Priestly had discovered what he called “dephlogisticated air,” and which was later named by Antoine Lavoisier as Oxygen. (Image: Shutterstock)
Exactly 247 years ago, on August 1, 1774, a man in his early 40s was in his lab ready to continue a series of experiments to understand the nature of air. But today’s experiment was special in a way that the curious rebel had no idea. Through today’s experiment, nature was going to reveal one of its fundamental truths to a man whose name was Joseph Priestly.
Over the past experiments, Joseph Priestly was looking for different ‘airs’ and trying to observe their properties. In one of the experiments, he noticed that when a burning candle was placed in a jar, it was put out. In such a jar, a mouse would also die because of the lack of air. However, putting a green plant in the same jar and exposing it to sunlight would bring the air back, which would permit the flame to burn and the mouse to breathe.
On August 1, Priestly took a lump of reddish solid substance, which was mercury oxide, and put it inside an inverted container, which was placed in a pool of mercury. Then he took a ‘burning lens’ and focussed the sunlight on the reddish lump hoping the substance to burn and collect the air that was produced.
The produced ‘air,’ he wrote, was “five or six times as good as common air,” and it allowed the mouse to breathe and the candle to burn for four times longer than earlier. Priestly had discovered what he called “dephlogisticated air,” and which was later named by Antoine Lavoisier as Oxygen.
The discovery proved to be a crucial clue for Lavoiser to develop his revolutionary theory of chemical reactions.
orn in England in 1933, Priestly had to leave the country because of his strong and unorthodox opinions on religion and politics. On February 6, 1804, after dictating a few changes in one of his manuscripts to one of his sons and an assistant, he said, “That is right. I have now done,” and died painlessly in a few minutes.
Priestley’s discovery broke the notion that air was an indestructible elemental component and paved the way for modern chemistry.