Antoine Lavoisier: carbon cycle pioneer

Written by: Simon Mitton


Hello and welcome to my blog on “deep carbon science” –– a fascinating research field in the geosciences. My history of deep carbon science gives lively accounts of 150 scientists who contributed to the development of this new field over a period of four centuries. I write history by telling stories about interesting people. Here’s an extract from my account of the research of the great chemist Antoine-Laurent de Lavoisier (1743–1794).

At the end of the eighteenth century, the quest to understand how living organisms interact with atmospheric gases dominated the research frontier of carbon science in France. Understanding the science that linked coal, life, and the carbon cycle, was central to Lavoisier’s work on what we know as Earth’s carbon cycle. In 1774 he noted that the respiration of animals (breathing) and combustion were processes that produced carbon dioxide in the atmosphere. That intriguing thought, connecting the phenomenon of life to the element carbon called for experiments!

During the 1780s Lavoisier conducted several precise experiments to gauge the heat produced by burning a piece of charcoal, and by a guinea pig in a bell-jar. His most famous of these took place in 1784. He used a human “guinea pig,” his young assistant Armand Séguin (1764–1835), who breathed oxygen through a facemask while Lavoisier measured increases in his breathing rate and pulse. From these trials, Lavoisier became convinced that respiration is slow-burn combustion, a chemical reaction that required an input of oxygen and produced an output of carbon dioxide, accompanied by the generation of heat energy.

Lavoisier reflected on this in the context of comfort of public the stuffy theatres in Paris which he frequented. At the Palais des Tuileries, following a theatrical performance, he found that oxygen in the upper part of the room was reduced while carbon dioxide increased. He concluded that all of the oxygen in the theatre would have been exhausted within four and a half hours in the absence of replacement air from outside. That reasoning led to an imaginative speculation: a guinea pig in a bell-jar perishes within an hour, humans would suffocate in a few hours in an airtight room … and yet, after untold millions of years, plants and animals have not yet exhausted the vitality of the atmosphere. What could this mean?

In 1792 he conjectured that plants probably possessed “the means nature uses to maintain the respirability of air” on a global scale. In his final paper on the properties of carbonate rocks and coal, penned the year before he was guillotined on 8 May 1794 after a show trial, Lavoisier applied quantitative reasoning to the global transfer of carbon by natural processes:

We can conceive what immense quantity of carbon is sequestered in the womb of the Earth, since marbles, limestones and calcareous earths contain about 3/10th and sometimes 1/3 of their weight in fixed air, and this latter is composed for 28/100th of its weight of carbon; then, it is easy to conclude that the calcareous rocks contain 8 to 9 pounds of carbon by quintal.

In a geochemical aside, he remarked that there could be no doubt that elemental carbon “is part in a number of combinations in the three kingdoms – minerals, plants and animals”, although he did not outline the changes in the form carbon must takes to pass from the mineral (coal) to the plant and animal kingdoms.

Read more … Simon Mitton, From Crust to Core (9781108426695), 106–110

Next blog … [coming soon] Marie Tharp (1920–2006) pioneer cartographer of the ocean floor whose discoveries was “discounted as girl talk.”

From Crust to Core:
A Chronicle of Deep Carbon Science,
Simon Mitton

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About the Author: Simon Mitton


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