Lavoisier was a French chemist who was a key figure in the chemical revolution of the 18th-century. Amongst his pioneering achievements, he recognised and discovered oxygen and hydrogen – discovering the role of oxygen in combustion. Lavoisier helped bring a new scientific rigour to the subject of chemistry, using quantitative methods rather than relying on hypothesis. He constructed a list of elements and helped to construct the metric system. Using the work of other scientists, Lavoisier was able to combine into a new common framework which broke with previous classical beliefs. He ushered in a new era of modern chemistry.
Lavoisier was a wealthy French noble who used his position in the Ferme Generale to fund both his chemistry experiments and social works. Despite his efforts in the field of water sanitation, agriculture and street lighting, his position in the hated Ferme Generale made him a target during the French Revolution, and in 1794 he was guillotined for ‘tax fraud and selling adulterated tobacco.’ A year later he was exonerated.
Lavoisier was born in a noble French family in Paris on 26 August 1743. His mother died when he was just five years old, but this left him very rich as he inherited her wealth. He studied at the College des Quatre-Nations, University of Paris and became interested in the sciences chemistry, botany, astronomy and mathematics. After college, he studied for his law degree, but despite being admitted to the bar, never practised as a lawyer.
Lavoisier was more interested in pursuing his interest in chemistry, geology and the natural sciences. He was influenced by the ideals of the French Enlightenment. His interest in chemistry was influenced by Etienne Condillac. Lavoisier was also concerned with issues of social welfare. He used his fortune and time to consider some of the pressing social issues of the time. In 1765, he wrote an essay on the problem of street lighting which received the attention and praise of the king. In 1768, he proposed an aqueduct to bring clean water to the citizens of Paris. When this was not built, he switched to investigations into whether the water could be purified – something that was relevant to his chemistry knowledge.
Lavoisier also made contributions to suggesting improving the hygiene of prisons and the effect of gun powder on air quality. In 1772, he prepared a study on how to improve the air flow for the Hotel-Dieu hospital when it was rebuilt.
Lavoisier also bought a share in the Ferme generale. This organisation collected tax on behalf of the king – and was widely hated for its power and abuses in collecting taxes. Lavoisier commissioned the building of a wall around Paris to help the collection of customs taxes entering the city.
In 1771, he married Marie-Anne Pierrette Paulze, who was just 13 at the time, but another member of the nobility. Despite her young age, she came to play an important role in his scientific career, translating many English scientific documents into French. She also helped his work in the laboratory.
An important business for the Ferme Generale was its monopoly on the distribution of tobacco. Lavoisier devised a method for improving the quality of tobacco and detecting adulteration. He enforced higher standards for tobacco and stopped many from adultering its composition. However, he became unpopular with many tobacco retailers and this would be used against him during the French Revolution.
During the revolution, Lavoisier helped fund a patriotic Republican paper run by Pierre S. DuPont, and in 1791 he chaired a commission on the introduction of a new metric system. However, he was later removed on political grounds due to a groundswell of opposition to the former nobility. As the French Revolution gained momentum, there was an increasing persecution of those associated with the old regime. On 24 November 1793, he was arrested with many other tax farmers and were accused of defrauding the government and adultering tobacco. After a summary trial, Lavoisier and 22 co-defendants were sentenced to death by guillotine.
Work as a chemist
In 1772, Lavoisier experimented with the burning of substances. He found burning phosphorus and sulphur led to an increase in their weight – something he attributed to ‘metallic calces’. He also repeated previous experiments of other scientists such as Joseph Black on burning alkalies, such as chalk and quicklime. Lavoisier frequently repeated experiments of other scientists (not always with proper attribution). This gave him a wide understanding of different chemistry experiments. He often came to different conclusions to the original scientists.
In 1774, Lavoisier continued experiments on lead and tin. Lavoisier undertook these experiments in sealed containers. He deduced from the experiments that the increase in weight of the metals was due to a combination with atmospheric air. In this year, he met with English scientist Joseph Priestley, who was visiting Paris. Priestly had isolated oxygen – something he termed ‘dephlogisticated air.’ or an especially pure form of air.
This meeting encouraged Lavoisier to further investigate this property. He found that Mercury calx gave off this ‘pure air’ which supported respiration and combustion. He would later term this element oxygen from the Greek words meaning “acid former.” Lavoisier also gave term hydrogen – from the Greek ‘water former’. In an experiment he was able to make water from burning jets of hydrogen and oxygen – this was the first proof that water was not a basic element, but actually composed of two gases. He would also show that this element oxygen was used in respiration and heat was generated by animals who breathed in this air.
An important contribution to the science of chemistry was Lavoisier’s careful experiments which introduced a new quantitative rigour into the experiments.
“We must trust to nothing but facts: These are presented to us by Nature, and cannot deceive. We ought, in every instance, to submit our reasoning to the test of experiment, and never to search for truth but by the natural road of experiment and observation. “
Elements of Chemistry (1790)
He developed his own gasometer which could weigh gases and elements to a fine level of detail. He later made cheaper versions available to other chemists. With this device, he carefully weighed products in sealed gases so that no gases could escape. This led him to the important observation that although matter can change its state in a chemical reaction – nothing is lost or gained. Net weight remains the same. In other words, matter merely changes form. This is sometimes referred to as Lavoisier’s Law which is often paraphrased as: “Rien ne se perd, rien ne se crée, tout se transforme.” (“Nothing is lost, nothing is created, everything is transformed.”)
“We may lay it down as an incontestible axiom, that, in all the operations of art and nature, nothing is created; an equal quantity of matter exists both before and after the experiment; the quality and quantity of the elements remain precisely the same; and nothing takes place beyond changes and modifications in the combination of these elements.”
Antoine Lavoisier, Elements of Chemistry (1790) p. 226
Another pioneering development of chemistry was the development of a new way of classifying chemical elements. Up until that time, elements had been lumped into very broad categories, which had changed little since the time of Aristotle – these were earth, air, fire and water. However, Lavoisier was acutely aware of the grave limitations of this. Together with other scientists, he developed a list of 55 substances which could not be decomposed into simpler elements. These elements included the gases of oxygen, nitrogen and hydrogen. It also included acids, alkalies and organic acids.
Lavoisier’s quantification and the law of conservation of matter was controversial as it challenged existing orthodox beliefs of other scientists. Whilst not disputing his experiments, other scientists disputed his reasoning. However, Lavoisier’s methods and new ideas of practising chemistry spread rapidly.
In 1789, he published Traité élémentaire de Chimie (Elementary Treatise on Chemistry), this used his new chemistry terminology and can be considered the first chemistry textbook. It was translated into English and although the older generation of scientists rejected some of its conclusions, it became a standard port of reference for future generations of chemists.
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