Say physics
and Isaac Newton comes to mind. Say biology,
and Charles Darwin comes to mind. Who comes to mind, if you say Chemistry?
To me, it used to be Dmitri Mendeleev.
Nowadays, it is Antoine Lavoisier.
Lavoisier changed human understanding of
nature as fundamentally as, if not more than, Newton and Darwin. But he seems
far less known than the other two. Chemistry in general, seems less glamourous
than Physics or Biology. It was not always so.
Alchemy
After he discovered Gravity, the Three
Laws of Motion, invented Calculus and wrote a book on Optics, Isaac Newton
spent several years of his life experimenting with Alchemy. One of the goals
alchemists in those days, was to discover a way to turn ordinary metals like
lead, iron or copper into gold. Europe was full of superstitious legends of
great alchemists in India and Arabia who knew such secrets in the past, and
some European alchemists tried to rediscover such things. One of the Europe’s
legendary wizards of earlier centuries, had apparently discovered something
called the Philosopher’s Stone, which could alchemically turn lead into gold
and also made its owner immortal. His name was Nicholas Flamel, which should be
familiar to anyone who read the first Harry Potter book, called, Harry Potter and the Philospher’s Stone.
Flamel, Newton and another legend, Leonardo da Vinci, feature in yet another
best selling novel of recent times, Dan Brown’s The da Vinci Code, as members of the Priory of Sion.
In such romantic times was Antoine Lavoisier
born, to an aristocratic family in France, in 1743, a few years after Newton’s
death. Newton failed dismally as an alchemist.
Four Elements and Phlogistons
The standard belief in Europe was that
all substances in Nature were made of four elements – Air, Water, Fire and
Earth. In fact, this was common belief among all the major civilizations from
time immemorial – India, China, Arabia, Persia, Greece, Egypt. In India, a
Fifth element called Aakasha, along with these four Vaayu (Air), Aapa or Jala
(Water), Agni (Fire) and Prithvi (Earth) was believe to be the five basic
Elements : the Pancha Bhoothas. European Alchemy was an offshoot of Arab
experiments and science, centered around Baghdad in the 8th and 9th
centuries. Al-chemy, Al-kali, Al-gebra, are words of Arabic origin, which are
now part of the scientific vocabulary in European languages.
But around the same time that Newton was
figuring out gravity and the laws of motion, a German scientist, Johann Becker,
suggested that flammable substances had inside them a substance called
phlogiston, which enabled them to burn.
This conjecture quickly became accepted among all scientists, though
nobody could prove the existence of a phlogiston.
Experiments with Air
About a century later, a Scottish professor, Joseph Black, found
from experiments that when limestone is heated or mixed with acids, it releases
a type of air, which would not support flame. This air, which Black called
“fixed air”, would also dissolve in certain liquids. Black soon discovered that fixed air was also
produced by respiration and fermentation. In 1766, Henry Cavendish isolated inflammable air, produced by the action
of dilute acid on metals. In 1772 Daniel Rutherford showed that removal of
fixed air from air depleted by respiration or combustion left a new type, noxious air.
A few years later, an English scientist,
Joseph Priestley, performed some marvelous experiments, and discovered seven
new “airs”. But they continued to
believe that Air was a fundamental element.
It’s important to understand the
historical significance and originality of these experiments. People across different
cultures have known that water comes as fresh or salt water, but understood that
salt is merely dissolved in water. Though air surrounds us, neither the
Egyptians who built the pyramids, nor Indians who composed Vedas and built
Buddhist stupas and Hindu temples, nor the Chinese or Greeks or Sumerians ever experimented
with Air or tried to understand it. These experiments of the late eighteenth
century were momentous and unprecedented.
Priestley put a candle in a closed glass
jar, and noticed that its flame died after a particular amount of time. He put
a mouse in a closed glass jar and noticed, that it also died after some time. From
these experiments, Priestley concluded that both the candle and the mouse used
up some part of the air, which he called dephlogitsicated
air.
Priestley tried another experiment where
he put a plant in a jar, and a lighted candle. Much to his surprise, the candle
burnt longer than it did normally
before it went out! After a while, the burnt candle could be relit and it would
burn again. Priestley suspected that plants somehow produce dephlogicticated
air. When atmostpheric air was deprived of dephlogisticated air, it left behind
what he called phlogisticated air, which was unfit to support flame or animal
respiration. Priestley seems to have done these experiements before 1772, as he
mentions in his book Experiments and 1774 book Observations of Different Kinds of Air.
Priestley did not work in isolation. He
quotes several other scientists researching the composition of air, namely Dr
Hales, Dr Brownrigg, Mr Lane and Mr Cavendish.
The Polymath Lavoisier
Meanwhile in France, Antoine Lavoisier also experimented with air.
Lavoisier came from a wealthy aristocratic family and studied Law, even though
he was more interested in science. In his time,in France, Law was prestigious,
similar to the prestige of engineering or medicine in India, in recent decades.
But Lavoisier was an energetic and curious student – while studying Law, he
also studied geology, physics, astronomy, mathematics, botany and anatomy! From
Nicolas Louis de Lasaille, an astronomer who sailed and mapped the southern
skies, he learnt mathematics. The rigor and clarity of mathematics, and their
absence in chemistry which he simultaneously learnt, troubled Lavoisier. From
Lasaille he learnt the value of instruments and their accuracy.
Lavoisier also learnt physics from Abbe Jean Antoine Nollet, a
marvelous lecturer and public demonstrator. Nollet advocated a view of
scientists as a Republic, with an obligation to serve the public good, besides
exploring the unknown. These and Nollet’s avid experimentation, were ideas and
values that heavily influenced Lavoisier.
Bernard de Jessieu taught Lavoisier about the world of plants, and
they wandered around Paris on botanical collecting expeditions. Jean Etienne
Guettard taught him geology; the analysis of minerals and waters were the
foundations of Lavoisier’s experiments in chemistry. The French Government
appointed Guettard and Lavoisier to conduct a Geological Survey of France.
In 1773 Lavoisier explained his experiments on fixation of Air at
the Royal Academy of France. Lavoisier was assisted by Pierre-Simon Laplace, a
brilliant mathematician. Meticulous measurement and superior instrumentation,
lessons he learned from Lasaille, marked his experiments.
Lavoisier started with one big idea –
that the fixation of air converted flammable substances into acids. His early
experiments showed that when phosphorus or sulphur were burnt, they absorbed
some part of the air and turned into phosphoric and sulphuric acids,
respectively. He didn’t burn them in the open, but in closed jars – and he
measured not just the weight of the air before and after burning (combustion),
he measured the weights of the flammable phosphorus or sulphur and the acids
they produced. He noticed that the weight of the air lost during combustion
equalled the increase in weight between material and its acid.
He then experimented by burning metals
like lead and tin. This produced a substance called calx – and this burning of
metals was called calcination. Calcination also caused a gain in weight. This phenomenon
puzzled Lavoisier deeply – it is obvious to all that burning is a destructive
process. How could a destructive process increase
weight?
It October 1774 Priestley visited Paris,
met Lavoisier, they conducted some experiments together, and no doubt had wonderful
conversations with each other. But Priestley like every other chemist of his
time firmly believed in the phlogiston theory, which said that flammable
substances emitted these phlogistons. Lavoisier, decided that phlogistons no
longer made sense. Far from losing phlogistons, all burning substances seemed
to be gaining something –they were absorbing dephlogisticated air (which
Lavoisier called vital air).
Lavoisier offered this new hypothesis – that
combustion was a process that involved the absorption of dephlogisticated air. Since
dephlogisticated air generated acids
(which was called oxys in French),
he renamed it Oxygen. And he called
his hypothesis the Oxygen Principle.
Meanwhile in England, Cavendish had
discovered with another experiment, that dephlogisticated air combined with
flammable air in a closed glass jar, mysteriously, some dewdrops appeared on
the inner surface of the jar. It turned out to be water. Lavoisier repeated
this experiment with similar results, but no longer troubled by phlogistons, he
concluded that water itself is a combination of these two airs. Since flammable
air generated water (hydro in Latin), he called it Hydrogen.
Lavoisier had proved that three of the old
elements – Air, Water and Fire, were not Elements at all. Fire is the addition
of oxygen to flammable substances. Air consisted of different substances, which
were perhaps truly more basic. And Water consisted of two types of Air – Oxygen
and Hydrogen.
Lavoisier had killed Alchemy, and in its
place developed Chemistry.
He had repeated the experiments of
others before him Priestley (and Carl Wilhelm Scheele), Cavendish, Joseph Black
– the discoverers of Oxygen Hydrogen and
Carbon-di-oxide - and explained them better than the discoverers.
Cavendish was the first of the English
scientists to follow Lavoisier, in rejecting the phlogiston theory and
accepting his Oxygen principle. Priestley stubbornly refused to abandon
phlogistons – he wrote a book in 1794, compiling his Lectures on Experimental Philosophy particularly including Chemistry.
Lavoisier meanwhile had launched another
program to develop a new vocabulary for chemistry. And published a book in 1787
Methode de Nomenclature Chimique (Method of Chemical Nomenclature). In the
succeeding century, several new elements were discovered, showing that fourth
Old Element, Earth, was far more complicated than the other three Old Elements.
An Anglo American bias
I studied in schools in Madras, India, where
the language of study was English, in the 1970s and 1980s. English has the been
the dominant language in colleges since the 1850s when the British first
established Presidency Colleges and Universities in the three Presidency cities
– Madras, Calcutta and Bombay. But most Indian schools used to teach in Indian
languages. This situation changed rapidly. Sometime during the 1980s, English
became the preferred language in most urban schools. In the 2000s, English
began to replace local languages as the meidum, mostly in the Southern states –
Tamilnadu, Kerala, Andhra Pradesh and
Karnataka. This is now spreading to other states of India too. I studied my own
mother tongue Tamil, as a second language, and for a few years, Hindi, as a
third language. What does this have to with Physics or Chemistry?
Note that the first two scientists I
mentioned in my opening paragraph are English, by language and nationality. The
others are not; but they are European. While my school education exposed me to
history and fiction and culture from various parts of the world, the science
was exclusively European. What I didn’t realize then, was that the bias was
strongly English, not just European. It
continues to be biased thus, even though we have Indians, not Englishmen,
setting the syllabus. The stories of Newton’s apple and James Watt brewing tea,
don’t have equivalents for French or German or Swedish scientists. The global ignorance
of non-European scientists is nothing less than academic apartheid.
The world should celebrate Lavoisier.
References
1. Vital
Forces by Graeme Hunter
2. Elements
of Chemistry by Antoine
Lavoisier
3. Lectures
on Experimental Philosophy particularly including Chemistry by Joseph Priestley
4. Lives
and Times of Great Pioneers
by CNR Rao, Indumati Rao
7. Wikipedia on Cavendish
8. The
Invention of Air by
Steven Johnson
Some hopefully relevant links
