1. ANTOINE LAVOISIER
Lived1743– 1794.
AntoineLavoisierrevolutionizedchemistry. Henamed
theelementscarbon,hydrogenandoxygen;discovered
oxygen’sroleincombustionandrespiration;
establishedthatwateris a compoundof hydrogenand
oxygen;discoveredthatsulfuris anelement,and
helpedcontinuethetransformationofchemistryfroma
qualitativescienceintoa quantitativeone.
2. Beginnings
Antoine-LaurentLavoisierwas bornintoa privileged
familyonAugust26, 1743inFrance’scapitalcity,Paris.
His fatherwasJean-AntoineLavoisier,a lawyerinthe
ParisParliament.
His motherwasÉmiliePunctis,whosefamilywealth
hadcomefroma butcherybusiness. Shediedwhen
Antoinewasfiveyearsold, leavinghima largeamount
of money.
Betweentheagesof 11 and18, Antoinewaseducated
at CollègedesQuatre-Nations,a collegeofthe
Universityof Paris.Hestudiedgeneral subjects there,
includingthesciencesinhisfinaltwoyears.
Althoughhewas veryattractedtothesciences,he
enrolledinthecollege’slaw schoolat18, aimingto
pursuethesamecareeras hisfather.(Hisfatherhad
encouragedhimto believethatsciencewasmerelya
hobby, nota seriousprofession.)
Aftertwoyearsstudyinglaw,hewasawardeda
bachelor’sdegree.A yearlater,in1764,heobtaineda
licenseto practiceas a lawyer,butdecidedagainstthis.
3. Antoine Lavoisier’s Science
Whilestudyingforhislaw degreeLavoisierhad
maintainedhisinterestinscience, attendingscience
lectures inadditiontolaw lectures.
In 1764, theyearheobtainedhislicense
to practicelaw,healsopublishedhisfirstscientific
paper.Inthesameyearhereada papertotheelite
FrenchAcademyof Sciences.Hewaselectedto the
FrenchAcademyof Sciencesin1769,agedjust26.
Forms of Carbon
In1772Lavoisierandotherchemists boughta
diamondandplaceditina closedglassjar.Theyuseda
remarkablegiantmagnifyingglassto focus thesun’s
raysonthediamond. Thediamondburnedand
disappeared.
Lavoisier’s remarkable combustion apparatus
4. Lavoisiernotedtheoverallweightof thejarwas
unchanged,eventhoughallofthediamondhad
disappeared.Thisobservationwouldlaterbepartof
theevidenceconvincinghimthathislaw of mass
conservationwas correct.
Whetherdiamondor charcoal wereburnedby thegiant
lens,thesamegas wasproduced– wenowcall it
carbondioxide.Lavoisierrealizedthatdiamondand
charcoalaredifferentformsofthesameelement.
He gavethiselementthenamecarbon.
Oxygen and Combustion
In 1772peopledidnotunderstandtheprocessof
burning.Theyhadinconsistent, confusedtheories, chief
of which was thetheoryof phlogiston,anundetectable
substancewhich sometimeshad negativemass!
We nowknow thatcombustionhappenswhen
substancesreactwithoxygenat hightemperatures.In
1772,however, whenLavoisierbeganworkinginthis
field,oxygen’sdiscoveryby JosephPriestleystilllay
twoyears inthefuture.
Lavoisier’sworkenjoyeda greatadvantageovermany
otherscientists – hisgreatpassionforaccurate
5. measurements– quantitativeratherthanqualitative
science.
In 1772Lavoisierdiscoveredthatwhenphosphorusor
sulfurareburnedinairtheproductsareacidic. The
productsalsoweighmorethantheoriginalphosphorus
or sulfur,suggestingtheelements combinewith
somethingintheairto produceacids.Butwhat?
In 1774Joseph PriestleyvisitedParis.HetoldLavoisier
aboutthegas producedwhenhedecomposedthe
compoundwenow calledmercuryoxide. Thisgas
supportedcombustionmuchmorepowerfullythan
normalair.Priestleybelievedthegas wasa particularly
pureversionof air. Hestartedcallingit
dephlogisticatedair,believingits unusual properties
werecausedby theabsenceofphlogiston.
Lavoisierdidnotbelieveitwas dephlogisticated
anything,becausehedidnotbelieveinphlogiston.
In 1779Lavoisiercoinedthenameoxygenforthe
elementreleasedby mercuryoxide.Hefoundoxygen
madeup20 percentof airandwasvitalforcombustion
andrespiration.Healsoconcludedthatwhen
phosphorus orsulfurareburnedinair,theproducts
areformedby thereactionof theseelements with
oxygen.
Antoine Lavoisier
6. Elementary Treatise on Chemistry
“Sulfur,whenburning,absorbs oxygengas;
theresultingacidis considerablyheavierthanthe
sulfurburned;itsweightis equalto thesumof weights
of thesulfurburnedandtheoxygenabsorbed.”
Sulfuris anelement
In 1777Lavoisiercorrectlyidentifiedsulfuras an
element.Hehadcarriedoutextensiveexperiments
involvingthis substanceandobservedthatitcouldnot
be brokendownintoanysimplersubstances.
TheConservationof Mass
In 1778Lavoisierfoundthatwhenmercuryoxideis
heateditsweightdecreases.Theoxygengasitreleases
has exactlythesameweightas theweightlostby the
mercuryoxide.
Whilethismay seemobviousto us today, itwas lessso
in thosedays(hencethegeneralsupportforthe
phlogistontheory).Aftercarryingoutworkwitha
numberofdifferentsubstances,andrecallingearlier
worksuchas hisworkin1772 withcarbon,Lavoisier
7. announceda new fundamentallaw ofnature:thelaw of
conservationofmass:
matteris conservedinchemicalreactions
or statedinanotherway:
thetotalmassof a chemicalreaction’sproductsis
identicaltothetotalmassof thestartingmaterials
It is oftensaidthatLavoisierwasthefirstscientistto
statetheprincipleofmassconservation. Thisis not
strictlyincorrect.In1630 JeanReyhadformulateda
similarlaw;in1755JosephBlackhadassumedthelaw
was trueinhisworkdiscoveringmagnesium;andin
1760MikhailLomonosovhadpublisheda statementof
thelaw.
Thelaw ofmassconservationonlybecamefirmly
establishedafterLavoisierindependentlydiscoveredit.
“In performing experiments, it is necessary… that
they be simplified as much as possible, and that every
circumstancethat could complicate theresults should be
completely removed.”
Combustion and respiration
8. Lavoisiersuspectedthatcombustionandrespiration
arechemically thesame.Hedemonstratedthis withthe
helpofPierre-SimonLaplace. Thepairmeasuredthe
amountof carbondioxideandheatgivenoffby a guinea
pigas itbreathed.They comparedthis totheamountof
heatproducedwhenthey burnedcarbontoproduce
thesameamountofcarbondioxideas hadbeenexhaled
by theguineapig.
TheirresultsallowedLavoisierto concludethat
respirationis a formof combustion. Theheatproduced
by mammals duringrespirationkeeps theirbodies
aboveroomtemperature.
Lavoisier measures the oxygen in air exhaled from a man’s lungs. Lavoisier’s wife Marie-Anne makes notes.A
skilled artist, she also created the engraving from which this image was taken.
Wateris not an element
In 1783Lavoisiercoinedthename‘hydrogen’forthe
gas which HenryCavendishhadrecognizedas a new
elementin1766;Cavendishhadcalledthegas
inflammableair.
9. WorkingagainwithPierre-SimonLaplace,Lavoisier
burnedhydrogenwithoxygenandfoundthatwater
was produced, establishingthatwateris notan
element,butis actuallya compoundmadefromthe
elementshydrogenandoxygen. Thisresultastonished
manypeople,becauseatthattime‘everyoneknew’that
waterwas itselfoneofthe‘indivisible’elements.
Hydrogen means water former in Greek.
“It required85partsby weightof oxygenand15partsof
hydrogento compose100partsof water.”
The Metric System
Starting in 1791, Lavoisierserved on the committee of
the French Academy of Sciences which developedthe
metric system of measurement. Other members of the
committee including the well-knownmathematicians
Pierre-SimonLaplaceand Adrien-MarieLegendre.
Some Personal Details and The End
10. In additiontohisscientificresearch,Lavoisierwas
industrious inotherfields.Attheageof 26 hebought
intoa companywhichgathered taxfortheFrench
government. Havingdonethis, hetriedtoreformtax
law to helppoorertaxpayers. Healsoservedonthe
government’sgunpowdercommission, improvingthe
qualityof French gunpowderconsiderably.Lavoisier
marriedMarie-AnnePierrettePaulzein1771. Hewas
28 andshewasjust13.InmarryingMarie-Anneso
young,hewas actingat therequestofherfather, who
was a seniormemberof thetaxcompanyLavoisierhad
boughtinto. TheCountd’Amerval, whowasabout40,
hadmade
a
proposal
of
marriage
to Marie-
Anneand
her
father
hadbeenthreatenedwith dismissalfromthetax
companyifshedidnotsayyes.Lavoisiersteppedinand
marriedhertoprovideMarie-Anneandherfatherwith
a suitableexcuseforhernotmarryingTheCount.
Marie-Annewasa skilledartistandwell-educated. She
helpedLavoisierconsiderablywith his work,
11. translatingscientificpapers fromEnglishintoFrench –
addingherownnotesandscientific criticisms of
papers,helpingwithlaboratory work,makingaccurate
drawingsof laboratoryapparatusforLavoisier’s
scientificpublications,andkeepingaccuratewritten
records ofLavoisier’sexperiments.
DuringtheFrenchRevolution, which beganin1789,
wealthypeopleandanyonewhohadworkedforthe
governmentwereunderthreat.In1793 the
revolutionariesputan endto theFrench Academyof
Sciencesandotheracademic societies.
In 1794Lavoisierwasbrandeda traitorbecauseofhis
involvementwith taxation. Hewasalsounpopularwith
revolutionariesbecausehehadsupportedforeign
scientists,whomtherevolutionarieswishedto stripof
theirassets.
Lavoisierwassentencedtodeath by the
revolutionaries.Trumped-upchargesagainsthim
includedstealingmoneyfromFrance’sTreasuryand
givingitto France’senemies.
AntoineLavoisierdiedby theguillotineattheageof 50
on May 8, 1794inParis. Marie-Anne’s fatherand26
otherpeoplewereexecutedonthesameoccasion.
12. At theendof1795,ina U-turn,theFrenchgovernment
foundLavoisierinnocentofallcharges. By then,of
course,itwastoolate:hewasjustanotherinnocent
victimof therevolution’sReignofTerror.
Lavoisier’swifeandhistremendouscontributionsto
chemistrysurvived. Ironicallyhiswife,Marie-Anne,
latermarriedBenjaminThompson, whoplayeda key
roleinestablishingthatcaloric, likephlogiston, was
merelya figmentof people’simaginations.
