Precision Instruments and the Demonstrative Order of Proof in Lavoisier's Chemistry
Author(s): Jan Golinski
Reviewed work(s):
Source: Osiris, 2nd Series, Vol. 9, Instruments (1994), pp. 30-47
Published by: The University of Chicago Press on behalf of The History of Science Society
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Precision
Demonstrative Order
in
the
and
Instruments
of
Proof
Chemistry
Lavoisier's
By Jan Golinski*
If it is true that a controversy approaches its conclusion by the
accumulation of facts that impinge upon it, it is only so provided these "facts" are without ambiguity in their implications.
For otherwise, twisted by the rival hypotheses, and sometimes
with so many more words that they convey less sense, these
"facts" so multiply the extraneous questions that controversies
become endless. Thus prejudice and imagination freely hold
sway and logic is replaced by fashion.
-Jean-Andr6 Deluc (1790)1
I
AFTERMORETHAN A DECADE OF DEBATEaboutthe fundamenHAT,
tals of chemical theory,Jean-AndreDeluc should express frustrationis not
reallysurprising.As an upholderof the traditionaltheoryof phlogistonandan opponent of the new theoryof Antoine-LaurentLavoisier,Deluc fearedthatthe controversy wouldneverend. Each new fact could be interpretedin differentways by the
two sides and, ratherthanresolvingthe debate,seemed to bringever more subjects
into doubt.Reason,supposedlythe securepathto scientifictruth,seemed incapable
of decidingthe issue. The same sentimentwas voiced nearlysimultaneouslyby the
EnglishchemistJamesKeir,who triedto curbthe hopes of his fellow phlogistonist
JosephPriestley,who looked forwardto an imminentcompromise.Keir cautioned
that"thereare wonderfulresourcesin the disputeaboutphlogiston,by which either
party can evade, so that I am less sanguinethan you are in my hopes of seeing
it terminated."2
Historiansareinterestedin controversiesfor muchthe samereasonsthathistorical
participantslike Deluc and Keir found them so frustrating.As "facts"accumulate
on each side, less and less appearsto be certain.Instead,debateramifiesacross an
ever wider range of questions.Phenomena,methods, apparatus,personalcompetence, assumptionsandprinciples-all maybecome issues in dispute.Hence if controversiesbecomeprolonged,moreandmorebackgroundassumptionsandpractices
* Departmentof History,Universityof New Hampshire,Durham,New Hampshire03824-3586.
sur la naturede 1eau, du phlogistique,des acides &
l "Lettrede M. DeLuc a M. De La MWtherie,
sur la Physique,sur 1'HistoireNaturelle, et sur les Arts et Medes airs,"Observationset MWmoires
tiers, 1790, 36:144-154, on p. 153.
2 James Keir to Joseph Priestley,[n.d., 1789?], in A ScientificAutobiographyof Joseph Priestley
(1733-1804), ed. RobertE. Schofield(Cambridge,Mass.:MIT Press, 1966), pp. 252-253, on p. 253.
?
1994 by The Historyof Science Society. All rightsreserved.0369-7827/94/0008-0001$01.00
OSIRIS1994, 9: 30-47
30
PROOF IN LAVOISIER'SCHEMISTRY
31
are exposed to view. Much recenthistoricalworkhas shown the value of disputes
as sites for examiningscientific practiceas a social activity.In controversiesit is
particularlyclearhow manyelementsof historicalcontextshaperivalinterpretations
of natureandhow many"wonderfulresources"areavailableto those tryingto close
the issue3
Lavoisier's"chemicalrevolution"presents itself as an underexploitedfield for
such study.Therehas been relativelylittle workon the dynamicsof the controversy,
which ebbed and flowed throughoutthe 1780s and into the following decade. Perhaps historianshave been too concernedwith trying to grasp in essentialistterms
the real natureof Lavoisier'sachievementor assessingwhetherit deservesthe label
"revolution."
The processof persuasionundertakenby Lavoisierandhis allies in the
1780s tends to be regardedas an aftermathto the main events. And yet what Carl
Perrincalled the "'triumph
of the antiphlogistians"was no walkover,but a lengthy
process that deservesdetailedinvestigation.Controversyrangedover numerousissues of fact andswelled to embracemethodological,linguistic,andsocial questions.
Lavoisier'ssystemas a whole was articulatedin the contextof this debate.The mapping of the strugglein its temporal,geographical,and social dimensionsis a largescale task, but one that promisesconsiderablerewardsin historicalunderstanding
of the processesof science.4
Such a mappingcannotbe attemptedhere, thougha step can be takentowardsit
by surveyingthe role of instrumentsin the controversy.TrevorLeverehas recently
remindedus of the importanceof Lavoisier'snovel instruments,includingthe calorimeterand the balance,and of theirrole in the campaignagainstphlogiston.Frederic L. Holmes has pointedout how radicala breakthis apparatusmarkedwith the
"longueduree"of the eighteenth-centurychemicallaboratory.And ArthurDonovan
has arguedthatLavoisier'sinstrumentation
signalshis transferinto chemistryof the
methods of the more mathematizedphysical sciences.5In this articleI build upon
this work to place Lavoisier'sapparatusagainstthe backgroundof the controversy
surroundinghis new chemistry.My aim is to use the circumstancesof dispute to
expose the assumptionsand practicesgoverninghis deploymentof this particular
technology.
'For sociological work on controversies,see H. M. Collins, Changing Order: Replication and
Induction in Scientific Practice (London/BeverlyHills: Sage, 1985); and Collins, ed., Knowledge
and Controversy:Studies of Modern Natural Science, special issue of Social Studies of Science,
1981, 11(1). Historical studies include Steven Shapin and Simon Schaffer,Leviathanand the AirPump: Hobbes, Boyle and the ExperimentalLife (Princeton:PrincetonUniv. Press, 1985); Martin
J. S. Rudwick, The GreatDevonian Controversy:The Shapingof ScientificKnowledgeamong Gentlemanly Specialists (Chicago: Univ. Chicago Press, 1985); and James A. Secord, Controversyin
VictorianGeology: The Cambrian-SilurianDispute (Princeton:PrincetonUniv. Press, 1986).
4Carleton Perrin, "The Triumphof the Antiphlogistians$'in The Analytic Spirit: Essays in the
History of Science in Honor of Henry Guerlac, ed. HarryWoolf (Ithaca,N.Y.: Cornell Univ. Press,
1981), pp. 40-63. Other work on the controversyincludes Karl Hufbauer,The Formationof the
GermanChemical Community(1720-1795) (Berkeley/LosAngeles: Univ. CaliforniaPress, 1982);
JohnG. McEvoy,"TheEnlightenmentandthe ChemicalRevolution"in Metaphysicsand Philosophy
of Science in the Seventeenthand EighteenthCenturies:Essays in Honour of Gerd Buchdahl, ed.
R. S. Woolhouse (Dordrecht:Kluwer Academic, 1988), pp. 307-325; and some of the essays in
ArthurDonovan,ed., The ChemicalRevolution:Essays in Reinterpretation,Osiris, 2nd ser., 1988, 4.
5Trevor H. Levere, "Lavoisier:Language, Instruments,and the Chemical Revolution"in Nature
Experimentand the Sciences, ed. Levere and W. R. Shea (Dordrecht:KluwerAcademic 1990), pp.
207-233; FredericLawrenceHolmes, Eighteenth-CenturyChemistryas an InvestigativeEnterprise
(Berkeley: Office for History of Science and Technology,Univ. California, 1989), esp. Ch. 5; and
ArthurDonovan,"Lavoisierand the Origins of ModernChemistry,"Osiris, 1988, 4:214-231.
32
JAN GOLINSKI
Controversyenables us to see how materialapparatusis embeddedin specific
settingsof practicethatenableit to functionas a tool of investigationandpersuasion.
We shall see thatLavoisierhad to mobilize particularpersonneland their skills to
craft and use his instruments.He forged links with practitionersof the exact sciences, trainedin the Frenchmathematicalengineeringtradition,and with skilled
instrumentmakers.6He expendedsubstantialfinancialresourceson the construction
of his apparatus.He mastereddifficulttechniquesof measurementandcalculationin calibration,for example.He also constructedsocial and literary"technologies,"
managingthe audiencesat set-pieceexperimentaldemonstrationsandconveyingthe
resultsin a writtenform that stressedthe accuracyof the proceduresand the high
standardof proof therebyachieved. In the ongoing controversy,many aspects of
this formof practicewere madeexplicit in the courseof challengesto, anddefenses
of, Lavoisier'sclaims.
Outside Lavoisier'sown setting, his instrumentsdid not always convey their
hoped-forpersuasivepotential.Manyresourcesenabledopponentssuch as Priestley
andKeirto evadethe purportedimplicationsof his experiments.Priestleyarticulated
a radicallydifferentmodel of scientific practiceand condemnedLavoisier'ssupposed accuracyas the spuriousresultof excessivelycomplexexperimentalcontrivances. For Priestley,his own inability to replicatethe Frenchexperimentswas a
reason not to trustthem. Thus discussion of instrumentswas implicatedin wider
debatesaboutthe way science should be practiced.Arguably,the controversywas
not just about the facts of chemical phenomenabut abouthow science should be
carriedon. In the face of such radicaldisagreement,Lavoisier'sinstrumentssimply
could not conveytheirmeaningunequivocally.
Nonetheless,the controversywas eventuallybroughtto a close, albeit in a prolonged and confusedway thatdeservesfurtherinvestigation.It seems clear thatthe
extensionof Lavoisier'spracticesof instrumentaluse playeda partin this process.
His victory(to a certainextenta posthumousone) reliedupontransmittinga culture
of experimentalpracticeto supportdiffusion of his instrumentsand replicationof
the phenomenathey produced.
I. LAVOISIER'SINSTRUMENTALSTRATEGY
By the late 1770s, Lavoisierhad convincedhimself of the need to reformchemical
theoryfundamentallyand to dispense with the notion of phlogiston.In his "crucial
year"of 1772 he hadstudiedthe calcinationof metalsandthe combustionof sulphur
and phosphorusand had establishedthe fixationof air in these processes.He then
followed up Priestley'sisolation of "dephlogisticatedair,"repeatingthe operation
6
The classic studies of Lavoisier'sinstrumentsare MauriceDaumas,Lavoisier: Theoricienet experimentateur(Paris:Presses Universitairesde France, 1955), esp. Ch. 6; Daumas, "Les appareils
d'experimentationde Lavoisier,"Chymia 1950, 3:45-62; and Daumas, "Precisionof Measurement
and Physical and Chemical Research in the EighteenthCentury,"in Scientific Change: Historical
Studies,ed. A. C. Crombie(London:Heinemann,1963), pp. 418-430. On the Frenchmathematical
engineeringtraditionsee C. StewartGillmor,Coulomband the Evolutionof Physics and Engineering
France(Princeton:PrincetonUniv.Press, 1971), esp. Ch. 1; andCharlesCoulin Eighteenth-Century
ston Gillispie, Science and Polity in Franceat the End of the Old Regime(Princeton:PrincetonUniv.
Press, 1980), pp. 506-552.
7For this use of the termtechnologiessee Steven Shapin,"PumpandCircumstance:RobertBoyle's
LiteraryTechnology,"Soc. Stud.Sci., 1984, 14:481-520.
PROOF IN LAVOISIER'SCHEMISTRY
33
for producingit by heatingred mercurycalx. In 1776-1777 he determinedthatthis
"purestpartof the air"was what combinedwith solid substancesin the course of
their calcinationor combustion.He disclosed its role as the portionof the atmosphere consumed in respirationand ascribedto it the power to make substances
acidic thatwas to give it its name, oxygen (the acid generator).8
Lavoisier'sreadinessto deploy new apparatus,borrowingit fromdisciplinesusually consideredbeyondthe boundsof chemistry,hadbeen characteristicof his work
since his early researchesin mineralogyand geology. Alreadyin the 1760s he had
been using thermometricand barometricmeasurementsin geological surveysand
developinghygrometricmethodsfor analyzingmineralwater.It was in the 1780s,
however,thathe beganto exploit physicalinstrumentation
with greaterconsistency
and to deploy it in his campaignagainsttraditionalchemicaltheory.His collaboration with the mathematicalphysicist Pierre-Simonde Laplace in 1782-1783 has
been illuminatedby a classic study by Henry Guerlacand in a stimulatingrecent
paperby Lissa Roberts.9The two collaboratorsdesignedandused a new instrument,
which they introducedin a jointly written"Memoiresur la chaleur"in 1783. As
Robertspoints out, the (initiallyunnamed)machinewas presentedas a purportedly
unproblematicmeasuringdevice for heat exchangesin reactions,the authorsprofessing that it had no particularimplicationsas to the natureof heat. The naming
of the device as a calorimeteroccurredsubsequentlyin the context of Lavoisier's
systematicreconstructionof the disciplinaryprofile of chemistryin his Trait e'le'mentairede chimie (1789). Robertsalso shows that other experimenters,such as
JosiahWedgwoodandAdairCrawford,experienceddifficultiesin replicatingLavoisier andLaplace'sexperimentsanddisputedthe workingof theirmachine.An anonymous writerappearsto havereflectedthe generalappraisal,whenhe wrotein 1797
that,"littlereliance... can be placed on the accuracyof this much-boastedprocess
of the Frenchchemists,"althoughtheirresultshadbeen presented"withall the precision of the new school."10
In the case of the calorimeter,an initial attemptto build a consensus aroundthe
supposedlytheory-neutraluse of a measuringmachine was succeeded by a more
explicitly theoreticaldeploymentof the instrument.Lavoisierwas also, by the mid
1780s, makinguse of othernew apparatusto tryto secureacceptanceof his theories
of combustion,acidity,and the compositionof water.In this period Lavoisier'sinstrumentswere just as much at issue as his substantivetheoreticalclaims. At the
beginningof the decade he had no allies among leading chemists. Most remained
convincedthat phlogistonwas a materialentity releasedfrom burningbodies. Indeed, phlogistonacquireda new lease on life, in the view of many,when it was
identifiedby the IrishchemistRichardKirwanas the basis of "inflammableair"(the
I Henry Guerlac,Lavoisier-The Crucial Year:The
Backgroundand Origin of His First Experiments on Combustionin 1772 (Ithaca,N.Y.: Cornell Univ. Press, 1961); Guerlac,Antoine-Laurent
Lavoisier:Chemistand Revolutionary(New York:Scribners,1975); and FredericL. Holmes, Lavoisier and the Chemistryof Life: An Explorationof Scientific Creativity(Madison:Univ. Wisconsin
Press, 1985).
9 HenryGuerlac,"Chemistryas a Branchof Physics:Laplace'sCollaborationwith Lavoisier,"Historical Studiesin the Physical Sciences, 1976, 7:193-276; andLissa Roberts,"AWordandthe World:
The Significanceof Naming the Calorimeter,"Isis, 1991, 82:198-222.
'0 T. H. Lodwig and W. A. Smeaton, "The Ice Calorimeterof Lavoisierand Laplace and Some of
Its Critics,"Annals of Science, 1974, 31:1-18; andCriticalExaminationof the FirstPartof Lavoisier's
Elementsof Chemistry(London, 1797), pp. 20-21.
34
JAN GOLINSKI
gas Lavoisierwas to call "hydrogen").Kirwanarticulateda theory of combustion
thatwon considerablesupport.In his view the phlogistonreleasedby a burningbody
combinedwith dephlogisticatedair to form fixed air,which then unitedchemically
with the residueof the solid to forma calx or acid. Kirwansaccounthad the appeal
of accommodatingthe weightgain thatwas agreedto occurin instancesof combustion and calcinationwhile maintainingthe existenceof phlogiston."
In the face of this alternativeto his theory of combustion,Lavoisier'sfortunes
turnedon a new issue introducedinto the debatein the early 1780s:the composition
of water.In 1781 HenryCavendishproducedwaterfrom a mixtureof inflammable
anddephlogisticatedairsignitedby an electricspark.The experimentemergedfrom
the traditionof eudiometry,in which the "goodness"of a sampleair was measured
by phlogistication(in this case by sparkingwith inflammableair)andmeasuringthe
diminutionin volume. The productionof water in the reactionwas a quite unexpected result. Cavendishcanvasseda couple of explanations,suggesting that the
more likely one was that waterwas part of the compositionof both airs and was
releasedon theircombinationby a kind of condensationreaction.'2
Lavoisierseized on this result,repeatingCavendish'sexperimentbefore its longdelayedpublication.In June 1783, with the assistanceof Laplaceandin the presence
of CharlesBlagden (Cavendish'sassistant)and witnesses from the Academie des
Sciences, Lavoisierignitedjets of the two airsovermercuryin a sealed glass vessel.
The experimentmade use of two pneumaticchests that he had recently had constructedfor storingthe gases. Lavoisierimmediatelyannounceda new interpretation
of the reaction,statingthat waterwas the sole productof combinationof the two
gases andhence was not an element,as Cavendishand all otherchemistshad maintained,but a compound.'3This interpretationexplainedtwo classes of phenomena
that had previouslyconstitutedtroublesomeanomaliesfor his theory.The inflammableairgeneratedby metalswhen they dissolvedin acids could now be explained
as a productof the decompositionof water,while the reductionof lead calx and
othercalxes by inflammableair could be understoodin termsof the combinationof
the gas with oxygen from the calx (or oxide) to synthesizewater.
Lavoisier'sinterpretationof the reaction was not, however,accepted by other
chemists.Cavendish,when he finallypublishedthe accountof his own experiment
in 1784, referredto Lavoisier'santiphlogisticexplanationbut professedhimself unconvinced:'As the commonlyreceivedprincipleof phlogistonexplainsall phenomena, at least as well as Mr.LAVOISIER'S,I haveadheredto that."14 JamesWatt,the
Birminghamsteam-enginemanufacturerand a friend of Priestley,made a similar
distinctionbetweenthe facts reportedby the Frenchexperimentersandthe interpretive gloss they had laid over them. Wattwrote to Deluc that he had no reason to
doubt the credibilityof the factual reportthat water was the sole productof the
reactionand its weight equal to thatof the two gases: "Fromthe characteryou give
" RichardKirwan,"Remarkson Mr.Cavendish'sExperimentson Air,"PhilosophicalTransactions
of the Royal Society, 1784, 74:154-169; and Michael Donovan, "BiographicalAccount of the Late
RichardKirwan,Esq.,"Proceedingsof the Royal IrishAcademy,1850, 4: lxxxi-cxviii.
12 Henry Cavendish,"Experiments
on Air,"Phil. Trans.,1784, 74:119-153.
13 A. L. Lavoisier,"M6moiredans lequel on a pour objet de prouverque leau n'est point une
substancesimple,"Oeuvresde Lavoisier ed. J. B. Dumas and EdouardGrimaux,6 vols. (Paris:ImprimerieNationale, 1864-1893), Vol. II, pp. 334-359.
14 Cavendish,"Experimentson Air" (cit. n. 12), p. 152.
PROOF IN LAVOISIER'SCHEMISTRY
35
me of the gentlemenwho madeit, thereis no reasonto doubtof its being madewith
all necessaryprecautionsand accuracy."He was, however,not convincedthat the
experimentwas demonstrativeof the compoundnatureof wateror the nonexistence
of phlogiston.Alternativeways of "solvingthe phenomena,"which were "asplausible as any other conjectureswhich have been formed on the subject,' remained
open.'5Watt'sconjecturedexplanationwas very like Cavendish's.Dephlogisticated
air was waterdeprivedof phlogistonandwith its latentheatbound;inflammableair
was phlogistonplus a little waterand latentheat. When the two airs united, water
was releasedalong with heat.
Lavoisierwas thusmadeawarethata morepersuasiveproofthanthe Junedemonstrationwas needed if his contentionof the compoundnatureof waterwere to be
accepted.In the autumnand winterof 1783/84 he laboredto providesuch a proof.
His approachwas to attemptmore accuratemeasurementof the quantitiesof reactantsandproducts,following the lead of GaspardMonge,instructorin experimental physics at the military engineering academy,the Ecole Royale du Genie, at
Mezieres.In Juneand July 1783 Monge had conductedhis own experimentson the
synthesisof waterindependentlyof Lavoisier's,measuringthe volumesand specific
weights of the reactantgases and thus establishingtheir (almostexact) equalityto
the weight of waterproduced.Such a quantitativeapproachappealedto Lavoisier
because it seemed to offer the rigorof a geometricalstandardof proof, since "it is
no less truein physics thanin geometrythatthe whole is equal to its parts.?16
To repeatthe quantifiedsynthesisexperiment,Lavoisierwould requirenew vessels capableof measuringthe volumes of the gases used; the pneumaticchests he
hademployedwith Laplacewerenot adequatefor this purpose.He thereforeenlisted
the help of Jean-BaptisteMeusnier,a formerpupil of Monge'sat Mezieres,who set
to designing appropriatevessels and having them constructedby the instrument
maker Pierre Megnie. Meanwhile Lavoisierand Meusnierworked on an experiment to demonstratethe compoundnatureof waterby decomposingit into its constituentgases. They passed steamthrougha red-hotiron gun barrel.The steamwas
takento be decomposed,its oxygen unitingwith the iron to form an oxide and its
inflammableair emergingfrom the pipe to be collected along with undecomposed
water.Lavoisierreportedthe success to the Academie in April 1784 and subsequently publishedthe account. Although he admittedthat the proportionsof the
constituentsof water could not yet be calculatedwith "mathematicalprecision,"
since the gun barrelhad also undergoneoxidation on the externalsurface while
being heated, he nonethelessproposedthe experimentas a "demonstrativeproof"
thatwaterwas a compound.'7
Again, however,dissensioncontinued.KirwanandPriestleydeniedto Lavoisier's
experimentsthe implicationtheirauthorsoughtto give them.Both insistedthatthe
proposedanalysis of waterwas no such thing. What had happenedwas that phlogiston (inflammableair) had been displaced from iron by combinationof water
with the metal. In February1785 Priestleydescribedto the Royal Society his own
15 JamesWatt,"Thoughtson the ConstituentPartsof Water,"
Phil. Trans.,1784, 74:329-353, esp.
pp. 329, 333.
16
Lavoisier,"M6moiredans lequel on a pour objet"(cit. n. 13), p. 339.
17 A. L. Lavoisierand J. B. Meusnier,"M6moireoi l'on prouve, par la decompositionde 'eau,
que ce fluiden'estpoint une substancesimple,"Oeuvresde Lavoisier(cit. n. 13), Vol. II, pp. 360-373,
esp. p. 371.
36
JAN GOLINSKI
replicationof LavoisierandMeusnier'sexperiment,in which he used measurements
of weights of reactantsto show thatthe sourceof the inflammableair was the iron,
not the water.As had Cavendishand Watt,PriestleychargedLavoisierwith transgressingthe conventionthatexperimentalphilosophersshouldsimplydescribewhat
they observedandnot go beyondthatto impose hypotheticalrationalizationson the
phenomena:"Whilstphilosophersare faithful narratorsof what they observe, no
person can justly complainof being misled by them; for to reason from the facts
with which they are suppliedis no more the provinceof the personwho discovers
them,thanof him to whom they are discovered."18
Facing this persistentoppositionto his claim thatwaterwas a compoundof two
gases, Lavoisiercontinuedto seek a more stringentand compellingproof, to push
backthe boundarythathis criticshaderectedbetweenthe "facts"of experimentand
what they insisted could only be an interpretationor "hypothesis."He workedto
make the compoundnatureof water into a fact-a direct, unmediatedinference
from experiment,permittingno possibility of doubt. This was to be done by employing new, more refinedapparatusto yield quantitativeweight measurementsof
an unprecedentedaccuracy.His effortsculminatedin a large-scaleset-piecedemonstrationof the analysis and synthesis of water in the Paris Arsenal on 27 and 28
February1785. On that occasion Lavoisierassembledall the elements of his form
of experimentalpracticeto conveya demonstrativeproofof his claims;his apparatus
was deployedin the full settingdesignedto maximizeits persuasiveefficacy.19
The analyticpartof the 1785 experimentwas relativelylittle changedfrom what
Lavoisierand Meusnierhad accomplishedthe previousyear. But the operationto
synthesizewaterfromits componentgases was performedwith unprecedentedcare
and very sophisticatednew apparatus.Preparingfor the experiment,Lavoisierfurtherexploitedhis linkswithpersonneltrainedin the mathematicalengineeringtradition and with the skilled instrumentmakerswho served it. He continuedto work
with Laplace and Meusnierand recruitedMonge to help with the synthesis. The
instrumentmakerMegnie producedthe new pneumaticvessels designedby Meusnier towardsthe end of 1783 and was paid 338 livres for them. He also built two
new balancesfor Lavoisier,using novel techniquesto suspendthe beams anddamp
theiroscillations.The largerof these two was estimatedto be capableof weighing
one poundwith an accuracyof about 1 in 100,000. For all his work for Lavoisier,
Megnie was paid 1,814 livres duringthe years 1783-1785. No more than400 livres
of this came from the Academie, the remainderfrom Lavoisier'spersonalwealth.
In straightforward
financialterms,Lavoisierwas investingsubstantialresourcesin
apparatusthatwould serve his purposes.20
The new pneumaticvessels were describedin a paper publishedby Meusnier.
Like the calorimeter,the instrumentLavoisierwas subsequentlyto name the "gasometer"was introducedinitiallyas an anonymousappareilor machine.It was, said
18
JosephPriestley,"Experimentsand ObservationsRelatingto Air and Water,"Phil. Trans.,1785,
75:279-309, esp. p. 280.
19MauriceDaumasandDenis Duveen, "Lavoisier'sRelativelyUnknownLarge-ScaleDecomposition and Synthesis of Water,February27 and 28, 1785,"Chymia, 1959, 5:113-129; and Holmes,
Lavoisierand the Chemistryof Life (cit. n. 8), pp. 237-238.
20 Daumas, Lavoisier (cit. n. 6), p. 149. Comparethe 600 livres that Lavoisierpaid the tinplate
workerNaudinfor the two calorimetershe constructed.Roberts,"WordandWorld"(cit. n. 9), makes
the telling comparisonwith the averagedaily wages of a skilled worker:1/2-2/2 livres.
PROOF IN LAVOISIER'SCHEMISTRY
37
Meusnier,a "universalinstrument"to manipulatevolumesof gases, "bya perfectly
uniformflow,variableat will, andgiving, at each instant,the measureof the quantity
of air used with all the precisionthatone can desire.21The device was based on the
principleof the pneumatictrough,used by numerouseighteenth-centurychemists
to store gases over water (see Figure 1). An uppertank, open at the bottom, was
suspendedfrom a counterweightedbeam so thatit could move up and down within
a lower tankcontainingwater.Pipes enteredthe tankto introducethe gas as it was
preparedandto let it out as required.The crossbeamhad arcsof circles mountedon
each end to equalizefrictionalresistanceto motionat all positionsof the uppertank,
which was suspendedby a chain designednot to elongateundertension.
Meusnier'smajordesign innovationwas a means of ensuringa constantflow of
gas out of the apparatus.To achieve this, a constantpressurehad to be maintained.
But as the upper tank descended it would displace water and therebyreduce the
pressureon the gas. To compensatefor this Archimedeanthrust,Meusnierdesigned
an ingenious modificationto the beam armthat suspendedthe counterweight.The
end of the armwas displacedparallelto the remainderof it, so that the momentof
the counterweightaroundthe fulcrumwould be differentfor differentpositions of
the beam.The linearvariationin effective counterweightcompensatedfor the linear
variationin pressureof the gas due to Archimedes'principle.A long screw connected the displacedpartof the arm to the rest of the beam, so that the degree of
displacementcould be adjustedto set a particularpressure.A scale mountedbeside
the screw enabled this to be measured.Anotherscale, on the arc of the arm suspending the tank, was read against a pointer mountedin a fixed position on the
fulcrumpillar.This scale could be calibratedto give the volumeof gas containedin
the vessel. And the pressureof the gas could be read from a water manometer
mountedon the outside of the lower tankand connectedwith the interior.
Twogasometerswererequiredfor the synthesisexperiment:one each for the oxygen and the hydrogen(see Figure2). Towardsthe end of December 1784 Lavoisier
and his collaboratorsbegan operationsto calibratethem. For each instrumentthis
was a two-stageprocess,requiringseveraldays' work.First,the screw of the counterweightarmwas adjustedwhile the pressureof gas in the vessel was observedon
the water manometer.Appropriatepositions on the scale were noted to maintain
differentset pressures:one inch (of water,aboveatmosphericpressure),two inches,
threeinches, and so on. Each settingwould producea different,but constant,speed
of gas flow. In the second stage the volumes of gas in the vessel, correspondingto
differentpositionsof the pointeragainstthe otherscale, were determined.This was
done by filling bottles of known capacitywith air drawnfrom the gasometerand
noting the change in the pointerposition.This was done severaltimes, with bottles
of different sizes, to overcome inequalities in the width of the tank at different
heights. When the scale had been calibratedin terms of volume, the conversion
could be made to weight by consultingpreparedtables of the densities of the two
gases undervariousconditionsof temperatureand pressure.22
21 J. B. Meusnier, "Descriptiond'un appareilpropre 'amanoeuvrerdiffdrentesespeces d'air,"in
Oeuvresde Lavoisier (cit. n. 13), Vol. II, pp. 432-440.
22
This accountis drawnfrom Daumas andDuveen, "Lavoisier'sLarge-ScaleDecomposition"(cit.
n. 19); Meusnier,"Description"(cit. n. 21); and A. L. Lavoisier,TraitW
e1ementairede chimie,presente dans un ordre nouveau, et d'apres les dicouvertes modernes, 2 vols. (Paris, 1789), Vol. II,
pp. 346-360.
38
JAN GOLINSKI
The success of the calibrationsdepended,of course, on the variousskills of the
experimenters,not least theirtacit knowledgeof the apparatusthey were handling.
Accuracywas strivenfor in all the measurementstaken.The positionof the pointer
againstthe limb scale was readto two places of decimalsof a degreeof arc,by use
of an attachedvernier.Vernierswere apparentlyalso fitted to the thermometer,
which was read to one decimal place of a degree Reaumur,and to the barometer,
which was read to one decimal place of a line of mercury.(One line is V/I2 of an
inch, approximately0.225 cm.) Lavoisierhad been interestedin the accuracyof
thermometersandbarometerssince his earlymineralogicalwork,andhe now put to
use the most advancedprecisionversionsof these instruments.23
The calibrationscompleted, Lavoisierinvited about thirty savants,including a
dozen witnesses nominatedby the Academie, to attend the demonstration.The
course of the experimentshas been well describedby Daumasand Duveen.24The
firstanalysiswas begunon the morningof 27 February,and more thanten bell jars
were filled with hydrogengas and measured.This hydrogenwas used in the first
synthesisexperimentlaterthe sameday.One of the two gasometerswas loadedwith
the gas, the otherhavingbeen filled with oxygen obtainedfromheatingred mercury
calx. A jet of hydrogenwas led into thereactionvessel, whichwas filledwithoxygen
and connectedwith the oxygen-holdinggasometer.Aftera few failures,thejet was
ignited by a sparkfrom an electricalmachineowned by Lavoisier.While the constantflow of gases from the gasometerscontinued,the combustionwas maintained
for about three hours. The following morning,both gasometerswere refilled and
the combustionresumed,while a second analysiswas performedto producemore
hydrogen.This had in turnbeen consumedin the synthesisexperimentby the end
of the eveningof 28 February.Furtherworkwas done on the following days,though
it was less carefullywitnessedand recorded.The waterproducedby the synthesis
reactionwas carefullyweighedandanalyzed,as was the residualgas in the reaction
vessel. Finally,the weightsof reactantsandproductsin the two analysesandthe one
(discontinuous)synthesiswere calculated.
The circumstancesand resultsof the demonstrationmade it convincingto many
of those who took part.Lavoisierhad not so much mounteda show as providedan
opportunityfor his colleagues to participatein a well-organizedteam effort. The
academiciansinspectedthe apparatus,took measurements,and signed theirnames
to the recordsof the results.The proceduresof witnessing,recording,andcertifying
both guaranteedthe authenticityof the resultsand gave the participantsa stake in
theirvalidity.Monge and manyof the mathematiciansandphysicistsin the Academie confirmedtheirsupportfor Lavoisier'sdoctrine.The crucialconversionwas that
of the chemist Claude-LouisBerthollet, who wrote enthusiasticallyto Blagden
about the demonstrationand, in a paper read to the Academie on 6 April 1785,
announcedthat he had been convinced by "the beautifulexperiment"that water
23
Estimatesof accuracyof measurementaredrawnfromexaminationof notes fromthe experiment
survivingin the LavoisierMSS, History of Science Collection, Cornell UniversityLibrary,Ithaca,
N.Y, MSS 3.04, 9.02a-d, 9.03a-d, 9.04a-c, 9.05, 9.06, 9.07a-b, 9.08, 9.09, 9.10, and 9.11a-c. On
the accuracyof thermometersand barometerssee TheodoreS. Feldman,"LateEnlightenmentMeteorology,"in The QuantifyingSpirit in the EighteenthCentury,ed. Tore Fringsmyr,J. L. Heilbron,
and Robin E. Rider(Berkeley/LosAngeles: Univ. CaliforniaPress, 1990), pp. 143-177, on pp. 156157, 166.
24 Daumas and Duveen, "Lavoisier's
Large-ScaleDecomposition"(cit. n. 19), pp. 123-126.
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PROOF IN LAVOISIER'SCHEMISTRY
41
was indeed a compound.25
Not everyonewas so convinced:the chemistsBalthazarGeorges Sage and AntoineBaume, who were presentat the Arsenal,remainedopposed to Lavoisier'stheory.26But in generalit appearsthatLavoisierhad managed
the social technology of convincing his audience at the demonstrationalmost as
successfullyas he had manipulatedthe materialtechnologyof his apparatus.
Persuadinga wider audiencewas however a differentmatter.On this occasion,
Lavoisier'sliterarytechnologyuntypicallylet him down. A brief accountof the experiment,probablybased on draftsby Lavoisier,appearedunderMeusnier'sname
in the Journal Polytype des Sciences et des Arts in February 1786.27Meusnier was
apparentlyalso charged with producing a comprehensivereport, but this never
emerged.In 1789 Bertholletwas still apologizingfor the fact that Meusnier'sabsence fromParison militarydutieshad preventedhim from completingthe work.28
The accountthat did appeargave only an incompleteimpressionof the sophistication of the apparatusand the precautionstakenin its use. No descriptionwas given
of the calibrationproceduresfor the gasometersor the meticulous care taken to
ensurethe accuracyof the measurements.Somewhatout of the blue, Meusnierannounced a rounded-offfigure for the proportionsof the componentsof water:85
percentoxygen and 15 percenthydrogen,by weight; a figure that was within the
rangeof the resultsobtainedbut not unambiguouslyproven.The ratherthin account
was buttressedby a somewhat dogmatic and aggressive rhetoric.Readers were
bluntlytold thatthe descriptionwas "morethansufficientto lay hold of the certainty
of the proposition"that waterhadjust this composition.And the paperconcluded
by promisingthatmethodsof precisionmeasurementofferedthe prospectof uniting
chemistrywith the other physical sciences and advancingto make discoveriesof
unprecedentedcertainty.29
II. THE CRITICS OF THE STRATEGY
Perhapsunsurprisingly,many chemists,particularlyoutside France,were not convinced. In Britain,KirwanandPriestleycontinuedto voice objectionsto the compositionof waterandgainedsignificantsupport.In France,Jean-Claudede Lametherie
keptup a steadybarrageof criticismfor the remainderof the 1780s. In the Observations et MWmoiressur la Physique, of which he assumed the editorship in 1785,
Lametheriecoordinatedthe anti-Lavoisianforces, publishingthe views of such critics as Sage andDeluc, translatingpapersby Priestleyand Keir,andlaunchingregular attacksin his "Discourspreliminaire"at the frontof each annualvolume.30
Variousalternativeinterpretationsof Lavoisier'sprizedanalysisand synthesisreactions were advanced.In his Essay on Phlogiston (1787) Kirwanproposedthat
25 C.-L. Berthollet, "Memoire sur l'acide marin dephlogistique,"Observationssur la Physique,
1785, 26:321-325, esp. p. 324; and H. E. LeGrand,"The 'Conversion'of C.-L. Bertholletto Lavoisier'sChemistry,"Ambix, 1975, 22:58-70, esp. pp. 67-68.
26
Perin, "Triumphof Antiphlogistians"(cit. n. 4), pp. 49, 55-56, 62.
27 A. L. Lavoisierand J. B. Meusnier,
"D6veloppementdes dermie'rs
experiencessur la decomposition et la recompositionde l'eau,"in Oeuvresde Lavoisier(cit. n. 13), Vol. V, pp. 320-334.
28 C.-L. Berthollet,"Consid6rations
surles exp6riencesde M. Priestley,"Annalesde Chimie,1789,
3:63-114, on p. 70.
29
Lavoisierand Meusnier,"D6veloppement"(cit. n. 27), pp. 205-209; cf. Holmes, Lavoisier(cit.
n. 8), p. 237.
30
See, e.g., J. C. De Lam6therie,"Discours preliminaire,"Obs. Phys., 1787, 30:3-45, esp. pp.
29-45; and Lam6therie,"Discourspr6liminaire,"Obs. Phys., 1789, 34:3-55, esp. pp. 26-29.
42
JAN GOLINSKI
inflammableand dephlogisticatedairs would combine to form water only in the
conditions of extreme heat that Lavoisierhad used. At lower temperaturesthey
would form fixed air,as in normalprocessesof combustion.Of the analysisexperiment,Kirwanreiteratedthe traditionalview thatthe inflammableair emergingfrom
the gun barrelwas phlogistondisplacedfromthe ironby water.3'Priestleyconcurred
with this, buthis view of the supposedsynthesiswas differentfromKirwans.When
he had repeatedCavendish'soriginalexperiment,he had alreadyconcludedthatthe
waterproducedby the reactionof the two gases was presentin theircompositionin
the gaseous state.The experimentshowed only that all "airs"containedsome proportionof water.Therewas, however,anotherproduct,namely"nitrousacid"(later
called nitricacid), which was producedby the combinationof the ponderablebases
of the gases. Until the early 1790s Priestleycontinuedto performthe experiment
airs and to record
with what he still called "inflammable"and "dephlogisticated"
both waterand nitrousacid as the products.AlthoughBertholletand other Lavoisianstriedto cast doubton Priestley'smethods,assertingthatthe acid was the result
of contaminationof his oxygen by atmosphericnitrogen,Priestleyconsistentlydenied such contamination.His position was endorsedby Keir, Deluc, Lametherie,
and Watt,amongothers.32
As well as insisting upon these alternativeexperimentalfacts, Lavoisier'scritics
teased apartthe rhetoricby which he constructedhis claims. Lavoisierhad sought
to have his claims acceptedas facts by assertingthat they followed directlyfrom
precise quantitativemeasurements.In relationto the 1785 demonstrationhe wrote,
accordingto Kirwan'stranslation:
This doubleexperiment... may be regardedas a demonstration,. . . if in any case the
word Demonstration may be employed in natural philosophy and chemistry. ... The
proofs which we have given of the decomposition and recomposition of water being of
the demonstrative order, it is by experiments of the same order, that is to say by demonstrative experiments, which they ought to be attacked.33
Ratherthan acceptingthe challengeto confronthim on his own ground,however,
Lavoisier'sopponentsused variousstrategiesto disconnectwhat were agreedto be
the facts from theirpurportedimplications.
KirwanandWilliamNicholson,the editorof the secondeditionof Kirwan'sEssay
on Phlogiston (1789), focused on the assumedconnectionbetween precision and
demonstration.Kirwanpraised Lavoisier as "the first that introducedan almost
mathematicalprecisioninto experimentalphilosophy,"but deniedthatone or a few
accurateexperimentscould overturndecadesof chemicalexperimentationsupporting the phlogistontheory.There was no possibilitythat a single experimentcould
31 RichardKirwan,An Essay on Phlogiston and the Compositionof Acids, 2nd ed., ed. William
Nicholson (London, 1789), pp. 42-44.
32 Priestley,"Experiments
and Observations"(cit. n. 18), pp. 282, 294-295; JosephPriestley,"Further ExperimentsRelating to the Decomposition of Dephlogisticatedand InflammableAir,"Phil.
Trans.,1791, 81:213-222; J[ames]K[eir], TheFirstPart of a Dictionaryof Chemistry(Birmingham,
(cit. n. 1), pp. 145-146; J. C. de Lamdthe1789), pp. 118-119; Deluc, "Lettrea M. De La MWtherie"
rie, "Mdmoiresur l'air phlogistiqu6(ou impur)obtenue par la combustionde l'air inflammable&
de l'air pur,"Obs.Phys., 1789, 34:227-228; andJamesWattto JosephBlack, 8 June 1788, in Partners
in Science: Lettersof James Wattand JosephBlack, ed. Eric Robinsonand Douglas McKie (London:
Constable,1970), pp. 166-167.
33 Lavoisier,as quoted in Kirwan,Essay on Phlogiston (cit. n. 31), pp. 59-61.
PROOF IN LAVOISIER'SCHEMISTRY
43
be "demonstrative"
of a conclusionas revolutionaryas the notion that waterwas a
compound.Kirwaninsistedthat"thebook of natureshouldbe interpretedlike other
books, the sense of which must be collected ... from an attentiveconsiderationof
the whole."Whenthis was done, contradictionsbetweenLavoisier'sclaims andother
well-establishedexperimentalresultswere not hardto find.Kirwanpointedout that
the decompositionof water was supposedlyeffected by iron but not by charcoal,
while otherfindingsshowedcharcoalhad a greateraffinityfor oxygen thandid iron.
The doctrineof affinitiesyieldedseveralotherproblemsfor the antiphlogistictheory,
as Lavoisierwas obliged to acknowledge.34
Nicholsontook a slightlydifferenttack,in a sophisticatedcritiqueof Lavoisierfor
makingexcessive claims for accuracyof measurement.After discussingthe likely
experimentalerrorsin measurementsof weights andvolumes,Nicholson concluded
that Lavoisier'sfigures,with their long stringsof decimals, "exhibitan unwarrantable pretensionto accuracy."That being so, the rhetoricallink from precision of
measurementto certaintyof conclusion was broken.Measurementsthat showed a
quite spuriousprecision could not be taken as proof of what was asserted.Taking
up Lavoisier'sterminologyof a "demonstrativeorder"of proof, Nicholson wrote:
"Whenthe real degree of accuracyin experimentsis thus hiddenfrom our contemplation,we are somewhatdisposed to doubtwhetherthe exactitudescrupuleuseof
the experimentsbe indeed such as to renderthe proofs de 1'ordre demonstratif"35
In an earlierworkNicholson had alreadydiscussedand dismissedthe possibility
that experimentalknowledge could attainthe certaintyof demonstration.Drawing
upon the resourcesof British empiricistphilosophy,Nicholson had arguedin his
Introduction to Natural Philosophy (1782) that experiments could not convey facts
to the mind with sufficientimmediacyto give them the intuitivecertaintyof mathematicaltruths."Thegreatperspicuityandcertaintyof mathematicalknowledge,"he
wrote, "arisesfrom the simplicity of the ideas employed,and their not depending
on any externalbeing."In experimentaloperations,however,it was not possible to
presentall the relevantaspects of the situationto the mind directlyand simultaneously. Hence, "in general, we must be contentedwith less proof than demonstration."36The results of experimentscould not, therefore,be treatedlike the axioms
of geometry-demonstrative certaintydid not inherein the resultsof experiments,
as Lavoisiermaintained.This appearsto have been the generalview amongBritish
naturalphilosophers,who sharedthe empiricistposition that the senses could not
immediatelyperceive all the elements of a complex experimentalsituation.The
English chemistThomasBeddoes used the same termsin his discussionof the demonstrativestatusof the watercompositionexperiments,in his Observationson the
Nature of Demonstrative Evidence (1793):
What for instanceis it, that preventsme from being as certain,that waterconsists of
hydrogeneand oxygene airs, as of any propositionin Euclid?-nothing surelybut the
incompetencyof my senses. ... Now if I could perceive the small quantityof azotic
air present separatelyuniting with a certainportionof the oxygene air to form acid,
while the hydrogeneair unites with the rest to form water;if I could see that the airs
3
Kirwan,Essay on Phlogiston (cit. n. 31), pp. 7, 304, 317.
35
Ibid., pp. viii, xi.
36 William Nicholson, An Introductionto Natural Philosophy,2 vols. (London, 1782), Vol. I, pp.
1-6, quotationson p. 4.
44
JAN GOLINSKI
previouslycontainonly a little or no waterbeforehand,and if there was no heat and
light, I shouldhavedemonstrativeevidence.
Followinga relatedline of critique,Priestleyalso took aim at the meansby which
Lavoisierhad soughtto demonstratethe factualityof his claims. Priestleyidentified
andbroughtintoquestionseveralelementsof Lavoisier'smaterial,social, andrhetorical techniques,subjectingto scrutinythe validityandreliabilityof instruments,and
the formof practicewithinwhichthey wereputto use. Priestley'sown epistemology
stressedthe autonomyof individualjudgmentandthe equalityof all observers,and
in his view Lavoisierthreatenedto use his privileged access to instrumentalrePriestleyrefused to submithis interpretive
sources to impose his own authority.38
judgmentto whathe took to be such a nakedassertionof power.He chargedLavoisier with using apparatusso complexthathis experimentswereliable to errorandso
expensivethatthey were impossibleto replicate.The apparatusused by the French
academiciansin February1785 was, he wrote, "extremelycomplex, as a view of
theirplates will shew,and mine was perfectlysimple, so thatnothingcan be imagined to be less liable to be a sourceof error."For Lavoisierto use privateresources
to develop specially refinedinstrumentationseemed to Priestleyto indicatehis refusal to submitto the social validationof widespreadreplication.The synthesisexperimentrequired,Priestleynoted, "so difficultandexpensivean apparatus,and so
many precautionsin the use of it, that the frequentrepetitionof the experiment
cannotbe expected;and in these circumstancesthe practisedexperimentercannot
help suspectingthe certaintyof the conclusion."In 1796 he was still insistingthat
the criticalexperimenton compositionof waterhad"notbeen sufficientlyrepeated."
Summarizinghis position in 1800, he maintained:"Till the Frenchchemists can
maketheirexperimentsin a mannerless operoseandexpensive. .. I shall continue
to thinkmy resultsmore to be dependedupon thantheirs."39
Priestleyand the othercritics showed thatto disputeLavoisier'sclaims required
analysisof the meansby whichthose claimshadbeen renderedas facts. Instruments
thatLavoisierproposedas accurateand refinedwere portrayedby his opponentsas
unnecessarilycomplex and liable to error.His mobilizationof specialist skills and
investmentof substantialfinancialresourcesin his apparatuswere said to point towardsan illegitimateconcentrationof instrumentalpower.This would deny other
investigatorsthe rightto contributetheirown observationsor to replicatehis experiments.His use of methodsof precisionmeasurementwas also denouncedas claiming an unjustifieddegreeof accuracy,and its purportedconnectionwith a "demonstrativeorder"of proof was denied.In these respectsLavoisier'sopponentspointed
to the fragilityof his experimentalpractice;they deniedthatthe phenomenahe had
producedcould be reproducedin othersettings.
37 Thomas Beddoes, Observationson the Nature of DemonstrativeEvidence (London, 1793), pp.
108-109.
and ChemicalRevolution"(cit. n. 4), pp. 205-209.
38 Cf. McEvoy,"Enlightenment
39 JosephPriestley,Considerationson the Doctrine of Phlogistonand the Decompositionof Water
(Philadelphia,1796), ed. William Foster (Princeton:PrincetonUniv. Press, 1929), pp. 17, 34, 41;
and Priestley,The Doctrine of PhlogistonEstablishedand that of the Compositionof WaterRefuted
Pa., 1800), pp. xi, 48, 50, 76-77.
(Northumberland,
PROOF IN LAVOISIER'SCHEMISTRY
45
III. REPRODUCINGLAVOISIER'STECHNOLOGY
Althoughthe controversycontinuedfor severalyears,Lavoisier'sinstrumentseventually proved themselves relatively robust tools for extending acceptanceof his
claims.He showedthatit was possibleto replicatehis crucialexperiments,including
those on the compositionof water.This requiredreproducingcertainfeaturesof the
setting of the original experimentsat other sites. A certainamountof redesign of
materialtechnology and its supportingpracticeswas also called for. To the extent
thatthis succeededandthe samephenomenaweretakento be reproducedelsewhere,
the controversywas steadilyclosed in Lavoisier'sfavor.
One relatively well documentedepisode in this process is that concerningthe
Dutch chemist and experimentalphilosopherMartinusvan Marum.Van Marum
traveled to Paris in July 1785, a few months after the dramaticanalysis-andsynthesisdemonstration.Althoughunableto witnessthatevent,he had a briefmeeting with Lavoisierand several conversationswith Monge regardingthe new antiphlogistic theory.Returningto the Netherlands,he workedto replicateLavoisier's
experimentsand, in February1787, wrote to Lavoisierand Monge declaringhis
allegianceto the new chemistry.40
He thendevotedhimselfto convertingotherDutch
chemists.The criticalnecessity,as he realized,was for convincingand widespread
replicationsof the relevantexperiments,of which that on the synthesis of water
seemed most important.This experiment,he noted, "hadnot previouslybeen performed outside Paris."Dutch chemists had remainedskepticalbecause "theyhad
had no opportunityto see or to repeatexperiments,the resultsof which formedthe
basic principlesof the new chemicaltheory.Indeed,the necessaryapparatusas made
by the generousLavoisierat his own expense could hardlybe obtained,owing to its
expensivenessand to the difficultyof constructingit with the precisionrequired'"
In particular,the gasometersrequiredfor the synthesis experimentwere prohibitively costly.4'
Using the resourcesof Teyler'sMuseumin Haarlem,van Marumsolved the problem by significantlysimplifyingMeusnier'sdesign. Insteadof a moving tank suspended by a counterweightedbeam, van Marum'sapparatusused two vessels: one
containingthe gas over water,the othera constanthead of water(maintainedby an
adjustabletap on a feeder vessel) to keep up a steadypressureandregulatethe gas
flow.Linearscales attachedto the side of the gas-containingvessel enabledthe water
level, andhence the gas volume,to be measured.Withthis simplifiedapparatus,van
Marumfirstperformedthe synthesisexperimentin Haarlemin 1791, "beforeall the
40 Martinusvan Marumto Lavoisier,26 Feb. 1787; and van Marumto Monge, 26 Feb. 1787, in
Martinusvan Marum:Life and Work,ed. R. J. Forbes,E. LeFebvre,and J. G. Bruijn,6 vols. (Haarlem: Tjeenk, Willink & Zoon, 1969-1976), Vol. I, pp. 193-194, 255-256. See also T. H. Levere,
"Martinusvan Marumand the Introductionof Lavoisier'sChemistryin the Netherlands,"ibid., pp.
158-286; andH. A. M. Snelders,"TheNew Chemistryin the Netherlands,"Osiris, 1988, 4:121-145,
esp. pp. 127-130.
41 Martinusvan Marum,"Lettre'aM. Berthollet,contenantla descriptiond'un gazometreconstruit
d'une manierediff6rentede celui de MM. Lavoisier& Meusnier,"Ann. Chimie, 1792, 12:113-140,
trans. in Martinusvan Marum,ed. Forbes, LeFebvre,and Bruijn (cit. n. 40), Vol. V, pp. 245-259,
241-242 (quotations).A parallelmay be the slow replicationoutsideFranceof Coulomb'sdetermination of the law of electrostatic force, which was also embedded in the local practices of French
engineeringphysics. See J. L. Heilbron,Electricityin the Seventeenthand EighteenthCenturies:A
Studyof Early ModernPhysics (Berkeley:Univ. CaliforniaPress, 1979), pp. 475-476.
46
JAN GOLINSKI
devotees of Physics or Chemistry who desired to be present." The result was a significant success for the Lavoisian theory. Van Marum recorded: "The simple and
less costly gasometers I had used for this experiment were ordered here and imitated
elsewhere, in order to repeat it in several places."42
Notwithstanding van Marum's claim that his apparatus allowed the synthesis experiment to be performed "with all the accuracy that can be desired," it seems clear
that replicability was bought at the cost of some degree of precision. Van Marum
declined to give any figures for the results of his experiments, saying only that they
were "perfectly in agreement" with those of Lavoisier and his allies.43 Nor did he
give an account of the calibration of his gasometers or the calculations to reduce gas
volumes to weights. Perhaps a display of precise measurement and calculation of
the kind Lavoisier had mounted in 1785 was not necessary in the context in which
van Marum performed his demonstrations. More important for winning over a more
extensive audience was a version of the experiment that could readily be replicated
in a large number of locations.
To this extent van Marum had succeeded by departing from Lavoisier's own rather
uncompromising attitude to replication of his apparatus. In the Traite Lavoisier
had written:
In the presentadvancedstate of chemistry,very expensive and complicatedinstruments are become indispensablynecessaryfor ascertainingthe analysisand synthesis
of bodieswith the requisiteprecisionas to quantityandproportion;it is certainlyproper
to endeavourto simplify these, and to renderthem less costly; but this ought by no
means to be attemptedat the expense of their conveniencyof application,and much
less of theiraccuracy.44
In the event, simplifying and cheapening instruments did usually mean sacrificing
their accuracy. But to extend acceptance of Lavoisier's chemical theories, the price
was worth paying.
IV. CONCLUSION
Historians have noted how the "Chemical Revolution" brought with it new experimental apparatusand new standards of accurate measurement. What might not have
been appreciated and certainly deserves further investigation is how integral these
developments were to the achievement of Lavoisier and his allies. The lengthy and
wide-ranging controversy he provoked inevitably raised numerous issues about the
nature of scientific practice. The process of reaching a decision as to the facts of
chemical phenomena was at the same time the formation of a consensus concerning
how chemistry should be done. The program comprised a nomenclature and a textbook rhetoric; it was promulgated through social structures of communication and
discipline; and it was embodied in new instrumentation and skills. Having triumphed, the revolution determined how history should be written: van Marum's
VanMarum,"Letterto M. Berthollet"(cit, n. 41), p. 242.
Ibid., pp. 250, 251, 255.
44 Lavoisier,Traits6ljmentaireII, pp. 359-360, trans.RobertKerr,in Elementsof Chemistryin a
New SystematicOrder,Containingall the ModernDiscoveries (Edinburgh:WilliamCreech, 1790),
p. 319.
42
43
PROOF IN LAVOISIER'SCHEMISTRY
47
experimentswere warrantedas valid replicationsof Lavoisier's,while Priestley's
were condemnedas crudeand contaminated.
Clearly,one task that historiansshould set themselvesis to overcomethis retrospectiveshapingof events.Anothershouldbe to situatematerialtechnologyin such
a reconstructedhistory.Studyof instrumentationcan lead to more thansterileantiquarianism;it can open the door to a broaderappreciationof all the dimensionsof
scientificpractice.A focus on controversiesenables us to graspthe importanceof
the materialcultureof science, becausewhen apparatusis disputedthe connections
with specific formsof practiceanddiscourseareexposed.The links betweeninstruments and their usage and interpretationare explicatedin the course of attackor
defense. We learnboth that science is embodiedin firmlymaterialthings and that
it is nonethelesssocially negotiatedandhistoricallyvariable.