Nitrogen is the chemical element with the symbol N and atomic number 7, existing primarily as a colorless, odorless, and largely unreactive gas. It makes up about 78% of Earth’s atmosphere, representing the largest component of the air we breathe. The history of its isolation and identification is often confused because several scientists were working on the same problem simultaneously. This article clarifies the circumstances of its official discovery and the scientist credited with its isolation.
The Search for Different Airs
The middle of the eighteenth century marked a period of intense focus on the composition of air, as chemists began classifying gases, which they collectively referred to as “airs.” The prevailing scientific explanation was the Phlogiston Theory, which proposed that flammable materials released phlogiston during burning. Scientists were distinguishing between “fixed air” (carbon dioxide) and “vital air” (oxygen). This framework directed research toward understanding why combustion ceased in a closed vessel, suggesting the air had become saturated with phlogiston. The ultimate goal was to separate the atmosphere into its component parts to understand the residual fraction remaining after the active components were consumed.
Daniel Rutherford’s Isolation Method
The credit for the first clear isolation and description of this residual gas belongs to Daniel Rutherford, a Scottish physician and student of Joseph Black. Rutherford formalized his findings in his 1772 doctoral dissertation at the University of Edinburgh. His experiment focused on systematically removing the known active components from a confined volume of air.
Rutherford first used a mouse or a burning candle to consume the “vital air” (oxygen) in a sealed container, noting that respiration and combustion would eventually stop. This process produced carbon dioxide, which was then removed by passing the remaining air through an alkali solution, such as potash. The gas that remained after this two-step purification process could not support combustion or life. Rutherford called this inert residue “noxious air” or “phlogisticated air,” believing it to be common air saturated with phlogiston that prevented further burning. This methodology provided the first definitive characterization of the gas we now call nitrogen.
Parallel Observations by Other Scientists
The discovery of nitrogen is often debated because several other scientists made near-simultaneous observations of this same residual air. Joseph Priestley, an English theologian, isolated what he called “burnt air,” but his primary focus was on “dephlogisticated air” (oxygen), and he often misidentified the inert component. English scientist Henry Cavendish also performed experiments in 1772 that produced the gas, noting that a portion of the air remained after combustion and absorption of carbon dioxide. Swedish pharmacist Carl Wilhelm Scheele independently isolated this atmospheric residue around the same time. While these scientists encountered and isolated the gas, Rutherford is generally credited because he was the first to clearly define and publish the distinct, non-combustible, and non-life-supporting properties of this specific residual component in his thesis.
The Naming of Nitrogen
Following Rutherford’s work, the gas was initially known by descriptive names based on its properties, such as “noxious air” or “phlogisticated air.” French chemist Antoine Lavoisier proposed the name azote, derived from the Greek word azotikos, meaning “no life.” Lavoisier chose this name because the gas could not support respiration or combustion; the term azote is still used in French and several other Romance languages today.
The English name “nitrogen” was later proposed by French chemist Jean-Antoine-Claude Chaptal in 1790. This name was constructed from the Greek words nitron and genes, meaning “nitre-forming.” The change was prompted by the discovery that the element was a component of nitric acid and involved in the formation of saltpeter (potassium nitrate, or nitre). This new name reflected the element’s chemical reactivity and helped transition its classification from an inert atmospheric residue to a fundamental element.