Slides

PHLOGISTON THEORY
ENGLISH FOR YOUNG PHYSICISTS
WS 2009/2010
DR. SÖREN LANGE
Robert Zeise
“THE SPIRIT”
DO YOU
REALLY BELIEVE IN
THIS...?
C6H12O6 + 6O2 → 6CO2 + 6H2O
2Mg + O2 → 2MgO
2H2O → 2H2 + O2
OVERVIEW
o INTRODUCTION & HISTORICAL
BACKGROUND
o THE ACTUAL PHLOGISTON
THEORY
o THE PHLOGISTON’S FINAL BLOW
INTRODUCTION &
HISTORICAL BACKGROUND
o “ANCIENT TIMES”
EARTH
AIR
FIRE
WATER
(ETHER)
INTRODUCTION &
HISTORICAL BACKGROUND
o 17TH CENTURY: EMPEDOCLES & ARISTOTLE
Combustion frees
small components
(“fire-components”)
of a material.
Combustion is a
changeover of
principles that
leads to another
composition of a
material.
INTRODUCTION &
HISTORICAL BACKGROUND
o THE THEORIES HAD TWO THINGS IN
COMMON:
n COMBUSTION CAUSED THE DEMOLITION OF
MATERIALS
n UNKNOWN ELEMENTS WERE RELEASED
COMBUSTION WAS (BELIEVED TO BE)
THE MOST IMPORTANT REACTION;
UNDERSTANDING COMBUSTION
WOULD BE A SCIENTIFIC REVOLUTION.
INTRODUCTION &
HISTORICAL BACKGROUND
o PHLOGISTON THEORY WAS A SCIENTIFIC
CONCEPT TO EXPLAIN THIS PROCESS.
o “CORROSION OF METALS IS A FORM OF
COMBUSTION, SO IS RESPIRATION IN
ANIMALS”
o 1667:
J. J. BECHER PUBLISHED HIS
“PHYSICAL EDUCATION” AND
MENTIONED THE WORD PHLOGISTON
FOR THE FIRST TIME.
GET SOME
PHYSICAL
EDUCATION!
INTRODUCTION &
HISTORICAL BACKGROUND
o BECHER ELIMINATED “FIRE” & “AIR” FROM
THE “LIST” OF ELEMENTS AND REPLACED
THEM WITH THREE “FORMS” OF EARTH:
n “TERRA LAPIDEA”
n “TERRA FLUIDA”
n “TERRA PINGUIS”
(LATER: “TERRA PINGUIS” = “PHLOGISTON”)
o “PHLOGISTON IS RELEASED WHEN
COMBUSTIBLE SUBSTANCES ARE BURNED.”
INTRODUCTION &
HISTORICAL BACKGROUND
o STAHL DEFINED THE TERM PHLOGISTON AS…
“THE MATTER AND
PRINCIPLE OF FIRE,
CONTAINED IN ALL
METALS AND
COMBUSTIBLE
BODIES AND GIVEN
UP IN BURNING OR
CALCINATIONS.”
THE ACTUAL
PHLOGISTON THEORY
o “ALL FLAMMABLE MATERIALS
CONTAIN PHLOGISTON, A
HYPOTHETICAL SUBSTANCE
WITHOUT TASTE, ODOR, COLOR OR
MASS THAT IS LIBERATED IN
BURNING”
o ONCE BURNED: THE
“DEPHLOGISTICATED” SUBSTANCE
IS IN ITS “TRUE” FORM, THE CALX
o SO “PHLOGISTICATED” SUBSTANCES
CONTAIN PHLOGISTON AND ARE
“DEPHLOGISTICATED” WHEN
BURNED
THE ACTUAL
PHLOGISTON THEORY
o "[...] IN GENERAL, SUBSTANCES THAT BURN IN
AIR ARE RICH IN PHLOGISTON; THE FACT
THAT COMBUSTION SOON CEASES IN AN
ENCLOSED SPACE IS AN EVIDENCE THAT AIR
HAS THE CAPACITY TO ABSORB ONLY A
DEFINITE AMOUNT OF PHLOGISTON. WHEN
AIR HAS BECOME COMPLETELY
PHLOGISTICATED IT CAN NO LONGER
SUPPORT COMBUSTION OF ANY MATERIAL,
NOR SUPPORT LIFE. [...]"
o 1772: NITROGEN IS DISCOVERED
o EXPLANATION: RESIDUE OF AIR LEFT AFTER
BURNING IS “PHLOGISTICATED AIR”
THE ACTUAL
PHLOGISTON THEORY
o COMBUSTION:
WOOD →
CALX (ASH) + PHLOGISTON (TO THE AIR)
IRON →
CALX (RUST) + PHLOGISTON (TO THE AIR)
o ASH (FOR EXAMPLE) IS MUCH LIGHTER THAN
WOOD, SO IT “MAKES SENSE” TO THINK ITS
WEIGHT “IS GIVEN OFF INTO THE AIR”
o CHARCOAL
→ PHLOGISTON (TO THE AIR)
(SMALL RESIDUES ARE IMPURITIES)
THE ACTUAL
PHLOGISTON THEORY
o WOOD BURNS IN A SEALED
CONTAINER NOT TO COMPLETION IF
THERE ISN’T ENOUGH AIR TO HOLD
THE PHLOGISTON (“COMMON AIR”):
WOOD + COMMON AIR
→ CALX + PHLOGISTICATED AIR
o J. PRIESTLEY “DISCOVERED”
ANOTHER FORM OF AIR:
WHEN MERCURY WAS HEATED IN
AIR, IT FORMED A RED SUBSTANCE
WHICH BECAME KNOWN AS THE...
…
PRECIPIATE
PER SE
THE ACTUAL
PHLOGISTON THEORY
o PRECIPIATE PER SE HEATED WITH NO AIR AT
ALL CHANGED BACK INTO MERCURY AND A
“NEW KIND” OF AIR.
o NEW DEFINITION:
“FIXED AIR”
= (WHAT USED TO BE) “PHLOGISTICATED AIR”
(WHAT HAD BEEN CALLED “PHLOGISTICATED
AIR” IS “IN FACT” SOME OTHER KIND OF AIR...
AN IMPURITY OF COMMON AIR, SO:)
o COMMON AIR
= FOUL + DEPHLOGISTICATED AIR
PHLOGISTICATED AIR
= DEPHLOGISTICATED AIR + PHLOGISTON
THE ACTUAL
PHLOGISTON THEORY
o WOOD + DEPHLOGISTICATED AIR
→ CALX (ASH) + PHLOGISTICATED AIR
o MERCURY + DEPHLOGISTICATED AIR
↔ PRECIPIATE PER SE
(PRECIPIATE PER SE = COMBINATION OF
“MERCURY CALX” AND PHLOGISTON)
o WATER WAS SEPARATED BY ELECTROLYSIS
INTO TWO KINDS OF AIR, A “NEW” GAS
CALLED “INFLAMMABLE AIR” AND
“DEPHLOGISTICATED AIR”:
WATER
→ INFLAMMABLE + DEPHLOGISTICATED AIR
THE ACTUAL
PHLOGISTON THEORY
o INFLAMMABLE AIR BURNS EASILY,
FORMING WATER:
INFLAMMABLE + DEPHLOGISTICATED AIR
→ CALX (WATER)
o A QUESTION OCCURED:
IS THE RESULTANT WATER
NOT REALLY THE CALX OF
INFLAMMABLE AIR, BUT
RATHER A COMBINATION OF
THE TRUE CALX AND
PHLOGISTICATED AIR?
THE ACTUAL
PHLOGISTON THEORY
o CONCLUSION:
INFLAMABLE AIR (INSTEAD OF CHARCOAL) IS
“NOW” CONSIDERED TO BE PURE
PHLOGISTON:
WATER =
PHLOGISTON + DEPHLOGISTICATED AIR
o BUT ALSO:
PHLOGISTICATED AIR =
PHLOGISTON + DEPHLOGISTICATED AIR
o ... AND PHLOGISTICATED AIR WAS
CONSIDERED TO BE FIXED AIR...
THE ACTUAL
PHLOGISTON THEORY
o CHARCOAL CONTAINS PHLOGISTON AND
WHEN BURNED, IT GIVES OFF “GASEOUS
CALX” COMBINED WITH WATER
o WATER NOW TAKES THE PLACE OF
PHLOGISTICATED AIR
o GOSH… SO...?
SUMMARY OF THE “LATEST
VERSION” OF OUR THEORY
o WATER
↔ INFLAMMABLE AIR (PHLOGISTON)
+ DEPHLOGISTICATED AIR
o METAL (“PURE BASE” + PHLOGISTON)
+ DEPHLOGISTICATED AIR
→ CALX (“PURE BASE” + WATER)
o CHARCOAL (“PURE BASE” + PHLOGISTON)
+ DEPHLOGISTICATED AIR
→ CALX (FIXED AIR + WATER)
o CALX (“PURE BASE” + WATER) + CHARCOAL
→ METAL (“PURE BASE” + PHLOGISTON) +
FIXED AIR
THE PHLOGISTON‘S
FINAL BLOW
o AS TIME WENT ON MORE AND MORE
“PHLOGISTIANS” BECAME “ANTIPHLOGISTIANS”,
UNTIL ONLY “PRIESTLEY WAS LEFT”.
o PHLOGISTON THEORY WAS INCORRECT IN
QUANTITATIVE EXPERIMENTS:
ANTIPHLOGISTIANS MEASURED THE WEIGHT
OF EVERY SUBSTANCE INVOLVED IN AN
EXPERIMENT (EVEN THE GASES):
WHEN IRON RUSTS AWAY THE RUST WEIGHS
MORE THAN THE ORIGINAL IRON, SO A
PHLOGISTON WOULD HAVE TO HAVE A
NEGATIVE WEIGHT.
o THIS “ATTITUTE” CONVINCED THE MOST OF
THE “LAST” PHLOGISTIANS...
LOSE WEIGHT...
o ... EAT MORE PHLOGISTON!
BACK TO
„THE SPIRIT“
PHLOGISTON THEORY
LAVOISIER THEORY
WOOD + DEPHLOGISTICATED
AIR
→ ASH + PHLOGISTICATED
AIR
C6H12O6 + 6O2
→ 6CO2 + 6H2O
METAL +
DEPHLOGISTICATED AIR
→ RUST + PHLOGISTICATED
AIR
2Mg + O2
→ 2MgO
WATER
→ PHLOGISTON +
DEPHLOGISTICATED AIR
2H2O
→ 2H2 + O2
THE PHLOGISTON‘S
FINAL BLOW
o ONE SHOULD NOT FORGET THE
PHLOGISTIANS WERE SERIOUS SCIENTISTS.
o DURING THE ENTIRE 18TH CENTURY THE
PHLOGISTON THEORY WAS MORE SATISFYING
THAN ANY ALTERNATIVE...
o A. L. DE LAVOISIER:
„COMBUSTION CAUSES
OXIDATION OF
METALS, SO THE METAL
INDUCTS OXYGEN.“
TRANSLATIONS
o “AIR” MEANS “GAS” (OF COURSE)
o “FIXED AIR” MEANS “CARBON DIOXIDE”
(CHARCOAL IS ALMOST PURE CARBON)
o “INFLAMMABLE AIR” MEANS “HYDROGEN”
o “DEPHLOGISTICATED AIR” MEANS “OXYGEN”
o “FOUL AIR” MEANS “NITROGEN”
o “CALX” MEANS “OXIDE”
o “PRECIPIATE PER SE” MEANS “MERCURY
OXIDE”
OUTLOOK
o None...
THE PHLOGISTON‘S
FINAL BLOW
o LAVOISIER TEACHES THAT COMBUSTION
CAUSES SUBSTANCES TO INDUCT ELEMENTS,
WHILE THE PHLOGISTIANS HAD THE IDEA
THAT ELEMENTS (PHLOGISTONS) WERE
GIVEN OFF INTO THE AIR.
o LAVOISIER ALSO DEVELOPED ARISTOTLES’
MEANING OF THE WORD “ELEMENT” AND
DISCOVERED 33 ELEMENTS OF THE PSE.
o BUT...
HOW COULD THE PHLOGISTON THEORY
SURVIVE ALL OF THE „ATTACKS“
AND COME BACK FOR MORE?
SOURCES
o James Bryan Conant “The Overthrow of
Phlogiston Theory: The Chemical
Revolution of 1775–1789” (Cambridge:
Harvard University Press (1950))
o www.wikipedia.org
o www.jimloy.com/physics
o www.answers.com/topic/phlogiston-theory
o www.britannica.com
THANK YOU
FOR YOUR ATTENTION!
QUESTIONS.
ANYONE?