdoesnotchangebyheat.IfIheatitinthisflame,seehowexceedinglyluminousitbecomes.Iwillmaketheflamedimforthepurposeofgivingalittlelightonly,andyetyouwillseethattheheatwhichitcangivetothatplatinumwire,thoughfarlessthantheheatithasitself,isabletoraisetheplatinumwiretoafarhigherstateofeffulgence.Thisflamehascarboninit;butIwilltakeonethathasnocarboninit.Thereisamaterial,akindoffuel-avapor,orgas,whicheveryouliketocallit-inthatvessel,andithasnosolidparticlesinit;soItakethatbecauseitisanexampleofflameitselfburningwithoutanysolidmatterwhatever;andifInowputthissolidsubstanceinit,youseewhatanintenseheatithas,andhowbrightlyitcausesthesolidbodytoglow.Thisisthepipethroughwhich

weconveythisparticulargas,whichwecallhydrogen,andwhichyoushallknowallaboutthenexttimewemeet.Andhereisasubstancecalledoxygen,bymeansofwhichthishydrogencanburn;andalthoughweproduce,bytheirmixture,fargreaterheat8thanyoucanobtainfromthecandle,yetthereisverylittlelight.If,however,Itakeasolidsubstance,andputthatintoit,weproduceanintenselight.IfItakeapieceoflime,asubstancewhichwillnotburn,andwhichwillnotvaporizebytheheat(andbecauseitdoesnotvaporizeremainssolid,andremainsheated),youwillsoonobservewhathappensastoitsglowing.Ihavehereamostintenseheatproducedbytheburningofhydrogenincontactwiththeoxygen;butthereisasyetverylittlelight-notforwantofheat,butforwantofparticleswhichcanretaintheirsolidstate;butwhenIholdthispieceoflimeintheflameofthehydrogenasitburnsintheoxygen,seehowitglows!Thisisgloriouslimelight,whichrivalsthevoltaiclight,andwhichi

salmostequaltosunlight.Ihavehereapieceofcarbonorcharcoal,whichwillburnandgiveuslightexactlyinthesamemannerasifitwereburntaspartofacandle.Theheatthatisintheflameofacandledecomposesthevaporofthewax,andsetsfreethecarbonparticles;theyriseupheatedandglowingasthisnowglows,andthenenterintotheair.Buttheparticles,whenburnt,neverpassofffromacandleintheformofcarbon.Theygooffintotheairasaperfectlyinvisiblesubstance,aboutwhichweshallknowhereafter.

[Footnote8:Bunsenhascalculatedthatthetemperatureoftheoxyhydrogenblowpipeis8061C.Hydrogenburninginairhasatemperatureof3259C.,andcoalgasinair,2350C]

Isitnotbeautifultothinkthatsuchaprocessisgoingon,andthatsuch

adirtythingsascharcoalcanbecomesoincandescent?Youseeitcomestothis-thatallbrightflamescontainthesesolidparticles;allthingsthatburnandproducesolidparticles,eitherduringthetimetheyareburning,asinthecandle,orimmediatelyafterbeingburnt,asinthecaseofthegunpowderandironfilings-allthesethingsgiveusthisgloriousandbeautifullight.

Iwillgiveyouafewillustrations.Hereisapieceofphosphorus,whichburnswithabrightflame.Verywell;wemaynowconcludethatphosphoruswillproduce,eitheratthemomentthatitisburningorafterwards,thesesolidparticles.Hereisthephosphoruslighted,andIcoveritoverwiththisglassforthe


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purposeofkeepinginwhatisproduced.Whatisallthatsmoke?Thatsmokeconsistsofthoseveryparticleswhichareproducedbythecombustionofthephosphorus.Here,again,aretwosubstances.Thisischlorateofpotassa,andthisothersulphuretofantimony.Ishallmixthesetogetheralittle,andthentheymaybeburntinmanyways.Ishalltouchthemwithadropofsulphuricacid,forthepurposeofgivingyouanillustrationofchemicalaction,andtheywillinstantlyburn.9[Thelecturerthenignitedthemixturebymeansofsulphuricacid.]Now,fromtheappearanceofthings,youcanjudgeforyourselveswhethertheyproducesolidmatterinburning.Ihavegivenyouthetrainofreasoningwhichwillenableyoutosaywhethertheydoordonot;forwhatisthisbrightflamebutthesolidparticlespassingoff?

[Footnote9:Thefollowingistheactionofthesulphuricininflamingthemixtureofsulphuretofantimonyandchlorateofpotassa.Aportionofthelatterisdecomposedbythesulphuricacidintooxideofchlorine,bisulphateofpotassa,andperchlorateofpotassa.Theoxideofchlorineinflamesthesulphuretofantimony,whichisacombustiblebody,andthewholemassinstantlyburstsintoflame.]

Mr.Andersonhasinthefurnaceaveryhotcrucible.Iamabouttothrowintoitsomezincfilings,andtheywillburnwithflamelikegunpowder.Imakethisexperimentbecauseyoucanmakeitwellathome.NowIwantyoutoseewhatwillbetheresultofthecombustionofthiszinc.Hereitisburning-burningbeautifullylikeacandle,Imaysay.Butwhatisallthatsmoke,andwhataretho

selittlecloudsofwoolwhichwillcometoyouifyoucannotcometothem,andmakethemselvessensibletoyouintheformoftheoldphilosophicwool,asitwascalled?Weshallhaveleftinthatcrucible,also,aquantityofthiswoollymatter.ButIwilltakeapieceofthissamezinc,andmakeanexperimentalittlemorecloselyathome,asitwere.Youwillhaveherethesamethinghappening.Hereisthepieceofzinc;there[pointingtoajetofhydrogen]isthefurnace,andwewillsettoworkandtryandburnthemetal.Itglows,yousee;thereisthecombustion;andthereisthewhitesubstanceintowhichitburns.Andso,ifItakethatflameofhydrogenastherepresentativeofacandle,andshowyouasubstancelikezincburningintheflame,youwillseethatitwasmerelyduringtheactionofcombustionthatthissubstanceglowed-whileitwaskepthot;andifItakeaflameofhydrogenandputthiswhitesubstancefromthezincintoit,lookhowbeautifullyitglows,andjustbecauseitisasolidsubstance

.

IwillnowtakesuchaflameasIhadamomentsince,andsetfreefromittheparticlesofcarbon.Hereissomecamphene,whichwillburnwithasmoke;butifIsendtheseparticlesofsmokethroughthispipeintothehydrogenflameyouwillseetheywillburnandbecomeluminous,becauseweheatthemasecondtime.Theretheyare.Thosearetheparticlesofcarbonreignitedasecondtime.Theyarethoseparticleswhichyoucaneasilyseebyholdingapieceofpaperbehindthem,andwhich,whiletheyareintheflame,areignitedbytheheatproduced,and,whensoignited,producethisbrightness.Whentheparticlesarenotseparatedyougetnobrightness.Theflameofcoalgasowesitsbrightnesstotheseparation,duringcombustion,oftheseparticlesofcarbon,whichareequallyinthatasinacandle.Icanveryquicklyalterthatarrangement.Here,forinsta

nceisabrightflameofgas.SupposingIaddsomuchairtotheflameastocauseitalltoburnbeforethoseparticlesaresetfree,Ishallnothavethisbrightness;andIcandothatinthisway:IfIplaceoverthejetthiswire-gauzecap,asyousee,andthenlightthegasoverit,itburnswithanon-luminousflame,owingtoitshavingplentyofairmixedwithitbeforeitburns;andifIraisethegauze,youseeitdoesnotburnbelow10.Thereisplentyofcarboninthegas;but,becausetheatmospherecangettoit,andmixwithitbeforeitburns,youseehowpaleandbluetheflameis.AndifIblowuponabrightgasflame,soastoconsumeallthiscarbonbeforeitgetsheatedtotheglowingpoint,itwillalsoburnblue.[Thelecturerillustratedhisremarksbyblowingonthe


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gaslight.]TheonlyreasonwhyIhavenotthesamebrightlightwhenIthusblowupontheflameisthatthecarbonmeetswithsufficientairtoburnitbeforeitgetsseparatedintheflameinafreestate.Thedifferenceissolelyduetothesolidparticlesnotbeingseparatedbeforethegasisburnt.

[Footnote10:The"air-burner,"whichisofsuchvalueinthelaboratory,owesitsadvantagetothisprinciple.Itconsistsofacylindricalmetalchimney,coveredatthetopwithapieceofrathercoarseironwiregauze.ThisissupportedoveranArgandburnerinsuchamannerthatthegasmaymixinthechimneywithanamountofairsufficienttoburnthecarbonandhydrogensimultaneously,sothattheremaybenoseparationofcarbonintheflamewithconsequentdepositionofsoot.Theflame,beingunabletopassthroughthewiregauze,burnsinasteady,nearlyinvisiblemannerabove.]

Youobservethattherearecertainproductsastheresultofthecombustionofacandle,andthatoftheseproductsoneportionmaybeconsideredascharcoal,orsoot;thatcharcoal,whenafterwardburnt,producessomeotherproduct;anditconcernsusverymuchnowtoascertainwhatthatotherproductis.Weshowedthatsomethingwasgoingaway;andIwantyounowtounderstandhowmuchisgoingupintotheair;andforthatpurposewewillhavecombustiononalittlelargerscale.Fromthatcandleascendsheatedair,andtwoorthreeexperimentswillshowyoutheascendingcurrent;but,inordertogiveyouanotionofthequantityofmatterwhichascendsinthisway,IwillmakeanexperimentbywhichIshalltrytoimprisonsomeoftheproductsofthiscombustion.Forthispurpose

Ihaveherewhatboyscallafire-balloon;Iusethisfire-balloonmerelyasasortofmeasureoftheresultofthecombustionweareconsidering;andIamabouttomakeaflameinsuchaneasyandsimplemannerasshallbestservemypresentpurpose.Thisplateshallbethe"cup,"wewillsosay,ofthecandle;thisspiritshallbeourfuel;andIamabouttoplacethischimneyoverit,becauseitisbetterformetodosothantoletthingsproceedatrandom.Mr.Andersonwillnowlightthefuel,andhereatthetopweshallgettheresultsofthecombustion.Whatwegetatthetopofthattubeisexactlythesame,generallyspeaking,asyougetfromthecombustionofacandle;butwedonotgetaluminousflamehere,becauseweuseasubstancewhichisfeebleincarbon.Iamabouttoputthisballoon-notintoaction,becausethatisnotmyobject-buttoshowyoutheeffectwhichresultsfromtheactionofthoseproductswhicharisefromthecandle,astheyariseherefromthefurnace.[Theballoonwasheldoverthech

imney,whenitimmediatelycommencedtofill.]Youseehowitisdisposedtoascend;butwemustnotletitup;becauseitmightcomeincontactwiththoseuppergaslights,andthatwouldbeveryinconvenient.[Theuppergaslightswereturnedoutattherequestofthelecturer,andtheballoonwasallowedtoascend.]Doesnotthatshowyouwhatalargebulkofmatterisbeingevolved?Nowthereisgoingthroughthistube[placingalargeglasstubeoveracandle]alltheproductsofthatcandle,andyouwillpresentlyseethatthetubewillbecomequiteopaque.SupposeItakeanothercandle,andplaceitunderajar,andthenputalightontheotherside,justtoshowyouwhatisgoingon.Youseethatthesidesofthejarbecomecloudy,andthelightbeginstoburnfeebly.Itistheproducts,yousee,whichmakethelightsodim,andthisisthesamethingwhichmakesthesidesofthejarsoopaque.Ifyougohome,andtakeaspoonthathasbeeninthecoldair,andholditoveracandle-notsoastosootit-youwillf

indthatitbecomesdimjustasthatjarisdim.Ifyoucangetasilverdish,orsomethingofthatkind,youwillmaketheexperimentstillbetter;andnow,justtocarryyourthoughtsforwardtothetimeweshallnextmeet,letmetellyouthatitiswaterwhichcausesthedimness,andwhenwenextmeetIwillshowthatwecanmakeit,withoutdifficulty,assumetheformofaliquid.

LectureIII:Products:WaterFromTheCombustion-NatureOfWater-ACompound-Hydrogen


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lsemaybeused,provideditbeclean,andcancarryofftheheat,andsocondensethewater.

Andnow-togointothehistoryofthiswonderfulproductionofwaterfromcombustibles,andbycombustion-Imustfirstofalltellyouthatthiswatermayexistindifferentconditions;andalthoughyoumaynowbeacquaintedwithallitsforms,theystillrequireustogivealittleattentiontothemforthepresent;sothatwemayperceivehowthewater,whileitgoesthroughitsProteanchanges,isentirelyandabsolutelythesamething,whetheritisproducedfromacandle,bycombustion,orfromtheriversorocean.

Firstofall,water,whenatthecoldest,isice.Nowwephilosophers-IhopethatImayclassyouandmyselftogetherinthiscase-speakofwateraswater,whetheritbeinitssolid,orliquid,orgaseousstate-wespeakofitchemicallyaswater.Waterisathingcompoundedoftwosubstances,oneofwhichwehavederivedfromthecandle,andtheotherweshallfindelsewhere.Watermayoccurasice;andyouhavehadmostexcellentopportunitieslatelyofseeingthis.Icechangesbackintowater-forwehadonourlastSabbathastronginstanceofthischangebythesadcatastrophewhichoccurredinourownhouse,aswellasinthehousesofmanyofourfriends-icechangesbackintowaterwhenthetemperatureisraised;wateralsochangesintosteamwhenitiswarmedenough.Thewaterwhichwehaveherebeforeusisinitsdenseststate11;and,althoughitchangesinweight,incondition,inform,andinmanyotherqualities,itstilliswater;andwhetherwealteritintoicebycooling,orwhetherwechangei

tintosteambyheat,itincreasesinvolumeintheonecaseverystrangelyandpowerfully,andintheothercaseverylargelyandwonderfully.Forinstance,Iwillnowtakethistincylinder,andpouralittlewaterintoit,and,seeinghowmuchwaterIpourin,youmayeasilyestimateforyourselveshowhighitwillriseinthevessel:itwillcoverthebottomabouttwoinches.Iamnowabouttoconvertthewaterintosteamforthepurposeofshowingtoyouthedifferentvolumeswhichwateroccupiesinitsdifferentstatesofwaterandsteam.

[Footnote11:Waterisinitsdenseststateatatemperatureof39.1Fahrenheit.]

Letusnowtakethecaseofwaterchangingintoice:wecaneffectthatbycoolingitinamixtureofsaltandpoundedice12-andIshalldosotoshowyo

utotheexpansionofwaterintoathingoflargerbulkwhenitissochanged.Thesebottles[holdingone]aremadestrongcastiron,verystrongandverythick-Isupposetheyarethethirdofaninchinthickness;theyareverycarefullyfilledwithwater,soastoexcludeallair,andthentheyarescreweddowntight.Weshallseethatwhenwefreezethewaterintheseironvessels,theywillnotbeabletoholdtheice,andtheexpansionwithinthemwillbreaktheminpiecesasthese[pointingtosomefragments]arebroken,whichhavebeenbottlesofexactlythesamekind.Iamabouttoputthesetwobottlesintothatmixtureoficeandsaltforthepurposeofshowingthatwhenwaterbecomesiceitchangesinvolumeinthisextraordinaryway.

[Footnote12:Amixtureofsaltandpoundedicereducesthetemperaturefrom32Fahrenheittozero,theiceatthesametimebecomingfluid.]

Inthemeantime,lookatthechangewhichhastakenplaceinthewatertowhichwehaveappliedheat;itislosingitsfluidstate.Youmaytellthisbytwoorthreecircumstances.Ihavecoveredthemouthofthisglassflask,inwhichwaterisboiling,withawatch-glass.Doyouseewhathappens?Itrattlesawaylikeavalvechattering,becausethesteamrisingfromtheboilingwatersendsthevalveupanddown,andforcesitselfout,andsomakesitclatter.Youcanveryeasilyperceivethattheflaskisquitefullofsteam,orelseitwouldnotforceitswayout.Yousee,also,thattheflaskcontainsasubstanceverymuchlargerthanthewater,foritfillsthewholeoftheflaskoverandoveragain,a


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ndthereitisblowingawayintotheair;andyetyoucannotobserveanygreatdiminutioninthebulkofthewater,whichshowsyouthatitschangeofbulkisverygreatwhenitbecomessteam.

Ihaveputourironbottlescontainingwaterintothisfreezingmixture,thatyoumayseewhathappens.Nocommunicationwilltakeplace,youobserve,betweenthewaterinthebottlesandtheiceintheoutervessel.Buttherewillbeaconveyanceofheatfromtheonetotheother,andifwearesuccessful-wearemakingourexperimentinverygreathaste-Iexpectyouwillby-and-by,sosoonasthecoldhastakenpossessionofthebottlesandtheircontents,hearapopontheoccasionoftheburstingoftheonebottleortheother,and,whenwecometoexaminethebottles,weshallfindtheircontentsmassesofice,partlyinclosedbythecoveringofironwhichistoosmallforthem,becausetheiceislargerinbulkthanthewater.Youknowverywellthaticefloatsuponwater;ifaboyfallsthroughaholeintothewater,hetriestogetontheiceagaintofloathimup.Whydoestheicefloat?Thinkofthat,andphilosophize.Becausetheiceislargerthanthequantityofwaterwhichcanproduceit,andthereforetheiceweighsthelighterandthewateristheheavier.

Toreturnnowtotheactionofheatonwater.Seewhatastreamofvaporisissuingfromthistinvessel!Youobserve,wemusthavemadeitquitefullofsteamtohaveitsentoutinthatgreatquantity.Andnow,aswecanconvertthewaterintosteambyheat,weconvertitbackintoliqui!waterbytheapplicationofcold.Andifwetakeaglass,oranyothercoldthing,andholditoverthis

steam,seehowsoonitgetsdampwithwater:itwillcondenseituntiltheglassiswarm-itcondensesthewaterwhichisnowrunningdownthesidesofit.Ihavehereanotherexperimenttoshowthecondensationofwaterfromavaporousstatebackintoaliquidstate,inthesamewayasthevapor,oneoftheproductsofthecandle,wascondensedagainstthebottomofthedishandobtainedintheformofwater;andtoshowyouhowtrulyandthoroughlythesechangestakeplace,Iwilltakethistinflask,whichisnowfullofsteam,andclosethetop.Weshallseewhattakesplacewhenwecausethiswaterorsteamtoreturnbacktothefluidstatebypouringsomecoldwaterontheoutside.[Thelecturerpouredthecoldwateroverthevessel,whenitimmediatelycollapsed.]Youseewhathashappened.IfIhadclosedthestopper,andstillkepttheheatappliedtoit,itwouldhaveburstthevessel;yet,whenthesteamreturnstothestateofwater,thevesselcollapses,therebeingavacuumproducedinsidebythecondensation

ofthesteam.Ishowyoutheseexperimentsforthepurposeofpointingoutthatinalltheseoccurrencesthereisnothingthatchangesthewaterintoanyotherthing;itstillremainswater;andsothevesselisobligedtogiveway,andiscrushedinward,asintheothercase,bythefartherapplicationofheat,itwouldhavebeenblownoutward.

Andwhatdoyouthinkthebulkofthatwateriswhenitassumesthevaporouscondition?Youseethatcube[pointingtoacubicfoot].There,byitsside,isacubicinch,exactlythesameshapeasthecubicfoot,andthatbulkofwater[thecubicinch]issufficienttoexpandintothatbulk[thecubicfoot]ofsteam;and,onthecontrary,theapplicationofcoldwillcontractthatlargequantityofsteamintothissmallquantityofwater.[Oneoftheironbottlesburstatthatmoment.]Ah!Thereisoneofourbottlesburst,andhere,yousee,isacr

ackdownonesideaneighthofaninchinwidth.[Theothernowexploded,sendingthefreezingmixtureinalldirections.]Thisotherbottleisalsobroken;althoughtheironwasnearlyhalfaninchthick,theicehasburstitasunder.Thesechangesalwaystakeplaceinwater;theydonotrequiretobealwaysproducedbyartificialmeans;weonlyusethemherebecausewewanttoproduceasmallwinterroundthatlittlebottleinsteadofalongandsevereone.ButifyougotoCanada,ortotheNorth,youwillfindthetemperaturethereoutofdoorswilldothesamethingashasbeendoneherebythefreezingmixture.

Toreturntoourquietphilosophy.Weshallnotinfuturebedeceived,there


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fore,byanychangesthatareproducedinwater.Wateristhesameeverywhere,whetherproducedfromtheoceanorfromtheflameofthecandle.Where,then,isthiswaterwhichwegetfromacandle?Imustanticipatealittle,andtellyou.Itevidentlycomes,astopartofit,fromthecandle,butisitwithinthecandlebeforehand?No,itisnotinthecandle;anditisnotintheairaroundaboutthecandlewhichisnecessaryforitscombustion.Itisneitherinonenortheother,butitcomesfromtheirconjointaction,apartfromthecandle,apartfromtheair;andthiswehavenowtotrace,sothatwemayunderstandthoroughlywhatisthechemicalhistoryofacandlewhenwehaveitburningonourtable.Howshallwegetatthis?Imyselfknowplentyofways,butIwantyoutogetatitfromtheassociationinyourownmindsofwhatIhavealreadytoldyou.

Ithinkyoucanseealittleinthisway.WehadjustnowthecaseofasubstancewhichacteduponthewaterinthewaythatSirHumphryDavyshowedus13,andwhichIamnowgoingtorecalltoyourmindsbymakingagainanexperimentuponthatdish.Itisathingwhichwehavetohandleverycarefully;foryousee,ifIallowalittlesplashofwatertocomeuponthismass,itsetsfiretopartofit;andiftherewerefreeaccessofair,itwouldquicklysetfiretothewhole.Nowthisisametal-abeautifulandbrightmetal-whichrapidlychangesintheair,and,asyouknow,rapidlychangesinwater.Iwillputapieceonthewater,andyouseeitburnsbeautifully,makingafloatinglamp,usingthewaterintheplaceofair.Again,ifwetakeafewironfilingsorturningsandputtheminwater,wefindthattheylikewiseundergoanalteration.Theydonotchangesomuchasthispotassiumdoes,buttheychangesomewhatinthesameway

;theybecomerusty,andshowanactionuponthewater,thoughinadifferentdegreeofintensitytowhatthisbeautifulmetaldoes;buttheyactuponthewaterinthesamemannergenerallyasthispotassium.Iwantyoutoputthesedifferentfactstogetherinyourminds.Ihaveanothermetalhere[zinc],andwhenweexamineditwithregardtothesolidsubstanceproducedbyitscombustion,wehadanopportunityofseeingthatitburned;andIsuppose,ifItakealittlestripofthiszincandputitoverthecandle,youwillseesomethinghalfway,asitwere,betweenthecombustionofpotassiumonthewaterandtheactionofiron-youseethereisasortofcombustion.Ithasburned,leavingawhiteashorresiduum;andherealsowefindthatthemetalhasacertainamountofactionuponwater.

[Footnote13:Potassium,themetallicbasisofpotash,wasdiscoveredby

SirHumphryDavyin1807,whosucceededinseparatingitfrompotashbymeansofapowerfulvoltaicbattery.Itsgreataffinityforoxygencausesittodecomposewaterwithevolutionofhydrogen,whichtakesfirewiththeheatproduced.]

Bydegreeswehavelearnedhowtomodifytheactionofthesedifferentsubstances,andtomakethemtelluswhatwewanttoknow.Andnow,firstofall,Itakeiron.Itisacommonthinginallchemicalreactions,wherewegetanyresultofthiskind,tofindthatitisincreasedbytheactionofheat;andifwewanttoexamineminutelyandcarefullytheactionofbodiesoneuponanother,weoftenhavetorefertotheactionofheat.Youareaware,Ibelieve,thatironfilingsburnbeautifullyintheair;butIamabouttoshowyouanexperimentofthiskind,becauseitwillimpressuponyouwhatIamgoingtosayaboutironinitsactiononwater.IfItakeaflameandmakeithollow-youknowwhy,becaus

eIwanttogetairtoitandintoit,andthereforeImakeithollow-andthentakeafewironfilingsanddropthemintotheflame,youseehowwelltheyburn.Thatcombustionresultsfromthechemicalactionwhichisgoingonwhenweignitethoseparticles.Andsoweproceedtoconsiderthesedifferenteffects,andascertainwhatironwilldowhenitmeetswithwater.Itwilltellusthestorysobeautifully,sograduallyandregularly,thatIthinkitwillpleaseyouverymuch.

Ihavehereafurnacewithapipegoingthroughitlikeanirongunbarrel,andIhavestuffedthatbarrelfullofbrightironturnings,andplaceditacros


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sthefiretobemadered-hot.Wecaneithersendairthroughthebarreltocomeincontactwiththeiron,orwecansendsteamfromthislittleboilerattheendofthebarrel.Hereisastop-cockwhichshutsoffthesteamfromthebarreluntilwewishtoadmitit.Thereissomewaterintheseglassjars,whichIhavecoloredblue,sothatyoumayseewhathappens.NowyouknowverywellthatanysteamImightsendthroughthatbarrel,ifitwentthroughintothewater,wouldbecondensed;foryouhaveseenthatsteamcannotretainitsgaseousformifitbecooleddown;yousawithere[pointingtothetinflask]crushingitselfintoasmallbulk,andcausingtheflaskholdingittocollapse;sothatifIweretosendsteamthroughthatbarrelitwouldbecondensed,supposingthebarrelwerecold;itis,therefore,heatedtoperformtheexperimentIamnowabouttoshowyou.Iamgoingtosendthesteamthroughthebarrelinsmallquantities,andyoushalljudgeforyourselves,whenyouseeitissuefromtheotherend,whetheritstillremainssteam.Steamiscondensibleintowater,andwhenyoulowerthetemperatureofsteamyouconvertitbackintofluidwater;butIhaveloweredthetemperatureofthegaswhichIhavecollectedinthisjarbypassingitthroughwaterafterithastraversedtheironbarrel,andstillitdoesnotchangebackintowater.Iwilltakeanothertestandapplytothisgas.(Iholdthejarinaninvertedposition,ormysubstancewouldescape.)IfInowapplyalighttothemouthofthejar,itigniteswithaslightnoise.Thattellsyouthatitisnotsteam;steamputsoutafire;itdoesnotburn;butyousawthatwhatIhadinthatjarburnt.Wemayobtainthissubstanceequallyfromwaterproducedfromthecandleflameasfromanyothersource.Whenitisobtainedbytheactionoftheironupontheaqueousvapor,itleavestheironinastateverysimila

rtothatinwhichthesefilingswereaftertheywereburnt.Itmakestheironheavierthanitwasbefore.Solongastheironremainsinthetubeandisheated,andiscooledagainwithouttheaccessofairorwater,itdoesnotchangeinitsweight;butafterhavinghadthiscurrentofsteampassedoverit,itthencomesoutheavierthanitwasbefore,havingtakensomethingoutofthesteam,andhavingallowedsomethingelsetopassforth,whichweseehere.Andnow,aswehaveanotherjarfull,Iwillshowyousomethingmostinteresting.Itisacombustiblegas;andImightatoncetakethisjarandsetfiretothecontents,andshowyouthatitiscombustible;butIintendtoshowyoumore,ifIcan.Itisalsoaverylightsubstance.Steamwillcondense;thisbodywillriseintheair,andnotcondense.SupposeItakeanotherglassjar,emptyofallbutair:ifIexamineitwithataperIshallfindthatitcontainsnothingbutair.IwillnowtakethisjarfullofthegasthatIamspeakingof,anddealwithitastho

ughitwerealightbody;Iwillholdbothupsidedown,andturntheoneupundertheother;andthatwhichdidcontainthegasprocuredfromthesteam,whatdoesitcontainnow?Youwillfinditnowonlycontainsair.Butlook!Hereisthecombustiblesubstance[takingtheotherjar]whichIhavepouredoutoftheonejarintotheother.Itstillpreservesitsquality,andcondition,andindependence,andthereforeisthemoreworthyofourconsideration,asbelongingtotheproductsofacandle.

Nowthissubstancewhichwehavejustpreparedbytheactionofirononthesteamorwater,wecanalsogetbymeansofthoseotherthingswhichyouhavealreadyseenactsowelluponthewater.IfItakeapieceofpotassium,andmakethenecessaryarrangements,itwillproducethisgas;andif,instead,apieceofzinc,Ifind,whenIcometoexamineitverycarefully,thatthemainreasonw

hythiszinccannotactuponthewatercontinuouslyastheothermetaldoes,isbecausetheresultoftheactionofthewaterenvelopsthezincinakindofprotectingcoat.Wehavelearnedinconsequence,thatifweputintoourvesselonlythezincandwater,they,bythemselves,donotgiverisetomuchaction,andwegetnoresult.ButsupposeIproceedtodissolveoffthisvarnish-thisencumberingsubstance-whichIcandobyalittleacid;themomentIdothisIfindthezincactinguponthewaterexactlyastheirondid,butatthecommontemperature.Theacidinnowayisaltered,exceptinitscombinationwiththeoxideofzincwhichisproduced.Ihavenowpouredtheacidintotheglass,andtheeffectisasthoughIwereapplyingheattocausethisboilingup.Thereissomet


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hingcomingofffromthezincveryabundantly,whichisnotsteam.Thereisajarfullofit;andyouwillfindthatIhaveexactlythesamecombustiblesubstanceremaininginthevessel,whenIholditupsidedown,thatIproducedduringtheexperimentwiththeironbarrel.Thisiswhatwegetfromwater,thesamesubstancewhichiscontainedinthecandle.

Letusnowtracedistinctlytheconnectionbetweenthesetwopoints.Thisishydrogen-abodyclassedamongthosethingswhichinchemistrywecallelements,becausewecangetnothingelseoutofthem.Acandleisnotanelementarybody,becausewecangetcarbonoutofit;wecanbetthishydrogenoutofit,oratleastoutofthewaterwhichitsupplies.Andthisgashasbeensonamedhydrogen,becauseitisthatelementwhich,inassociationwithanothergenerateswater.14Mr.Andersonhavingnowbeenabletogettwoorthreejarsofgas,weshallhaveafewexperimentstomake,andIwanttoshowyouthebestwayofmakingtheseexperiments.Iamnotafraidtoshowyou,forIwishyoutomakeexperiments,ifyouwillonlymakethemwithcareandattention,andtheassentofthosearoundyou.Asweadvanceinchemistryweareobligedtodealwithsubstanceswhichareratherinjuriousifintheirwrongplaces;theacids,andheat,andconbustiblethingsweuse,mightdoharmifcarelesslyemployed.Ifyouwanttomakehydrogen,youcanmakeiteasilyfrombitsofzinc,andsulphuricorpipeintothesudsandblowbubblesbymeansofthehydrogen.YouobservehowthebubblesfalldownwardwhenIblowthemwithmywarmbreath;butnoticethedifferencewhenIblowthemwithhydrogen.[Thelecturerhereblewbubbleswithhydrogen,whichrosetotheroofofthetheatre.]Itshowsyouhowlightthisgasmustbei

nordertocarrywithitnotmerelytheordinarysoapbubble,butthelargerportionofadrophangingtothebottomofit.Icanshowitslightnessinabetterwaythanthis;largerbubblesthanthesemaybesoliftedup;indeed,informertimesballoonsusedtobefilledwiththisgas.Mr.Andersonwillfastenthistubeontoourgenerator,andweshallhaveastreamofhydrogenherewithwhichwecanchargethisballoonmadeofcollodion.Ineednotevenbeverycarefultogetallairout,forIknowthepowerofthisgastocarryitup.[Twocollodionballoonswereinflatedandsentup,onebeingheldbyastring.]Hereisanotherlargerone,madeofthinmembrane,whichwewillfillandallowtoascend;youwillseetheywillallremainfloatingaboutuntilthegasescapes.

[Footnote14:Yowp,"water,"andyevvaw,"Igenerate."]

What,then,arethecomparativeweightsofthesesubstances?Ihaveatableherewhichwillshowyoutheproportionwhichtheirweightsbeartoeachother.Ihavetakenapintandacubicfootasthemeasures,andhaveplacedoppositetothemtherespectivefigures.Apintmeasureofthishydrogenweighsthree-quartersofoursmallestweight,agrain,andacubicfootweighsone-twelfthofanounce;whereasapintofwaterweighs8,750grains,andacubicfootofwaterweighsalmost1,000ounces.Yousee,therefore,whatavastdifferencethereisbetweentheweightofacubicfootofwaterandacubicfootofhydrogen.

Hydrogengivesrisetonosubstancethatcanbecomesolid,eitherduringcombustionorafterwardasaproductofitscombustion;butwhenitburnsitproduceswateronly;andifwetakeacoldglassandputitovertheflame,itbecomesdamp,andyouhavewaterproducedimmediatelyinappreciablequantity;andnoth

ingisproducedbyitscombustionbutthesamewaterwhichyouhaveseentheflameofthecandleproduce.Itisimportanttorememberthatthishydrogenistheonlythinginnaturewhichfurnisheswaterasthesoleproductofcombustion.

Andnowwemustendeavortofindsomeadditionalproofofthegeneralcharacterandcompositionofwater,andforthispurposeIwillkeepyoualittlelonger,sothatatournextmeetingwemaybebetterpreparedforthesubject.Wehavethepowerofarrangingthezincwhichyouhaveseenactinguponthewaterbytheassistanceofanacid,insuchamannerastocauseallthepowertobeevolvedintheplacewherewerequireit.Ihavebehindmeavoltaicpile,andIam


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justabouttoshowyou,attheendofthislecture,itscharacterandpower,thatyoumayseewhatweshallhavetodealwithwhennextwemeet.Iholdheretheextremitiesofthewireswhichtransportthepowerfrombehindme,andwhichIshallcausetoactonthewater.

Wehavepreviouslyseenwhatapowerofcombustionispossessedbythepotassium,orthezinc,ortheironfilings;butnoneofthemshowsuchenergyasthis.[Thelecturerheremadecontactbetweenthetwoterminalwiresofthebattery,whenabrilliantflashoflightwasproduced.]Thislightis,infact,producedbyaforty-zincpowerofburning;itisapowerthatIcancarryaboutinmyhandsthroughthesewiresatpleasure,althoughifIapplieditwronglytomyself,itwoulddestroymeinaninstant,foritisamostintensething,andthepoweryouseehereputforthwhileyoucountfive[bringingthepolesincontactandexhibitingtheelectriclight]isequivalenttothepowerofseveralthunder-storms,sogreatisitsforce15.Andthatyoumayseewhatintenseenergyithas,Iwilltaketheendsofthewireswhichconveythepowerfromthebattery,andwithitIdaresayIcanburnthisironfile.Nowthisisachemicalpower,andonewhich,whenwenextmeet,Ishallapplytowater,andshowyouwhatresultsweareabletoproduce.

[Footnote15:ProfessorFaradayhascalculatedthatthereisasmuchelectricityrequiredtodecomposeonegrainofwaterasthereisinaverypowerfulflashoflightning.]

LectureIV:HydrogenInTheCandle-BurnsIntoWater-TheOtherPartOfWater-Oxygen

Iseeyouarenottiredofthecandleyet,orIamsureyouwouldnotbeinterestedinthesubjectinthewayyouare.Whenourcandlewasburningwefounditproducedwaterexactlylikethewaterwehavearoundus;andbyfartherexaminationofthiswaterwefoundinitthatcuriousbody,hydrogenthatlightsubstanceofwhichthereissomeinthisjar.Weafterwardsawtheburningpowersofthathydrogen,andthatitproducedwater.AndIthinkIintroducedtoyournoticeanapparatuswhichIverybrieflysaidwasanarrangementofchemicalforce,orpower,orenergy,soadjustedastoconveyitspowertousinthesewires;an

dIsaidIshouldusethatforcetopullthewatertopieces,toseewhatelsetherewasinthewaterbesideshydrogen;because,youremember,whenwepassedthewaterthroughtheirontube,webynomeansgottheweightofwaterbackwhichweputinintheformofsteam,thoughwehadaverylargequantityofgasevolved.Wehavenowtoseewhatistheothersubstancepresent.Thatyoumayunderstandthecharacteranduseofthisinstrument,letusmakeanexperimentortwo.Letusputtogether,firstofall,somesubstances,knowingwhattheyare,andthenseewhatthatinstrumentdoestothem.Thereissomecopper(observethevariouschangeswhichitcanundergo),andhereissomenitricacid,andyouwillfindthatthis,beingastrongchemicalagent,willactverypowerfullywhenIaddittothecopper.Itisnowsendingforthabeautifulredvapor;butaswedonotwantthatvapor,Mr.Andersonwillholditnearthechimneyforashorttime,thatwemayhavetheuseandbeautyoftheexperimentwithouttheannoyance.

ThecopperwhichIhaveputintotheflaskwilldissolveit:itwillchangetheacidandthewaterintoabluefluidcontainingcopperandotherthings,andIpurposethenshowingyouhowthisvoltaicbatterydealswithit;andinthemeantimewewillarrangeanotherkindofexperimentforyoutoseewhatpowerithas.Thisisasubstancewhichistouslikewater-thatistosay,itcontainsbodieswhichwedonotknowofasyet,aswatercontainsabodywhichwedonotknowasyet.Nowthissolutionofasalt16Iwillputuponpaper,andspreadabout,andapplythepowerofthebatterytoit,andobservewhatwillhappen.Threeorfourimportantthingswillhappenwhichweshalltakeadvantageof.Iplacethiswettedpaperuponasheetoftinfoil,whichisconvenientforkeepingall


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clean,andalsofortheadvantageousapplicationofthepower;andthissolution,yousee,isnotatallaffectedbybeingputuponthepaperortinfoil,norbyanythingelseIhavebroughtincontactwithityet,andwhich,therefore,isfreetoustouseasregardsthatinstrument.Butfirstletusseethatourinstrumentisinorder.Hereareourwires.Letusseewhetheritisinthestateinwhichitwaslasttime.Wecansoontell.Asyet,whenIbringthemtogether,wehavenopower,becausetheconveyers-whatwecalltheelectrodes-thepassagesorwaysfortheelectricity-arestopped;butnowMr.Andersonbythat[referringtoasuddenflashattheendsofthewires]hasgivenmeatelegramtosaythatitisready.BeforeIbeginourexperimentIwillgetMr.Andersontobreakcontactagainatthebatterybehindme,andwewillputaplatinumwireacrosstoconnectthepoles,andthenifIfindIcanigniteaprettygoodlengthofthiswireweshallbesafeinourexperiment.Nowyouwillseethepower.[Theconnectionwasestablished,andtheintermediatewirebecamered-hot.]Thereisthepowerrunningbeautifullythroughthewire,whichIhavemadethinonpurposetoshowyouthatwehavethosepowerfulforces;andnow,havingthatpower,wewillproceedwithittotheexaminationofwater.

[Footnote16:Asolutionofacetateofleadsubmittedtotheactionofthevoltaiccurrentyieldsleadatthenegativepole,andbrownperoxideofleadatthepositivepole.Asolutionofnitrateofsilver,underthesamecircumstances,yieldssilveratthenegativepole,andperoxideofsilveratthepositive

pole.]

Ihaveheretwopiecesofplatinum,andifIlaythemdownuponthispieceofpaper[themoistenedpaperonthetinfoil]youwillseenoaction;andifItakethemupthereisnochangethatyoucansee,butthearrangementremainsjustasitwasbefore.But,now,seewhathappens:ifItakethesetwopolesandputeitheroneortheotherofthemdownseparatelyontheplatinumplates,theydonothingforme;bothareperfectlywithoutaction;butifIletthembothbeincontactatthesamemoment,seewhathappens[abrownspotappearedundereachpoleofthebattery].Lookhereattheeffectthattakesplace,andseehowIhavepulledsomethingapartfromthewhitesomethingbrown;andIhavenodoubt,ifIweretoarrangeitthus,andweretoputoneofthepolestothetinfoilontheothersideofthepaper-why,Igetsuchabeautifulactionuponthepape

rthatIamgoingtoseewhetherIcannotwritewithit-atelegram,ifyouplease.[Thelecturerheretracedtheword"juvenile"onthepaperwithoneoftheterminalwires.]Seetherehowbeautifullywecangetourresults!

Youseewehaveheredrawnsomethingwhichwehavenotknownaboutbeforeoutofthissolution.LetusnowtakethatflaskfromMr.Anderson'shands,andseewhatwecandrawoutofthat.This,youknow,isaliquidwhichwehavejustmadeupfromcopperandnitricacidwhileourotherexperimentswereinhand;andthoughIammakingthisexperimentveryhastily,andmaybunglealittle,yetIprefertoletyouseewhatIdoratherthanprepareitbeforehand

Nowseewhathappens.Thesetwoplatinumplatesarethetwoends(orIwillmakethemsoimmediately)ofthisapparatus;andIamabouttoputtheminconta

ctwiththatsolution,justaswedidamomentagoonthepaper.Itdoesnotmattertouswhetherthesolutionbeonthepaperorwhetheritbeinthejar,solongaswebringtheendsoftheapparatustoit.IfIputthetwoplatinumsinbythemselvestheycomeoutascleanandaswhiteastheygoin[insertingthemintothefluidwithoutconnectingthemwiththebattery];butwhenwetakethepowerandlaythaton[theplatinumswereconnectedwiththebatteryandagaindippedintothesolution],this,yousee[exhibitingoneoftheplatinums],isatonceturnedintocopper,asitwere;ithasbecomelikeaplateofcopper;andthat[exhibitingtheotherpieceofplatinum]hascomeoutquiteclean.IfItakethiscopperedpieceandchangesides,thecopperwillleavetheright-handside


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andcomeovertotheleftside;whatwasbeforethecopperedplatecomesoutclean,andtheplatewhichwascleancomesoutcoatedwithcopper;andthusyouseethatthesamecopperweputintothissolutionwecanalsotakeoutofitbymeansofthisinstrument.

Puttingthatsolutionaside,letusnowseewhateffectthisinstrumentwillhaveuponwater.HerearetwolittleplatinumplateswhichIintendtomaketheendsofthebattery,andthis(C)isalittlevesselsoshapedastoenablemetotakeittopieces,andshowyouitsconstruction.Inthesetwocups(AandB)Ipourmercury,whichtouchestheendsofthewiresconnectedwiththeplatinumplates.Inthevessel(C)Ipoursomewatercontainingalittleacid(butwhichisputinonlyforthepurposeoffacilitatingtheaction;itundergoesnochangeintheprocess),andconnectedwiththetopofthevesselisabentglasstube(D),whichmayremindyouofthepipewhichwasconnectedwiththegunbarrelinourfurnaceexperiment,andwhichnowpassesunderthejar(F).Ihavenowadjustedthisapparatus,andwewillproceedtoaffectthewaterinsomewayorother.IntheothercaseIsentthewaterthroughatubewhichwasmadered-hot;Iamnowgoingtopasstheelectricitythroughthecontentsofthisvessel.PerhapsImayboilthewater;ifIdoboilthewater,Ishallgetvessel,whichisnowquiteclearandbright,willbecomedim.Therewillbenosound,forthevesselisstrongenoughtoconfinetheexplosion.[Asparkwasthenpassedthroughthejar,whentheexplosivemixturewasignited.]Didyouseethatbrilliantlight?IfIagainscrewthevesselontothejar,andopenthesestop-cocks,youwillseethatthegaswillriseasecondtime.[Thestop-cockswerethenopened.]Th

osegases[referringtothegasesfirstcollectedinthejar,andwhichhadjustbeenignitedbytheelectricspark]havedisappeared,asyousee;theirplaceisvacant,andfreshgashasgonein.Waterhasbeenformedfromthem;andifwerepeatouroperation[repeatingthelastexperiment],Ishallhaveanothervacancy,asyouwillseebythewaterrising.Ialwayshaveanemptyvesselaftertheexplosion,becausethevapororgasintowhichthatwaterhasbeenresolvedbythebatteryexplodesundertheinfluenceofthespark,andchangesintowater;andby-and-byyouwillseeinthisuppervesselsomedropsofwatertricklingdownthesidesandcollectingatthebottom.

Weareheredealingwithwaterentirely,withoutreferencetotheatmosphere.Thewaterofthecandlehadtheatmospherehelpingtoproduceit;butinthiswayitcanbeproducedindependentlyoftheair.Water,therefore,oughttocont

ainthatothersubstancewhichthecandletakesfromtheair,andwhich,combiningwiththehydrogen,produceswater.

Justnowyousawthatoneendofthisbatterytookholdofthecopper,extractingitfromthevesselwhichcontainedthebluesolution.Itwaseffectedbythiswire;andsurelywemaysay,ifthebatteryhassuchpowerwithametallicsolutionwhichwemadeandunmade,maywenotfindthatitispossibletosplitasunderthecomponentpartsofthewater,andputthemintothisplaceandthatplace?SupposeItakethepoles-themetallicendsofthisbattery-andseewhatwillhappenwiththewaterinthisapparatus,wherewehaveseparatedthetwoendsfarapart.Iplaceonehere(atA),andtheotherthere(atB);andIhavelittleshelveswithholeswhichIcanputuponeachpole,andsoarrangethemthatwhateverescapesfromthetwoendsofthebatterywillappearasseparategas

es;foryousawthatthewaterdidnotbecomevaporous,butgaseous.Thewiresarenowinperfectandproperconnectionwiththevesselcontainingthewater,andyouseethebubblesrising;letuscollectthesebubblesandseewhattheyare.Hereisaglasscylinder(O);Ifillitwithwaterandputitoveroneend(A)ofthepile,andIwilltakeanother(H),andputitovertheotherend(B)ofthepile.Andsonowwehaveadoubleapparatus,withbothplacesdeliveringgas.Boththesejarswillfillwithgas.Theretheygo,thattotheright(H)fillingveryrapidly;theonetotheleft(O)fillingnotsorapidly;and,thoughIhaveallowedsomebubblestoescape,yetstilltheactionisgoingonprettyregularly;andwereitnotthatoneisrathersmallerthantheother,youwouldsee


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thatIshouldhavetwiceasmuchinthis(H)asIhaveinthat(O).Boththesegasesarecolorless;theystandoverthewaterwithoutcondensing;theyarealikeinallthings-Imeaninallapparentthings;andwehavehereanopportunityofexaminingthesebodiesandascertainingwhattheyare.Theirbulkislarge,andwecaneasilyapplyexperimentstothem.Iwilltakethisjar(H)first,andwillaskyoutobepreparedtorecognizehydrogen.

Thinkofallitsqualities-thelightgaswhichstoodwellininvertedvessels,burningwithapaleflameatthemouthofthejar,andseewhetherthisgasdoesnotsatisfyalltheseconditions.IfitbehydrogenitwillremainherewhileIholdthisjarinverted.[Alightwasthenapplied,whenthehydrogenburnt.]Whatistherenowintheotherjar?Youknowthatthetwotogethermadeanexplosivemixture.Butwhatcanthisbewhichwefindastheotherconstituentinwater,andwhichmustthereforebethatsubstancewhichmadethehydrogenburn?Weknowthatthewaterweputintothevesselconsistedofthetwothingstogether.Wefindoneoftheseishydrogen:whatmustthatotherbewhichwasinthewaterbeforetheexperiment,andwhichwenowhavebyitself?Iamabouttoputthislightedsplinterofwoodintothegas.Thegasitselfwillnotburn,butitwillmakethesplinterofwoodburn.[Thelecturerignitedtheendofthewoodandintroduceditintothejarofgas.]Seehowitinvigoratesthecombustionofthewood,andhowitmakesitburnfarbetterthantheairwouldmakeitburn;andnowyouseebyitselfthateveryothersubstancewhichiscontainedinthewater,andwhich,whenthewaterwasformedbytheburningofthecandle,musthavebeentakenfromtheatmosphere.Whatshallwecallit,A,B,orC?Letuscall

itO-callit"Oxygen";itisaverygood,distinct-soundingname.This,then,istheoxygenwhichwaspresentinthewater,formingsolargeapartofit.

Weshallnowbegintounderstandmoreclearlyourexperimentsandresearches,becausewhenwehaveexaminedthesethingsonceortwiceweshallsoonseewhyacandleburnsintheair.Whenwehaveinthiswayanalyzedthewater-thatistosay,separatedorelectrolyzeditspartsoutofit,wegettwovolumesofhydrogenandoneofthebodythatburnsit.Andthesetwoarerepresentedtousonthefollowingdiagram,withtheirweightsalsostated;andweshallfindthattheoxygenisaveryheavybodybycomparisonwiththehydrogen.Itistheotherelementinwater.

[Table1]

Ihadbetter,perhaps,tellyounowhowwegetthisoxygenabundantly,havingshownyouhowwecanseparateitfromthewater.Oxygen,asyouwillimmediatelyimagine,existsintheatmosphere;forhowshouldthecandleburntoproducewaterwithoutit?Suchathingwouldbeabsolutelyimpossible,andchemicallyimpossible,withoutoxygen.Canwegetitfromtheair?Well,therearesomeverycomplicatedanddifficultprocessesbywhichwecangetitfromtheair;butwehavebetterprocesses.Thereisasubstancecalledtheblackoxideofmanganese;itisaveryblack-lookingmineral,butveryuseful,andwhenmadered-hotitgivesoutoxygen.Hereisanironbottlewhichhashadsomeofthissubstanceputintoit,andthereisatubefixedtoit,andafirereadymade,andMr.Andersonwillputthatretortintothefire,foritismadeofiron,andcanstandtheheat.Hereisasaltcalledchlorateofpotassa,whichisnowmadeinlargequa

ntitiesforbleaching,andchemicalandmedicaluses,andforpyrotechnicandotherpurposes.Iwilltakesomeandmixitwithsomeoftheoxideofmanganese(oxideofcopper,oroxideofironwoulddoaswell);andifIputthesetogetherinaretort,farlessthanaredheatissufficienttoevolvethisoxygenfromthemixture.Iamnotpreparingtomakemuch,becauseweonlywantsufficientforourexperiments;only,asyouwillseeimmediately,ifIusetoosmallacharge,thefirstportionofthegaswillbemixedwiththeairalreadyintheretort,andIshouldbeobligedtosacrificethefirstportionofthegasbecauseitwouldbesomuchdilutedwithair;thefirstportionmustthereforebethrownaway.Youwillfindinthiscasethatacommonspiritlampisquitesufficientform


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etogettheoxygen,andsoweshallhavetwoprocessesgoingonforitspreparation.Seehowfreelythegasiscomingoverfromthatsmallportionofthemixture.Wewillexamineitandseewhatareitsproperties.Nowinthiswayweareproducing,asyouwillobserve,agasjustliketheonewehadintheexperimentwiththebattery,transparent,undissolvedbywater,andpresentingtheordinaryvisiblepropertiesoftheatmosphere.(Asthisfirstjarcontainstheair,togetherwiththefirstportionsoftheoxygensetfreeduringthepreparation,wewillcarryitoutoftheway,andbepreparedtomakeourexperimentsinaregular,dignifiedmanner.)Andinasmuchasthatpowerofmakingwood,wax,orotherthingsburn,wassomarkedintheoxygenweobtainedbymeansofthevoltaicbatteryfromwater,wemayexpecttofindthesamepropertyhere.Wewilltryit.Youseethereisthecombustionofalightedtaperinair,andhereisitscombustioninthisgas[loweringthetaperintothejar].Seehowbrightlyandhowbeautifullyitburns!Youcanalsoseemorethanthis:youwillperceiveitisaheavygas,whilethehydrogenwouldgouplikeaballoon,orevenfasterthanaballoon,whennotencumberedwiththeweightoftheenvelope.Youmayeasilyseethatalthoughweobtainedfromwatertwiceasmuchinvolumeofthehydrogenasofoxygen,itdoesnotfollowthatwehavetwiceasmuchinweight,becauseoneisheavyandtheotheraverylightgas.Wehavemeansofweighinggasesorair;but,withoutstoppingtoexplainthat,letmejusttellyouwhattheirrespectiveweightsare.Theweightofapintofhydrogenisthree-quartersofagrain;theweightofthesamequantityofoxygenisnearlytwelvegrains.Thisisaverygreatdifference.Theweightofacubicfootofhydrogenisone-twelfthofanounce;andtheweightofacubicfootofoxygenisoneounceandathird.Andsoon

wemightcometomassesofmatterwhichmaybeweighedinthebalance,andwhichwecantakeaccountofastohundred-weightsandastotons,asyouwillseealmostimmediately.

Now,asregardsthisverypropertyofoxygensupportingcombustion,whichwemaycomparetoair,Iwilltakeapieceofcandletoshowityouinaroughway-andtheresultwillberough.Thereisourcandleburningintheair:howwillitburninoxygen?Ihavehereajarofthisgas,andIamabouttoputitoverthecandleforyoutocomparetheactionofthisgaswiththatoftheair.Why,lookatit;itlookssomethinglikethelightyousawatthepolesofthevoltaicbattery.Thinkhowvigorousthatactionmustbe.Andyet,duringallthataction,nothingmoreisproducedthanwhatisproducedbytheburningofthecandleinair.Wehavethesameproductionofwater,andthesamephenomenaexactly,

whenweusethisgasinsteadofair,aswehavewhenthecandleisburntinair.

Butnowwehavegotaknowledgeofthisnewsubstance,wecanlookatitalittlemoredistinctly,inordertosatisfyourselvesthatwehavegotagoodgeneralunderstandingofthispartoftheproductofacandle.Itiswonderfulhowgreatthesupportingpowersofthissubstanceareasregardscombustion.Forinstance,hereisalampwhich,simplethoughitbe,istheoriginal,Imaysay,ofagreatvarietyoflampswhichareconstructedfordiverspurposes-forlighthouses,microscopicilluminations,andotheruses;andifitwasproposedtomakeitburnverybrightly,youwouldsay,"Ifacandleburntbetterinoxygen,willnotalampdothesame?"Why,itwilldoso.Mr.Andersonwillgivemeatubecomingfromouroxygenreservoir,andIamabouttoapplyittothisflame,whichIwillpreviouslymakeburnbadlyonpurpose.Therecomestheoxygen:whataco

mbustionthatmakes!ButifIshutitoff,whatbecomesofthelamp?[Theflowofoxygenwasstopped,andthelamprelapsedtoitsformerdimness.]Itiswonderfulhow,bymeansofoxygen,wegetcombustionaccelerated.Butitdoesnotaffectmerelythecombustionofhydrogen,orcarbon,orthecandle,butitexaltsallcombustionsofthecommonkind.Wewilltakeonewhichrelatestoiron,forinstance,asyouhavealreadyseenironburnalittleintheatmosphere.Hereisajarofoxygen,andthisisapieceorironwire;butifitwereabarasthickasmywrist,itwouldburnthesame.Ifirstattachalittlepieceofwoodtotheiron;Ithensetthewoodonfire,andletthembothdowntogetherintothejar.Thewoodisnowalight,andthereitburnsaswoodshouldburninoxygen;but


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itwillsooncommunicateitscombustiontotheiron.Theironisnowburningbrilliantly,andwillcontinuesoforalongtime.Aslongaswesupplyoxygen,solongwecancarryonthecombustionoftheiron,untilthelatterisconsumed.

Wewillnowputthatononeside,andtakesomeothersubstance;butwemustlimitourexperiments,forwehavenottimetospareforalltheillustrationsyouwouldhavearighttoifwehadmoretime.Wewilltakeapieceofsulphur:youknowhowsulphurburnsintheair;well,weputitintotheoxygen,andyouwillseethatwhatevercanburninaircanburnwithafargreaterintensityinoxygen,leadingyoutothinkthatperhapstheatmosphereitselfowesallitspowerofcombustiontothisgas.Thesulphurisnowburningveryquietlyintheoxygen;butyoucannotforamomentmistaketheveryhighandincreasedactionwhichtakesplacewhenitissoburnt,insteadofbeingburntmerelyincommonair.

Iamnowabouttoshowyouthecombustionofanothersubstancephosphorus.Icandoitbetterforyouherethanyoucandoitathome.Thisisaverycombustiblesubstance;andifitbesocombustibleinair,whatmightyouexpectitwouldbeinoxygen?Iamabouttoshowittoyounotinitsfullestintensity,forifIdidsoweshouldalmostblowtheapparatusup;Imayevennowcrackthejar,thoughIdonotwanttobreakthingscarelessly.Youseehowitburnsintheair.ButwhatagloriouslightitgivesoutwhenIintroduceitintooxygen![Introducingthelightedphosphorusintothejarofoxygen.]Thereyouseethesolidparticlesgoingoffwhichcausethecombustiontobesobrilliantlyluminous.

Thusfarwehavetestedthispowerofoxygen,andthehighcombustionitproduces,bymeansofothersubstances.Wemustnow,foralittlewhilelonger,lookatitasrespectsthehydrogen.Youknow,whenweallowedtheoxygenandthehydrogenderivedfromthewatertomixandburntogether,wehadalittleexplosion.YourememberalsothatwhenIburnttheoxygenandthehydrogeninajettogether,wegotverylittlelight,butgreatheat;Iamnowabouttosetfiretooxygenandhydrogenmixedintheproportioninwhichtheyoccurinwater.Hereisavesselcontainingonevolumeofoxygenandtwovolumesofhydrogen.Thismixtureisexactlyofthesamenatureasthegaswejustnowobtainedfromthevoltaicbattery;itwouldbefartoomuchtoburnatonce;Ihavethereforearrangedtoblowsoapbubbleswithitandburnthosebubbles,thatwemayseebyageneralexperimentortwohowthisoxygensupportsthecombustionofthehydrogen.Firstofall,wewillseewhetherwecanblowabubble.Well,theregoesthegas[c

ausingittoissuethroughatobacco-pipeintosomesoapsuds].HereIhaveabubble.Iamreceivingthemonmyhand,andyouwillperhapsthinkIamactingoddlyinthisexperiment,butitistoshowyouthatwemustnotalwaystrusttonoiseandsounds,butrathertorealfacts.[Explodingabubbleonthepalmofhishand.]Iamafraidtofireabubblefromtheendofthepipe,becausetheexplosionwouldpassupintothejarandblowittopieces.Thisoxygenthen,willunitewiththehydrogen,asyouseebythephenomena,andhearbythesound,withtheutmostreadinessofaction,andallitspowerstothentakenupinitsneutralizationofthequalitiesofthehydrogen.

SonowIthinkyouwillperceivethewholehistoryofwaterwithreferencetooxygenandtheairfromwhatwehavebeforesaid.Whydoesapieceofpotassiumdecomposewater?Becauseitfindsoxygeninthewater.WhatissetfreewhenI

putitinthewater,asIamabouttodoagain?Itsetsfreehydrogen,andthehydrogenburns;butthepotassiumitselfcombineswithoxygen;andthispieceofpotassium,intakingthewaterapart-thewater,youmaysay,derivedfromthe

chemical history of a candle, 1860 michael faraday

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