Daniel Rutherford

  Daniel Rutherford (3 November 1749 – 15 November 1819) was a Scottish chemist and physician who was most famous for the isolation of nitrogen in 1772.

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Daniel Rutherford was born in Edinburgh and was educated at the University of Edinburgh where his father John Rutherford (1695–1779) was a professor of medicine. As a student, he isolated nitrogen in 1772 and described oxygen, or “vital air” as he called it, in 1778.

In 1786, he was appointed Regius Professor of Botany in Edinburgh and as Keeper of the Royal Botanic Garden Edinburgh, after the death of Professor John Hope (1725–86). Rutherford held these posts until his death. His daughter Margaret married James Haldane and he was also a maternal uncle of Sir Walter Scott.

Isolation of Nitrogen

When Joseph Black was studying the properties of carbon dioxide, he found that a candle would not burn in it. When a candle was burned in a closed container of air, the candle would go out eventually, and the remaining air would not support a flame. This was normal, but when the carbon dioxide (caused by the candle) was absorbed by chemicals, some air was not absorbed. The air that remained did not support a flame.

He turned this problem over to his student at the time, Daniel Rutherford. Rutherford kept a mouse in a space with a confined quality of air until it died. Then, he burned a candle in the remaining air until it went out. Afterwards, he burned phosphorus in that, until it would not burn. Then the air was passed through a carbon dioxide absorbing solution. The remaining air did not support combustion, and a mouse could not live in it.

Rutherford called the gas (which we now know would have consisted primarily of nitrogen) “noxious air” or “phlogisticated air”.

Rutherford reported the experiment in 1772. He and Black were convinced of the validity of the phlogiston theory, so they explained their results in terms of the theory. They said that as mice breathed and combustion was created, phlogiston was given off and entered the air, along with the carbon dioxide. When the carbon dioxide was later absorbed, the air still contained phlogiston. In fact, the air was saturated with it. That was why candles and other objects would not burn in it.

Rutherford believed that, in like manner, a living creature gives up phlogiston while breathing and when placed in air that is already saturated with phlogiston, can no longer breathe and must die.