Saturday, 20 August 2016

The origin of Modern Chemistry

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
5.     Wikipedia on Lavoisier 
6.     Wikipedia on Priestley 
7.     Wikipedia on Cavendish 
8.     The Invention of Air by Steven Johnson

Some hopefully relevant links
1.     Insulin Man – Fred Sanger
2.     CNR Rao on GN Lewis 
3.     The Alchemy of Air - Haber and Bosch 
5.     Non-European scientists : What did Brahmagupta accomplish?


3 comments:

  1. Lavoisier was caught up in the French Revolution and had a grisly end. In the power struggle between Jacobins and Montagnards, he was seen siding with Montagnards, Jacobins were the authors of Terror in Paris. He tried to escape from Jacobins' clutches, he was caught and guillotined.

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  2. One reason why Indian scientists of yore don't find a mention is that Indian culture did not give predominance to individuals and events in individual life. That is why so many Hindu scientists, technocrats and even literary authors with exceptions remain anonymous. WE have no idea of the designers or Chief Engineers of famous temples or even the ambassadors or naval captains of Chola period.

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    Replies
    1. // Indian culture did not give predominance to individuals and events in individual life //

      Kings, poets, religious leaders, petty chiefs, devadasis, some generals, some ministers, and the occasional businessman have been mentioned in literature.

      Chalukya temples and some temples in Tamilnadu have inscriptions of sthapathis and silpis and other people, but not in other regions, that I know of.

      Systematic history has not been a strong point of Indians.

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