Topic 3 Chemistry During the European Renaissance

The renaissance took place during 1400 - 1600 and accelerated the Roman’s and the Greek’s knowledge.

Figure 3.1: Some Famous Icons of the Renaissance

The renaissance also challenged and improved upon “old knowledge”.

3.1 Notable Figures and Works in the Renaissance

3.1.1 Paracelsus

Figure 3.2: Painting of Paracelsus

Philippus Aureolus Theophrastus Bombastus von Hohenheim (otherwise known as “Paracelsus”) was a famous Roman physician who not only rejected the classical Greeks’ “four humors” medical theory, but also rejected Aristotle’s four element model and modified Geber’s mercury and sulfur theory.

He was responsible for the creation of the Tria Prima and was also responsible for the rise of iatrochemistry: the application of alchemy to medicine.

3.1.1.1 Tria Prima

Figure 3.3: Paracelsus’ Tria Prima

Like previously mentioned, Paracelsus’ Tria Prima expanded upon Geber’s mercury and sulfur theory by introducing salt to the theory.

His work also delved into broad principles as opposed to specific substances. For instance…

1. Sulfur \(\rightarrow\) inflammability
2. Mercury \(\rightarrow\) fusability, volatility
3. Salt \(\rightarrow\) incombustability, non-volatility

As an example, when wood burns, one might conclude the following using Paracelsus’ Tria Prima:

1. Smoke \(\rightarrow\) mercury
2. Fire and light \(\rightarrow\) sulfur
3. Ash \(\rightarrow\) salt

3.1.1.2 Iatrochemistry

Iatrochemistry was the old term for medicinal chemistry (iatro meaning “medical” or “doctor” in Greek).

Traditionally, Galen believed that diseases were caused by an imbalance in the body’s four humors: yellow bile, black bile, phlegm, and blood. Hence, it is necessary to balance the four humors (via herbal and complex medicine) to achieve health.

However, Paracelsus sought specific cures (i.e., inorganic salts) for specific ailments that were relatively simpler to describe.

Figure 3.4: An Iatrochemistry Textbook

Like the one shown in figure 3.4, Iatrochemistry lead to lots of people writing textbooks. Hence, iatrochemistry was more open than transmutation alchemy.

3.1.2 Psuedoscience versus science

One tends to associate alchemy (i.e., seeking immortality and / or transmutations) with non-scientific connotations and modern chemistry with scientific connotations.

What makes a science a science is how it is practiced: the Scientific method.

3.1.2.1 Scientific method

Figure 3.5: Francis Bacon’s Scientific Method

Francis Bacon was an English philosopher, a politician, and a scientist.

Figure 3.6: Painting of Francis Bacon

Bacon also laid out the motivation and the philosophy of the scientific method.

3.1.3 Jan Baptist van Helmont

He was a Flemish (present day Belgium) iatrochemist.

Figure 3.7: Painting of Helmont

van Helmont’s theory suggested that there were two ultimate elements: air and water. Moreover, air does not take part in transmutations; water can be molded into different materials.

“The first beginnings of bodies, and of corporeal causes, are two, and no more. They are surely the elements water, from which bodies are fashioned, and the ferment.”

– van Helmont himself

Like the above quoteblock suggests, “ferment” molds the various forms and properties of materials.

van Helmont also demonstrated the scientific experiment via his willow tree experiment.

3.1.3.1 van Helmont’s willow tree experiment

Figure 3.8: van Helmont’s Willow Tree Experiment

van Helmont wrote the following about his willow tree experiment:

“I took an earthen pot and in it placed 200 pounds of earth which had been dried out in an oven. This I moistened with rain water, and in it placed a shoot of willow which weighed five pounds. When five years had passed the tree which grew from it weighed 169 pounds and about three ounces. The earthen pot was wetted whenever it was necessary with rain or distilled water only. It was very large, and was sunk in the ground, and had a tin plated iron lid with many holes punched in it, which covered the edge of the pot to keep air-borne dust from mixing with the earth. I did not keep track of the weight of the leaves which fell in each of the four autumns. Finally, I dried out the earth in the pot once more, and found the same 200 pounds, less about 2 ounces. Thus, 164 ounces of wood, bark, and roots had arisen from water alone.”

– Ortus Medicine, 1648

Granted - we now know this to be false as van Helmont did not take air (i.e., CO₂) into account. However, van Helmont did illustrate several features of the scientific method:

1. Designing an experiment to test a hypothesis.
2. Belief in the conservation of matter.
3. His controlled experiments used distiled water.

3.1.3.2 van Helmont’s “chaos”

van Helmont was the first to coin the word “gas”: Greek for chaos.

28 kg of charcoal was heated to yield 2.2 kg of ash. According to van Helmont, the rest of the charcoal left as “wild spirit” or spiritus sylvester. However, when the charcoal was heated in a sealed container, the charcoal would either not burn or result in a violent explosion where the “spirit” would escape:

“Suppose thou, that 62 pounds of Oaken coal, one pound of ashes is composed: Therefore the 61 remaining pounds are the”wild spirit" which, also being fired, cannot depart, the Vessel being shut. I call this spirit, unknown hitherto, the new name of “gas”, which can neither be retained in Vessels nor reduced to a visible form, unless the seed is first extinguished."

– Physick Refined, English Language edition, 1662

Since van Helmont did not believe that air was an ingredient involved in transmutation reactions, he thought that air is a gas that is devoid of “ferment”.

3.1.4 Ortus medicine

Figure 3.9: A Snapshot of the Ortus

3.2 Development of Chemistry: Age of Reason

This took place from the 1600s to the 1700s. This period was also the period of modern science and philosophy. Institutions like the Royal Society also originated then

Figure 3.10: Famous Figures of the Age of Reason

Scientific methods were also established as ways to gain knowledge of the natural world!

Figure 3.11: Early Physics and Biology

Figure 3.11 shows early publications on Biology and Physics.

3.2.1 Science during an epidemic

England was in the midst of a bubonic plague epidemic from 1665 to 1667. The disease is carried by fleas (i.e., Xenopsylla cheopis) that have been infected with the Yersinia pestis bacterium - the causative agent of the bubonic plague.

Figure 3.12: The Flea and the Bacterium that Causes Bubonic Plague

From the summer of 1665 to 1667, Newton was studying in Cambridge and self-quarantined in his home in Lincolnshire, England.

“In those days I was in the prime of my age for invention & minded Mathematicks & Philosophy more than at any time since.”

– Issac Newton himself

During the summers, Newton made full use of his time and developed the ideas that he would now be most famous for! His famous “apple” incident was likely what inspired the laws of universal gravity; he also performed various optical experiments throughout his house and in 1666, invented Calculus.

Newton returned to Cambridge in 1667 and in 1669, was appointed the Lucasian chair of Mathematics.

3.2.2 Robert Boyle

Figure 3.13: Painting of Robert Boyle

Robert Boyle was an Irish aristocrat who lived from 1627 - 1691. He was the 7^th son and the 14^th child of Richard Boyle, the first earl of Cork. Boyle used his family’s wealth to fund his own research.

Nonetheless, Boyle bought Chemistry into mainstream 17^th - 18^th century natural philosophy. However, Boyle is often associated with the development and the establishment of the scientific method in Chemistry. He subjected claims to Bacon’s scientific method.

3.2.2.1 Critiquing Aristotle’s, Paracelsus’, and van Helmont’s chemistry

“As for the greene sticke the fire dos not separate it into elements, but into mixed bodies, disguised into other shapes: the Flame seems to be but the sulphurous part of the body kindled; the water, boyling out at the ends, is far from being elementary water, holding much of the salt and vertu of the concrete: and therefore the ebullient juice of several plants isby physitians found effectual against several distempers, in which simple water is altogether unavailable. The smoake is so far from being aire, that it is as yet a very mixt body, by distillation yielding an oile, which leaves an earthe behind it; that it abounds in salt, may appear by its aptness to fertilise land, and by its bitterness, and by its making the eyes water (which the smoake of common water will not doe) and beyond all dispute, by the pure salt that may be easilty extracted from it, of which I lately made some, exceeding white, volatile and penetrant…”

– Boyle’s argument against statment X

Boyle first asked what an element was. From this, Boyle ultimately concluded that Aristotle’s four “elements”, Paracelsus’ Tria Prima, and von Helmont’s “air” and “water” are not elements.

Figure 3.14: Robert Boyle’s Sceptical Chymist

Boyle used experimental methods to show the fallacy of all three theories; he even went as far as to question the soundness of fire analysis (i.e., using fire to “break down” materials to their “elements”).

3.2.2.1.1 Boyle’s hypothesis of an element

“I now mean by elements, as those chymists that speak plainest do by their principles, certain primitive and simple, or perfectly unmingled bodies; which not being made of any other bodies, or of one another, are the ingredients of which all those called perfectly mixt bodies are immediately compounded, and into which they are ultimately resolved.”

– Appendix of 2^nd ed., The Sceptical Chymist

The irony was that Boyle did not find the above quoteblock to be very important only until later!

3.2.2.2 Corpuscular theory of matter

“It seems not absurd to conceive that at the first Production of mixt Bodies, the Universal Matter whereof they among other Parts of the Universe consisted, was actually divided into little Particles of several sizes and shapes variously mov’d”

– Sceptical Chymist

This theory was heavily influenced by Pierre Gassendi (1592 - 1655) and stated that all matter is made up of corpuscles: invisible and untouchable discrete units (not quite like atoms). Corpuscles also do not bother to differentiate between our modern notion of atoms and molecules.

Furthermore, the shape, the size, the texture, the motion, and the interactions between corpuscles determined how these corpuscles formed and what properties they had - for instance, the sweetness of sugar, the roundness of a sugar corpuscle, and the corrosiveness and the sharp-tasting nature of acids.

However, the aforementioned is still too general: there really wasn’t any exact mechanisms for interactions. The capabilities to find the mechanisms were far beyond the scope of experimental capabilities at the time!

3.2.2.3 Boyle’s gas law

His gas law stated that:

\[\begin{equation} P = \frac{1}{V} \end{equation}\]

Boyle experimentally found that at a fixed temperature, the pressure of a fixed amount of gas increases inversely proportionally to the volume that it occupies.

3.3 Phlogiston Theory

Figure 3.15: Combustion and Rusting of Iron

This section focuses on how scientists during the 17^th to the 18^th century explained the reactions shown in figure 3.15

3.3.1 Terra pinguis

Figure 3.16: Black and White Photo of Johann Joachim Becher

Becher (1635 - 1682) was a German physician, alchemist, iatrochemist, businessman, and an entrepreneur who believed that earth, water, and air mixed to form organic matter and minerals.

According to Becher himself, he believed that there were three types of earth:

1. Terra fluida (i.e., mercurious earth)

   This made substances fluid, volatile, and was also responsible for substances’ metallicity.

2. Terra lapidea (i.e., vitreous earth)

   This was responsible for fusing substances together - this earth was responsible for the principle of fusability.

3. Terra pinguis (i.e., fatty earth)

   This was a kind of earth that produced oily sulfur and had combustible properties.

3.3.2 Georg Stahl

Figure 3.17: Picture of Georg Stahl

Stahl (1660 - 1734) was a German professor of medicine at the university of Halle who developed and utilized Becher’s original principles and ideas to explain different phenomenons and observations. Stahl also noted that combustion, calcination, and rusting were all similar in nature, and not only used phlogiston theory to attempt to explain them, but also to explain plant growth.

Figure 3.18: Combustion and Metallurgy as Explained by Phlogiston Theory

Although Stahl was wrong in the end, this was an example of “science” being practiced.

3.3.3 Burning candles and plant growth?

Interestingly, phlogiston theory also explained why candles in burning jars would eventually go out:

Figure 3.19: A Candle Going Out in Phlogiston Theory

When a candle burns, it gives off phlogistons that the air in the jar absorbs. However, when the air is saturated with phlogistons (i.e., phlogisticated air) and can no longer absorb any more phlogistons, the candle is then extinguished.

Yet, wouldn’t the atmosphere be saturated with phlogistons one day (and hence, no combustion can occur when this happens)?

Figure 3.20: Plant Growth in Phlogiston Theory

According to phlogiston theory, plants grow and absorb phlogistons: this also explains why charcoal is phlogiston rich. The theory also gave way to the idea that the atmosphere is involved in the growth of plants, hence laying the groundwork for photosynthesis in the future!

3.3.4 Criticism and popularity of the theory

The following statement (taken directly from the lecture slides) summed up everything wrong with the theory:

Wood loses weight when it burns, while metal gains weight when they are burned to form stix.

Yet, the theory was still popular for the following reasons:

1. Some scientists concluded that phlogistons had negative mass.
2. The “conservation of mass” idea was not very well accepted or even known.
3. Experiments performed then were not very conclusive that there was a real loss in weight in real life.

The theory was eventually demolished by Lavoisier’s work in the 1770s and became increasingly problematic from the 1750s when better techniques and methods were developed to understand the hcemistry of gases.

3.4 Pneumatic Chemistry

Figure 3.21: Famous Icons During the Age of Enlightenment

During this time, the success of natural philosophy caused others to break free from tradition, tyranny, religion, and superstition.

The study of air and gases belongs to Physics; however, methods had not yet been developed to trap and quantitatively measure gases. Form the 1700s onwards, experimental techniques like the Pneumatic Trough allowed air to be studied in a more quantitative measure.

It was through the pneumatic chemists that the chemical revolution by Lavoisier took place in the 1770s to the 1780s.

3.4.1 Pneumatic trough

Figure 3.22: Portrait of Stephen Hales

Stephen Hales (1677 - 1761) was an English clergyman, botanist, and a chemist whose magnum opus Vegetable Staticks (1727) talked about plant physiology, including but not limited to the following topics:

Figure 3.23: A Page of *Vegetable Staticks

1. Root pressure
2. Transpiration
3. Speculation of light in plant growth
4. Experiments on how air enters and leaves plants

3.4.1.1 The trough itself

Figure 3.24: The Pneumatric Trough from Vegetable Staticks

The pneumatic trough was an apparatus to collect air after a reaction happened. After its invention, the trough became a standard piece of laboratory equipment.

3.4.2 Fixed air

Figure 3.25: Portrait of Joseph Black

Joseph Black (1728 - 1799) was a Scottish physician and a chemist who discovered latent heat in 1761. He observed that when heat was applied to ice, it melted, yet the temperature of the ice did not melt.

Figure 3.26: Black’s Analytical Balance

The analytical balance was a light-weight beam balanced on a knife-edge fulcrum. Its accuracy was 1 part out of 250; its basic designed was unchaged until the advent of the digital analytical balance in the later parts of the 20^th century.

The device was also crucial in Black’s discovery of CO₂.

3.4.2.1 CO₂

Black himself was intrigued about finding cures for bladder stones. At the time, alkalis were known to dissolve bladder stones (though too strong an alkali can potentially kill the patient).

Figure 3.27: A Reaction of Magnesium Alba

Black studied magnesium carbonate (i.e., MgCO₃). He initially believed the CO₂ evolved from the above reaction be “fixed air”. He later then discovered that other processes like respiration, fermentation, and combustion also produced this “fixed air”.

3.4.2.1.1 Did Black actually achieve what he set out to do?

He did not!

However, Black used his analytical balanced to measure the mass of the magnesium alba before and after heating. He concluded that the weight of fixed air and residue equaled to the original mass of the magnesium alba. This experiment was also evidence for the conservation of mass principle.

3.5 De-Phlogisticated Air

Figure 3.28: Portrait of Joseph Priestley

Priestley (1733 - 1804) was an English clergyman, philosopher, chemist, and an educator who went to the US later in life due to his political views.

He discovered more than 20 kinds of air: NH₃, HCl, CO, SO₂, N₂O, NO, and O₂ just to name a few!

Figure 3.29: Soda Water and Priestley’s Pneumatic Trough

Priestley is also credited with the invention of soda water!

3.5.1 Priestley’s experiments

Figure 3.30: Pristley’s Jar Experiments

When the candle was still burning, the mouse was well and alive. However, after the candle stopped burning, the mouse became unconcious.

Yet, when a plant was placed into the jar, the mouse and the candle continued to live and burn.

The conclusion? Animal respiration, like candle burning, releases phlogiston. The plant then absorbs phlogiston and this leads to an ever sustaining cycle of absorbing and releasing phlogiston (hence affirming Stahl’s phlogiston theory).

3.5.2 Priestely’s mercury oxide

In 1774, Priestely made oxygen by heating mercuric oxide (i.e., HgO) floating on the surface of some mercury in an inverted phial.

Figure 3.31: Priestely’s Heating Mechanism

The resultant air from the above apparatus, when used in his jar experiment, allowed the mouse in the jar to live far longer than if the mouse were to be placed in atmospheric air.

Yet, some argue that even though Priestely isolated oxygen, he did not manage to discover oxygen as his interpretation of the gas was wrong from the start!

3.5.3 Carl Wilhelm Scheele

Figure 3.32: Bust of Scheele Engraved into a Coin

He was a scientist who performed experiments that led to the isolation of dephlogisticated air.

Figure 3.33: Scheele’s Results

However, Scheele did not publish his results until 1777!

3.6 Inflammable Air and Water

3.6.1 Henry Cavendish

Figure 3.34: Portrait of Henry Cavendish

Henry lived from 1731 - 1810 and he was an English physicist, chemist, aristocrat, and one of England’s wealthiest people (he became that way from inheriting a fortune from his father - a superb experimentalist).

While Henry made incredibly accurate experiments, he was also extremely shy!

Figure 3.35: The Famous Cavendish Experiment

His famous Cavendish experiment was made to measure the gravitational constant \(g\)!

3.6.2 Inflammatory air

First, Henry placed zinc, tin, or iron in a salt spirit (i.e., HCl) or acid of vitriol (i.e., H₂SO₄)

Figure 3.36: Inflammatory Air Production in Henry’s Own Words

Henry found that given a fixed amount of metal, that a fixed amount of inflammable air would be produced regardless of the acid’s concentration.

Hence, Henry concluded that this “inflammatory gas” comes from the metal and speculated that this inflammatory gas was phlogiston.

3.6.3 Water

Priestely noted that when inflammable burned together with dephlogisticated air, that water is produced. He also noted that water is produced when inflammable air burns together with atmospheric air.

However, Cavendish made quantitative measurements of this phenomenon:

Figure 3.37: Cavendish’s Observations of Water Production from Air Combustion

In his experiments, Cavendish burned about two parts of inflammable air with five parts of normal air and noticed that all the inflammable air and about a fifth of the normal air was gone - a dew also formed on the insides of the vessel that he was conducting the experiment on!

From this, Cavendish concluded that normal air was a mixture of four parts phlogisticated air to one part dephlogisticated air and two volumes of inflammable air reacted with one volume of dephlogisticated air.

Cavendish’s experiments implicitly assume the conservation of mass and matter!

3.7 Antoine Lavoisier

Figure 3.38: Painting of Lavoisier and His Wife

Lavoisier was a French chemist, tax farmer, and an aristocrat who used his wealth to fund his scientific experiments.

Lavoisier was probably the most important chemist in history, yet he was guillotined in the French revolution.

3.7.1 Lavoisier on phlogiston theory

By the 1770s, instruments and experiments had became increasingly quantitative to the point that when metal burned, it could be easily found that it gained mass.

Lavoisier even went as far as to burn sulfur and phosphorus - he also convinced himself that these products gain weight.

In 1772, Lavoisier speculated that the gain in mass was due to “air” being incorporated into the metal during roasting. The “air” therefore had “air matter”, heat, and / or light particles. However, what kind of “air” was being added (perhaps Black’s fixed air)?

3.7.2 Priestly and Lavoisier

“The principle which unites with metals during calcination, which increases their weight and which is a constituent part of the calx is: nothing else than the healthiest and purest of air which after entering into combination with a metal, can be set free again; and emerge in an eminently respirable condition, more suited than atmospheric air to support ignition and combustion”.

– Antoine Lavoisier, 1777

During 1774 - 1775, Priestly came to Paris and dined with Lavoisier.

Figure 3.39: Lavoisier’s Realized Reaction

It was during then that Lavoisier pieced together the jigsaw pieces and realized the above reaction!

3.7.3 Oxygen

Figure 3.40: Lavoisier Performing Experiments on Respiration

By 1779, Lavoisier had shown that all acids that included sulfur, carbon, nitrogen, and phosphorus had the same “dephlogisticated air” (even though he was not aware of other acids like HF, HCl, and HBr at the time).

Hence, he named the air oxygen: “oxys” meaning sharp and “gonos” meaning producer.

Figure 3.41: Reference Equations According to Three Interpretations of Chemistry

3.7.4 Lavoisier’s interpretation of water

In 1783, Cavendish’s assistant visited Lavoisier and told him about Cavendish’s experiment. However, Lavoisier was already convinced that phlogiston was not necessary; he then concluded that water is a compound fashioned from hydrogen and oxygen, re-naming “inflammable air” as hydrogen in the process.

Figure 3.42: A Gasometer in the Late 1700s

A gasometer is a device that is able to continuously deliver gas and measure the volume of gas that has been introduced into a reaction. Lavoisier needed two of these instruments: one to measure the volume of hydrogen and another to measure the volume of oxygen.

Each gasometer would cost about 250000 USD today - they were about two meters high, made from high-quality brass, and used in public demonstrations.

3.8 Overturning Phlogiston Theory

“…Chemist have made phlogiston a vague principle, which is not strictly defined, and which consequently fits all the explanations demanded of it. Sometimes it has weight, sometimes it has not; sometimes it is free fire, sometimes, it is fire combined with earth; sometimes it passes through the pores of vessels, sometimes they are impenetrable to it. It explains at once causticity and non-causticity, transparency and opacity, colour and the absence of colours. It is a veritable Proteus that changes its form every instant!…”

– Antoine Lavoisier

Lavoisier was ready to overturn phlogiston theory in 1785. He proposed two different substances: caloric (i.e., heat) and light. These substances were weightless and Lavoisier aimed to do experiments with them.

3.8.1 Caloric

With Laplace’s help, Lavoisier invented the ice calorimeter (that used Black’s discovery latent heat).

Figure 3.43: An Ice Calorimeter

For a chemical reaction or a biological process that was performed in the inner chamber of the above figure, the ice would melt and it could be collected and measured.

However, one would require thermodynamics principle that wasn’t present during Lavoisier’s era lest the interpretation of data would be tough!

Yet, the quantification of caloric gave chemistry a quantitative and a rigorous direction.

3.8.2 A new chemical language

Figure 3.44: Lavoisier’s Work on a New Chemical Nomenclature

Lavoisier’s new chemical nomenclature was influenced by Linnaeus’ naming system in Biology. The new nomenclature (that we now use) is made up of two parts and was also much more concise. Lavoisier and his colleagues thought that correct language was essential for reasoning and hence, to turn chemistry into a rigorous science.

3.8.3 Traité Élémentaire de Chimie

This book was also Lavoisier’s magnum opus.

Figure 3.45: Lavoisier’s Magnum Opus

In this work, Lavoisier also mentioned the principle of the conservation of mass (that had widely come to be accepted and became the foundation of all of Lavoisier’s experiments and theory).

“…We may lay it down as an incontestable axiom, that, in all the operations of arts and nature, nothing is created: an equal quantity of matter exists both before and after the experiment; the quantity and quality of the elements remain precisely the same; and nothing takes place beyond changes and modifications in the combination of these elements. Upon this principle the whole art of performing chemical experiments depends.”

– Lavoisier on his Magnum Opus

This was the first ever modern chemistry textbook that included the following topics (not limited to):

1. Discovery of oxygen
2. Composition of water
3. Theory of combustion based on oxygen
4. Analysis of oxides and of acids
5. Salt formation from acidic and metallic oxides
6. Chemical instrumentations and practical chemistry

3.8.3.1 Definition of an element

“All that can be said upon the number and nature of elements is, in my opinion, confined to discussions entirely of a metaphysical nature. The subject only furnishes us with indefinite problems, which may be solved in a thousand different ways, not one of which, in all probability, is consistent with nature. I shall therefore only add upon this subject, that if, by the term elements, we mean to express those simple and indivisible atoms of which matter is composed, it is extremely probable we know nothing at all about them; but, if we apply the term elements, or principles of bodies, to express our idea of the last point which analysis is capable of reaching, we must admit, as elements, all the substances into which we are capable, by any means, to reduce bodies by decomposition. Not that we are entitled to affirm, that these substances we consider as simple may not be compounded of two, or even of a greater number of principles; but, since these principles cannot be separated, or rather since we have not hitherto discovered the means of separating them, they act with regard to us as simple substances, and we ought never to suppose them compounded until experiment and observation has proved them to be so.”

– Antoine Lavoisier

Lavoisier’s Traité Élémentaire de Chimie also contained Lavoisier’s working definition of an element.

Figure 3.46: Lavoisier’s 33 Original Elements

An element would no longer be defined as metaphysical entities, but will be based on experiments. In his magnum opus, Lavoisier lists 33 elements along with two forms of energy: heat and light that are grouped together with oxygen, hydrogen, and nitrogen.

His original elements were as follows:

1. 3 non-metals, 3 chlorine compounds, flourine, boron, and 17 metals with their old names.
2. 5 oxides of calcium, magnesium, barium, aluminum, and silicon.

Lavoisier did not include any alkalis, soda, or potassium salts. Lavoisier believed that the aforementioned could be decomposed to something simpler.

3.8.4 Lavoisier’s death during the revolution

Figure 3.47: Modern Day Impression of the French Revolution

On July 14^th, 1789, the people of France rose up, eventually overthrowing their king and demolishing the aristocracy.

During the so-called “reign of terror”, up to 40000 people were executed, many by a new invention: the guillotine. In May 6, 1794, Lavoisier was guillotined as he was a tax farmer.

When Napolean came to power in 1799, the anarchy ended, by which time France was at war with the whole of Europe.