Priestley studied the physiological effects of oxygen, and found that breathing
oxygen was particularly easy: “Who can tell but that, in time, this pure air may
become a fashionable article in luxury. Hitherto only two mice and myself have had
the privilege of breathing it” [62]. Here, Priestley was obviously wrong, as Scheele,
unknown to him, also was breathing pure oxygen in Sweden. Priestley added a
caution:
But, perhaps, we may also infer from these experiments, that though pure dephlogisticated
air might be very useful as a medicine, it might not be so proper for us in the usual healthy
state of the body: for, as a candle burns out much faster in dephlogisticated than in common
air, so we might, as may be said, live out too fast, and the animal powers be too soon
exhausted in this pure kind of air. A moralist, at least, may say, that the air which nature has
provided for us is as good as we deserve [63]
21.7 The Discovery of Nitrogen
The discovery of nitrogen is usually attributed to a student of Joseph Black, Daniel
Rutherford (1749–1819), who became a professor of botany in Edinburgh in 1786.
In his doctoral thesis presented in 1772, he described an experiment where he left a
mouse in a closed vessel until it died [64, 65]. A candle was then burnt in the
remaining air until the flame went out. Rutherford then burnt phosphorus in the
remaining air until the flame went out. He finally absorbed the carbon dioxide with
alkali. Rutherford did not, however, give this gas a name, nor did he realise that it
was a component in ordinary air. Scheele obtained pure nitrogen by heating
ammonium chloride and manganese(IV) oxide before 1774, but he did not realise
its identity with atmospheric nitrogen that he was studying about the same time
[66].
21.8 Lavoisier and the Chemical Revolution
Our modern conception of chemical elements was introduced by the French chemist
Antoine Lavoisier (1743–1794; Fig. 21.7). Formally, Lavoisier had a degree in law,
but never practised as a lawyer. Among other official duties, he was responsible for
inspecting the quality of gunpowder production in Paris, and his chemical research
was conducted in his spare time. He got up at 5 a.m. every morning and spent three
morning hours in his laboratory, and returned to the laboratory for three hours after
concluding his official duties at 7 p.m.
In notes made in February 1772, Lavoisier expressed his intention to study air
and carbon dioxide (fixed air) and on September 10, he described his first experiments on the weight increase of burning phosphorus. He found that when phosphorus or sulphur burned in closed vessels, the weight of the air in the vessel
decreased. More importantly, he found that the phosphorus and sulphur increased in
21.6 Priestley’s Theories of Oxygen and Combustion
295
oxygen was particularly easy: “Who can tell but that, in time, this pure air may
become a fashionable article in luxury. Hitherto only two mice and myself have had
the privilege of breathing it” [62]. Here, Priestley was obviously wrong, as Scheele,
unknown to him, also was breathing pure oxygen in Sweden. Priestley added a
caution:
But, perhaps, we may also infer from these experiments, that though pure dephlogisticated
air might be very useful as a medicine, it might not be so proper for us in the usual healthy
state of the body: for, as a candle burns out much faster in dephlogisticated than in common
air, so we might, as may be said, live out too fast, and the animal powers be too soon
exhausted in this pure kind of air. A moralist, at least, may say, that the air which nature has
provided for us is as good as we deserve [63]
21.7 The Discovery of Nitrogen
The discovery of nitrogen is usually attributed to a student of Joseph Black, Daniel
Rutherford (1749–1819), who became a professor of botany in Edinburgh in 1786.
In his doctoral thesis presented in 1772, he described an experiment where he left a
mouse in a closed vessel until it died [64, 65]. A candle was then burnt in the
remaining air until the flame went out. Rutherford then burnt phosphorus in the
remaining air until the flame went out. He finally absorbed the carbon dioxide with
alkali. Rutherford did not, however, give this gas a name, nor did he realise that it
was a component in ordinary air. Scheele obtained pure nitrogen by heating
ammonium chloride and manganese(IV) oxide before 1774, but he did not realise
its identity with atmospheric nitrogen that he was studying about the same time
[66].
21.8 Lavoisier and the Chemical Revolution
Our modern conception of chemical elements was introduced by the French chemist
Antoine Lavoisier (1743–1794; Fig. 21.7). Formally, Lavoisier had a degree in law,
but never practised as a lawyer. Among other official duties, he was responsible for
inspecting the quality of gunpowder production in Paris, and his chemical research
was conducted in his spare time. He got up at 5 a.m. every morning and spent three
morning hours in his laboratory, and returned to the laboratory for three hours after
concluding his official duties at 7 p.m.
In notes made in February 1772, Lavoisier expressed his intention to study air
and carbon dioxide (fixed air) and on September 10, he described his first experiments on the weight increase of burning phosphorus. He found that when phosphorus or sulphur burned in closed vessels, the weight of the air in the vessel
decreased. More importantly, he found that the phosphorus and sulphur increased in
21.6 Priestley’s Theories of Oxygen and Combustion
295