Henry Cavendish and The Revolutionary Discovery of Hydrogen

Henry Cavendish was the first to isolate and identify one of the most important elements in modern chemistry.
Trevor English

The original discoverer of inflammable air, otherwise known as hydrogen, was notoriously shy and hid from public view; yet he was an incredibly influential chemist.

Notably, this renowned researcher worked heavily in the research and study of various gases and calculated the density and the mass of the Earth in an experiment known as the Cavendish experiment.

Where it all began for Cavendish

Born in 1731, he quickly rose to be one of the top chemists of his time. Born in Nice, he was born to a family of aristocratic roots. He grew up largely without a mother as she passed away during the childbirth of his brother when Henry was the age of two. 

At the age of 11, Cavendish started attending a private school in London and later went on to attend the University of Cambridge. 


 Never getting a degree, however, Cavendish would go on to work with the Royal Society of London. He was elected to a few different roles within the Royal Society that he did not take very seriously, but rather put his efforts and expertise into the use of scientific instruments within the society. It was this work that led him to write his first paper, named Factitious Airs.

Cavendish would go on to work with a man by the name of Charles Blagden, who aided Cavendish in entering London's scientific society. This friendship and partnership worked well as Blagden served as a representative of Cavendish who was often too shy to speak in front of crowds or committees. Cavendish was able to achieve a significant amount in his research during his work with Blagden, specifically in the fields of mechanics, magnetism, and optics. 

While he had a variety of interest areas in his research, like many 18th century researchers, he focused primarily on a field known as pneumatic chemistry. It was in this research work that he made one of the largest discoveries of his time.

The discovery of hydrogen

In 1766, Cavendish was investigating doubts by top minds of the time that water and oxygen were the only basic elements. While doing experiments, he isolated hydrogen and identified it as a unique element. The scientific understanding of gasses at the time was primitive, and Cavendish referred to two types of air, known as fixed air and flammable air.

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Fixed air as carbon dioxide and flammable air as hydrogen. 

Hydrogen was highly flammable, leading him to refer to the gas as "inflammable air". Upon discovery, he even guessed that the molecules of hydrogen were proportioned two to one in water, which we now understand as H20.

If you want to take a look at the specific experiments undertaken by Henry Cavendish to discover hydrogen, the BBC has an amazing segment recreating them with the renowned Brian Cox.


It should be noted, Cavendish's discovery of hydrogen was simply the first time that the gas he isolated was recognized as a unique element. Hydrogen gas was first created by Robert Boyle and others many years earlier, but they failed to recognize this flammable gas as its own element. 

In the late 1800s, scientists believed that there was an element in the air called phlogiston. It's a now-defunct theory, but it stated that elements that had phlogiston in it were flammable. Upon the combustion process, the phlogiston was released and the element burned could be considered dephlogisticated. 

Cavendish's other work with air

Tying back to the gasses that Cavendish was working with, he also discovered that the air that was a result of respiration was non-phlogisticated, or in other words, it was fixed air, carbon dioxide. 

Cavendish was able to isolate and produce carbon dioxide, collecting each of the unique gases he studied in bottles. For his work on "air", he was awarded the Royal Society's Copley Medal. 

A significant amount of Cavendish's discovery and work on gases was the essential precursor of the chemical revolution brought about by Antoine-Laurent Lavoisier years later. 

During his work with hydrogen, Cavendish also determined that the burning of hydrogen actually created water. This experiment simply found that water was condensed from the air through the burning of hydrogen.

By 1785, Cavendish had well made a name for himself and began investigating other properties of air. Specifically, Henry Cavendish was one of the first scientists to determine the specific ratio of nitrogen and oxygen in atmospheric air, being one part oxygen to 4 parts nitrogen.

Calling back to our discussion of phlogiston oriented chemistry, if you read any of Cavendish's works and papers, you'll notice everything is written in this phrasing. It wasn't until 1787 that Cavendish converted away from the phlogiston theory, one of the first people outside of the scientific hub of France to do so. 


At the end of the day, Cavendish was a reclusive scientific mind who only tended to socialize with those in the scientific community with himself. His partnership with Blagden served him well over the years, allowing him to take a more focused role in science with less of a responsibility to maintain public opinion. 

His work on air and gases came at a crucial period where gas chemistry was just starting to accelerate. His work on hydrogen specifically meant too that he is the father of one of the most foundational elements to modern chemistry. 

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