Scientific Revolution
The Scientific Revolution is a term commonly
referring to the transformation of thought
about nature through which the Aristotelian
tradition was replaced by so-called "modern"
science.
Chemical Revolution
• The Greek philosopher Democritus
began the search for a description
of matter more than 2400 years
ago.
• He asked: Could matter be divided
into smaller and smaller pieces
forever, or was there a limit to the
number of times a piece of matter
could be divided?
The Greek Philosopher Democritus
Democritus
c. 460 – c. 370 BC
Atomos
• His theory: Matter could not be
divided into smaller and smaller
pieces forever, eventually the smallest
possible piece would be obtained.
• This piece would be indivisible.
• He named the smallest piece of matter
“atomos,” meaning “can not be cut.”
Democritus
Atomos
§To Democritus, atoms were small, hard
particles that were all made of the same
material but were different shapes and sizes.
§Atoms were infinite in number, always
moving and capable of joining together.
The Greek Philosopher Aristotle
• Believed that matter could be
continuously divided without end
(the “continuous” idea of matter).
• There is no need for empty space.
• There are no atoms. All matter is
made of the natural elements
(earth, water, air and fire.
384-322 BC
The four elements of ancient times (Greek)
• All matter is made up of these four elements
• The above four elements are transmutable
Five interconvertible elements make up the earth
Pancha Bhoota (Sanskrit: प"चभूत), five great elements, which, according to
Hinduism, is the basis of all cosmic creation.
• Prithvi (Sanskrit: पृ+वी:, Earth),
• Jal (Sanskrit: अप:, Water),
• Agni (Sanskrit: अि1न, Fire),
• Vayu (Sanskrit: वायु:, Air),
• Akasha (Sanskrit: आकाश, Space ).
The Indian View
(Taittirīya Upanishad and Aitareya Upanishad, 6th century BC)
Even before Aristotle
Kashyap (Acharya Kanada)
• Vaisheshika school of philosophy
• Vaisheshika Sutras
• 6th century BC
Ancient Indian Atomistic Thoughts
Every object of creation is made of atoms (paramāṇu) which in
turn connect with each other to form molecules (aṇu). Atoms
are eternal, and their combinations constitute the empirical
material world.
The similarity of the early Indian views of matter with the Greek models have led historians
to wonder if communication occurred between the philosophers in these early civilizations.
Alchemy (next 1500 years)
• Mixture of science and mysticism.
• Lab procedures were developed, but alchemists did not
perform controlled experiments like true scientists.
European and Asian philosophers
Alchemists
Phlogistonists
Modern chemists
The Aristotelian tradition and medieval alchemy
eventually gave rise to modern chemistry
Ancient Greeks:
5th century BC to 17th century Earth, Water, Air and Fire
Asians:
5th century BC to 17th century Earth, Water, Air, Fire and Space
Egyptian: Abu Mus-Hayyan
8th century AD Elements + sulfur + mercury
European: Paracelsus, Swiss
16th century AD Elements + {sulfur + mercury+salt}
Alchemists to Phlogistonists
Alchemists laid the groundwork for many chemical processes, such as the refining of ores,
the production of gunpowder, the manufacture of glass and ceramics, leather tanning, and
the production of inks, dyes, and paints. Alchemists also made the first attempts at
organizing and classifying substances so that they could better understand their reactions
and be able to predict the products of their experiments.
Alchemists
300 BC to 17th century
• Transmutation of metals
• Philosophers stone
• Elixir of life
• Interconversion of minerals
• Looking for medicines
Alchemists attempted to transmute
cheap metals to gold. The substance
used for this conversion was called
the Philosopher's Stone.
Arabian origin but was prevalent world over
Alchemists: Middle-East, Greeks, Romans, Asia, Europe
300 BC-17th century
Johann Joachim Becher Replaced Greek and Paracelsus (a Swiss
1635 – 1682 alchemist) element (4+3) with two,
Seven elements became two: earth and water,
air used only as a mixer.
Replaced fire with three types of earth, one
being fatty flammable earth.
Georg Ernst Stahl Kept the proposals of Becher except changed
1659-1734 the name of flammable earth to phlogiston.
Beginnings of Phlogistonists
• The Greek concept of elements was popular for
almost 2200 years.
• Rejected the Aristotelian elements: earth, water,
air, and fire.
• In 1661 Boyle noted that it was impossible to
combine the four Greek elements to form any
substance and it was equally impossible to
extract these elements from a substance.
• Boyle defined elements as simple substances
that could not be decomposed into other
substances.
Robert Boyle
(1627–1691)
Robert Boyle: Away from four
element theory
According to the phlogiston theory a colorless, odorless and
weightless substance called phlogiston, present in every material
was released while it burnt and the ‘ash’ that remained was
considered as ‘dephlogisticated’ material.
Phlogiston Theory
17 & 18th centuries
Georg Ernst Stahl
1659-1734
Johann Joachim Becher
1635 – 1682
In addition to air, earth, water and fire, the materials contain phlogiston.
NOW: Fire is a chemical reaction that converts a fuel and oxygen into
carbon dioxide and water.
What is fire?
THEN: Release of phlogiston is the definition of burning. The flame
indicates the rapid escape of phlogiston.
Questions about Combustion
• In early 18th Century, an attempt was made to
understand combustion (burning, fire).
• Why do some materials burn, while others don’t?
• When a piece of wood burned, it turned into ash
with much less mass than the original wood.
• What happens to the rest of the wood mass?
• All combustible substances contain phlogiston.
• Non-combustible substances do not contain
phlogiston.
• The more phlogiston a substance contains, the
better and more completely it burns.
• When wood burns there is a decrease in weight.
• Release of phlogiston results in weight loss.
Basics of phlogiston theory
• Air is necessary for combustion because it absorbs
the escaping phlogiston.
• The air becomes saturated with phlogiston – it
becomes phlogisticated air.
• When a candle burns in a closed jar, it burns for a
while before the flame goes out; this is because the
air in the jar is saturated with phlogiston.
• Combustion is impossible in a vacuum.
• Explanation: There was no air present to carry off
the phlogiston.
Where is phlogiston going upon burning?
Phlogiston Theory explained why things stopped
burning
Phlogiston theory of burning. (A)
When an object burns, it gives off
a substance calledphlogiston. (B)
When the space surrounding the
burning object is filled with
phlogiston, the object will no
longer be able to burn.
(A)
phlogiston
Do you support or refute the hypothesis?
Modern theory of burning
• When an object burns, it uses up a substance (oxygen) in
the surrounding space.
• When the space surrounding the burning object has too
little oxygen in it, the object will no longer be able to burn.
Metal to metal calx
(instead of wood burning, metal rusting)
• Typically, metal calx weighed more than the
original metal.
• How can this be if the calcification process
drives off the phlogiston in the metal?
• Answer: Phlogiston possesses levity; i.e., it is
lighter than nothing.
Fire to Rust: Minor hitch in the theory
Levity is an ancient idea
• Levity, or inherent lightness, is an idea found in
Aristotle.
• Air and fire rise because they possess levity, while earth
and water fall because they possess heaviness.
• These are qualitative notions. They do not fit in
quantitative, mechanist explanations.
The logic of phlogiston
https://edu.rsc.org/feature/the-logic-of-phlogiston/2000126.article
Metal calx to metal
Metal calx are powders, like ash, resulting from heating metals in a fire.
Mercury Mercury calx + phlogiston
Stahl’s idea was that phlogiston was driven out of the metal when the calx
was produced.
Mercury reacts with oxygen to form mercuric oxide
Mercury calx + Phlogiston Mercury
Charcoal
If calx is reheated in an oven filled with charcoal the calx turned back into
the original metal.
An excellent source of phlogiston is charcoal, which therefore could
reconvert a calx to its metal.
Charcoal absorbs the released oxygen and reacts to form carbon dioxide
Dephlogisticated air
• Joseph Priestley produced different gases by
performing chemical reactions and collecting the
gases produced with a pneumatic trough.
• He produced a new gas by heating mercuric calx
by concentrating the sun’s rays on it.
Joseph Priestley
1733 – 1804
Mercury calx + Phlogiston Mercury
Air
Left out air “dephlogisticated air”
No charcoal
Priestley declared: "I could not doubt but that the calx was actually
imbibing something from the air; and from its effects in making the calx
into metal, it could be no other than that to which chemists had
unanimously given the name of phlogiston."
Dephlogisticated air
Dephlogisticated air
• Mercury calx + Phlogiston Mercury
Air
• According to phlogiston theory, he was reimpregnating
the mercury calx with
phlogiston, taken from the surrounding air.
• Hence, the air that remained was deficient in
phlogiston. He called it “dephlogisticated
air”.
• Earlier charcoal was used instead of air as a
source of phlogiston.
Dephlogisticated air
• Experimenting with his new air, Priestley found that:
• A candle burned brighter in it.
• A mouse put in a closed flask of the air lived longer
than one in a flask with ordinary air.
• He tried breathing it himself, and it made him feel
great.
All air are not the same
Parallel to phlogiston theory, another concept entered chemistry
about the same time: the notion of “air” and that “air” is not just
one thing, but that there are different kinds of air (many many
air?)”
Stephen Hales
(1677 –1761)
Pneumatic troughs
Hales’s Priestly’s
New air(s)
• Joseph Black identified several
new gases, giving them names
consistent with phlogiston theory.
• “fixed air,”
carbon dioxide
• Other researchers identified other
new “airs.”
• “flammable air”
hydrogen
Joseph Black
1728-1799
Antoine Lavoisier
The Father of Modern Chemistry
1743–1794
https://www.youtube.com/watch?v=AE0
kuHKoitE
http://mysteryofmatter.net/Lavoisier.html
• Four elements theory is accepted for want of a better one.
• Boyle’s definition of element did not get accepted; so, fire, water, air and
earth are still the basic elements.
• The phlogiston theory dominated chemical philosophy.
• The composition of air and water unknown.
• Hydrogen and oxygen are yet to be discovered.
• The mechanism of respiration and metabolism understood in the context of
phlogiston.
Status of chemistry during the lifetime of Lavoisier (1743–1794)
Some materials burn because they contain phlogiston.
Phlogiston is released into the air when material burns.
Major flaw…some materials weigh more after they are
burnt.
Wood à Ashes + Phlogiston; ashes weigh less…okay…
But…Iron à Rust + Phlogiston; rust weighed more than
the iron
Lavoisier noticed the inconsistencies of the phlogiston
theory and came up with a better explanation of
combustion.
Phlogiston Theory – no longer valid!
• Established concepts as needed.
• Performed quantitative experiments to study
chemical reactions, including combustion
process.
• Built a self-financed well-equipped laboratory.
Lavoisier saw the opportunity
• Invented and invested on new instruments: a
burner that used ‘amplified Sunlight’ (heater),
calorimeter, analytical balances, etc.
Ø In 1768, at a young age of 25, he accepted office as a
Farmer–General of Taxes, and as a chemist at the Royal
Academy of Sciences, the most elite science society.
Ø Accepting Farmer-General of Taxes; he used his income to
finance his experiments.
Ø A few years later he married the daughter of another tax
farmer, Marie Anne who was only 13 at the time.
Ø Antoine Lavoisier was appointed regional inspector for the
Tobacco Commission.
Ø Lavoisier became an important landowner by successive
acquisition of land, in 1778.
Personal Life of Lavoisier
She also translated her
husband’s work from French
into English so he could share
his ideas.
Her sketching skills were
used to produce engravings
of the apparatus and methods
he used.
Marie-Anne would translate
these English papers into
French for her husband to be
able to understand them
Madam Lavoisier
Home built laboratory equipments
Helped to make sketches and take notes. She has drawn herself taking
notes at the right-hand table.
Married Marie-Anne in 1771
Lavoisier’s ideas
• Lavoisier viewed heat as one of the elements,
“caloric.”
• Air he thought was a compound of different
substances.
• He thought that Priestley’s “dephlogisticated air”
was actually an element.
Lavoisier’s classic experiment-1
• Lavoisier took mercury
and a measured volume
of air and heated them
together.
• This produced a
mercuric calx and
reduced the volume of
the air.
Lavoisier’s classic experiment-2
• He then reheated the mercuric calx by itself at a
lower temperature and saw it go back to mercury.
• In the process it produced a gas, equal in volume to
the amount lost from the first procedure.
Lavoisier’s classic experiment-3
• Observation: water is raising in the tube indicating the
amount of air decreasing as mercury goes to calx
• Lavoisier concluded that instead of the original heating
driving off phlogiston from the mercury, the mercury was
combining with some element in the air to form a compound,
which was the mercuric calx.
• He called that element “oxygen,” meaning “acid maker.”
• He classified all acids to contain oxygen; (wrong
generalization).
Oxygen displaces phlogiston
• Phlogiston theory had everything upside down.
• Instead of driving off phlogiston during combustion,
burning causes a compound to combine with the gas
oxygen.
• In the case of a metal, the compound is the calx produced
(weight increases).
• In the case of wood (rich in carbon) the weight decreases
because carbon combines with something in the air and
leaves. (Carbon plus oxygen is converted to carbon dioxide).
Oxygen vs Phlogiston
“All the facts of combustion and calcination are explained in a
much simpler and much easier way without phlogiston than
with it.
I do not expect that my ideas will be adopted at once; the human
mind inclines to one way of thinking and those who have
looked at Nature from a certain point of view during a part of
their lives adopt new ideas only with difficulty - - -.”
Lavoisier
Lavoisier announced in 1775 that he has discovered a new gas resulting upon decomposition
of Hg calx and Pb calx. He named it oxygen (meaning ‘acid maker’).
Lavoisier demonstrated (1779) its importance in respiration and glowing of candles and the
left-over part of air being toxic to animal. Thus, he established for the first time that air is
made up of two elements (one essential and another toxic for life).
Discovery of Oxygen
Carl Scheele
1742 - 1786
Swedish chemist Scheele,
identified it several years
before Priestley (1770-
1773). Unfortunately, his
scientific report sat in a
printer’s office for two
years and got published in
1777.
Priority dispute: Who discovered oxygen?
Joseph Priestley
1733 – 1804
He mentioned to
Lavoisier in 1774 about
the discovery during a
visit to Paris. Published
the results in 1775.
Antoine Lavoisier
In 1775 Lavoisier
announced to the
Academy of Science in
Paris that he had isolated
a component of air that
he called "eminently
breathable air" by
decomposition of
mercuric oxide.
1743—1794
Carl Scheele
1742 - 1786
A great chemist,
discovered 7 elements.
Slow in publishing results.
Who discovered oxygen?
Do you really need three?
Joseph Priestley
1733 – 1804
Furious free thinker and
scholar. Published every
observation. His mind was
inflexible with respect to
phlogiston.
Antoine Lavoisier
Brilliant economist,
great and meticulous
scientist. Mind was
flexible to discard old
ideas. Lacked
professional integrity.
1743—1794
On an evening in October 1774, Antoine Lavoisier, the
architect of the chemical revolution, learned that the
Unitarian English minister, Joseph Priestley, had made a
new gas. Within a week, a letter came to Lavoisier from
the Swedish apothecary, Carl Wilhelm Scheele,
instructing the French scientist how one might synthesize
this key element, the life-giver oxygen.
Scheele’s work was carried out years before but
remained unpublished until 1777. Scheele and Priestley
fit their discovery into an entirely wrong logical
framework—the phlogiston theory—that Lavoisier is
about to demolish. How does Lavoisier deal with the
Priestley and Scheele discoveries? Does he give the
discoverers their due credit? And what is discovery after
all? Does it matter if you do not fully understand what
you have found? Or if you do not let the world know?
A popular Broadway play
The Law of Conservation of Matter
By paying close attention to the weights of his experimental
ingredients, Lavoisier made the Conservation of Matter a
fundamental principle of chemistry.
The Law of Conservation of Mass
Total mass is the same
(Reactants) (Products)
Magnesium + oxygen = magnesium oxide
Explain how the experiment in
this picture demonstrates the Law
of Conservation of Mass.
Air is not an element but a mixture.
• Lavoisier was sure that air contained more than one element.
• Determined the amount of the “reacting component” in the air. He named this
reacting component oxygen.
What is an element?
Robert Boyle’s (1627-1691) definition of element
“An element is a substance that cannot be decomposed into
anything simpler”
Cavendish: “When inflammable and common air are
exploded in a proper proportion, almost all the inflammable
air, and near one-fifth of the common air, lose their
elasticity, and are condensed into dew (water).” (Done in
1781 and Published in 1784).
Water is not an element. It is a mixture.
Lavoisier (1783)
• Combustion of inflammable air with oxygen carried out in
a closed vessel yielded water in a very pure state.
• Water can be decomposed to inflammable air (hydrogen)
and oxygen. Iron filings in water rusted and released
inflammable air. Rusting occurred through the reaction of
released oxygen with iron filings.
• Thus, water can be decomposed to two elements and can
also be formed from the same two elements. Water is not
an element, it is a compound.
Water and air are not elements: Four element theory is not valid
Lavoisier: “There was no principle of scientific conduct that forbade him to
give better explanations of other men's discoveries than those they could
provide themselves, an attitude to which no man of science could take
exception.
This theory is not, as I hear it called, the theory of the French chemists. It is
mine. It is a right that I claim by the Judgment of my contemporaries and at
the bar of history.”
Cavendish’s experiments were done in 1781 and published in 1784. In the
meantime, his assistant Blagden visited Paris in 1783 and mentioned about
Cavendish’s results to Lavoisier. The latter published the water results in
1783. There was some feeling that Lavoisier might have used the information
given to him by Blagden to anticipate the publication of a discovery made by
Cavendish.
Priority disputes and Lavoisier’s reaction
Lavoisier recognized the opportunity
“The importance of the end in view prompted me to
undertake all this work, which seemed to me destined to
bring about a revolution in . . . chemistry. An immense
series of experiments remains to be made.”
Lavoisier, Lab Notebook entry dated Feb. 20, 1773
30 yrs old
Law of the conservation of Mass
Law of the indestructibility of matter
applied to chemical change
In every operation an equal quantity
of matter exists both before and after
operation.
Antoine Lavoisier
1789
Established a system of nomenclature
Conceived oxygen-based acid principle
Established the field of thermochemistry
Order in chaos
• French chemist, 1700s
• Father of modern
chemistry
• Developed methods for
precise measurements
• Discovered law of
Conservation of Mass,
proved matter could not be
created, destroyed
• Recognized, named oxygen,
introduced metric system
• invented first periodic
table
Antoine-Laurent Lavoisier
(1743–1794)
• Irish chemist, 1600s
• Father of modern
chemistry
• First to define element
• The Sceptical Chemist,
1661, described matter as
cluster of tiny particles
(now called atoms)
• Changes in matter
occurred when clusters
rearranged
• Boyle’s law - temperature,
volume, pressure affect
gases
Robert Boyle
(1627–1691)
Chemistry
"It took them only an instant to cut off that head, and a hundred
years may not produce another like it."
Joseph-Louis Lagrange
Despite his eminence and his services to science and France, he came under attack
as a former farmer-general of taxes and was guillotined in 1794 (51 yrs old).
Marie had spent her teen years studying chemistry and learning to read
English. She also learned art from the revolutionary painter David. As Roald
Hoffmann traces old records, he finds Marie managing the schedule of her
husband's laboratory and creating fine detailed drawings of apparatus. She
receives no credit, ----- Was she the perfect secretary or a scientific
collaborator?
Marie-Anne Paulze
Lavoisier
Antoine Lavoisier – Sad Ending
A landmark portrait presents a
modern, scientifically minded couple
in fashionable but simple dress, their
bodies casually intertwined. Antoine
Laurent Lavoisier is often referred to
as the “father of modern chemistry”
and Marie Anne Lavoisier is known
as a key collaborator in his
experiments—aspects of the couple’s
personality that have been well
served by this famous image.
(Marie Anne Pierrette Paulze, 1758–1836)
MET, NewYork Collection
Priestley fled
to the U.S.
• Priestley was an enthusiastic supporter of the American and
French revolutions. His outspoken radical views enraged a mob
that burned down his house and library. Priestley escaped to the
United States where he lived for the remainder of his life.
Antoine Lavoisier, Douglas McKie, 1952
An International Historic Chemical Landmark, The
Chemical Revolution, ACS, pamphlet, 1999
Antoine Lavoisier, H. Hartley, Proc. Royal Soc. A, 189,
427-454, 1947
http://mysteryofmatter.net/Lavoisier.html
Readings
“Well, certainly, Lavoisier was one of the great, great
masters of all time.”
Humphry Davy