concluded that commercial iron contain carbon, which gives rise to carbon dioxide
on combustion, thus explaining Priestley’s observations [18]. In another letter,
Scheele criticised Landriani’s view that all acids owed their acidity to carbon
dioxide [19]. As long as he could not prepare other acids from carbon dioxide,
Scheele could not accept this theory. In the same letter, Scheele elaborated his view
on Kirwan’s experiments with carbon dioxide and iron. This caused Kirwan to
respond: [20]
The reason, why the red, by it self calcined, mercury [HgO] give fixed air [CO 2 ] by
distillation with iron, is because the mercury calx [HgO] much easier deprive iron of its
combustible [i.e. phlogiston], than the dephlogisticated air [O 2 ], which is combined with it
in the fixed air.
Graphite (writing lead) did not give carbon dioxide with mercury(II) oxide
according to Kirwan. This is true, but the reason is that mercury oxide decomposes
to mercury and oxygen at lower temperature than would be required for the reaction
with graphite to occur. Scheele found other reports on carbon dioxide in the literature that he did not believe; he could experimentally refute a report that carbon
dioxide arise from distillation of lead amalgam or from nitrogen oxide (saltpetre air)
and oxygen [21].
Bergman openly supported Kirwan’s view in 1784, saying that he valued
Kirwan’s papers very high, and that he had reasons to favour Kirwan’s views over
Scheele’s [22]. Thus, Bergman and Scheele did not always agree, and it is thus not
fair to call Bergman the theoretician with Scheele merely performing his experiments. Scheele was truly an individual thinker and occasionally, such as in this
case, Scheele who was closer to the truth.
18.3 Bergman and the Aerial Acid
Bergman had been investigating the presence of an acid in the atmosphere since at
least 1769; in a paper published in spring 1773, he wrote that he had exposed a
sample of pure alkali to the ambient atmosphere on an attic for 4 years. His original
objective may have been to disprove Wallerius claim that air contains sulphuric
acid (Sect. 9.6). By 1772, he had proved experimentally that carbon dioxide is an
acid, and communicated these results in a letter to Priestley [23]. Priestley attributed
the discovery of the acidic properties to Bergman [24]. In fact, both Black, [2] and
especially Cavendish, [25] had found that carbon dioxide (fixed air) reacts with
bases, but they did not explicitly state that carbon dioxide is an acid. Bergman did
not refer to the works of Black or Cavendish in his paper, which irritated Thomson
when he wrote his History of Chemistry [26]. As Bergman developed an interest in
mineral waters (Chap. 17) about the same time, he had another strong reason to
investigate the properties of carbon dioxide.
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18 Research on Carbon Dioxide
on combustion, thus explaining Priestley’s observations [18]. In another letter,
Scheele criticised Landriani’s view that all acids owed their acidity to carbon
dioxide [19]. As long as he could not prepare other acids from carbon dioxide,
Scheele could not accept this theory. In the same letter, Scheele elaborated his view
on Kirwan’s experiments with carbon dioxide and iron. This caused Kirwan to
respond: [20]
The reason, why the red, by it self calcined, mercury [HgO] give fixed air [CO 2 ] by
distillation with iron, is because the mercury calx [HgO] much easier deprive iron of its
combustible [i.e. phlogiston], than the dephlogisticated air [O 2 ], which is combined with it
in the fixed air.
Graphite (writing lead) did not give carbon dioxide with mercury(II) oxide
according to Kirwan. This is true, but the reason is that mercury oxide decomposes
to mercury and oxygen at lower temperature than would be required for the reaction
with graphite to occur. Scheele found other reports on carbon dioxide in the literature that he did not believe; he could experimentally refute a report that carbon
dioxide arise from distillation of lead amalgam or from nitrogen oxide (saltpetre air)
and oxygen [21].
Bergman openly supported Kirwan’s view in 1784, saying that he valued
Kirwan’s papers very high, and that he had reasons to favour Kirwan’s views over
Scheele’s [22]. Thus, Bergman and Scheele did not always agree, and it is thus not
fair to call Bergman the theoretician with Scheele merely performing his experiments. Scheele was truly an individual thinker and occasionally, such as in this
case, Scheele who was closer to the truth.
18.3 Bergman and the Aerial Acid
Bergman had been investigating the presence of an acid in the atmosphere since at
least 1769; in a paper published in spring 1773, he wrote that he had exposed a
sample of pure alkali to the ambient atmosphere on an attic for 4 years. His original
objective may have been to disprove Wallerius claim that air contains sulphuric
acid (Sect. 9.6). By 1772, he had proved experimentally that carbon dioxide is an
acid, and communicated these results in a letter to Priestley [23]. Priestley attributed
the discovery of the acidic properties to Bergman [24]. In fact, both Black, [2] and
especially Cavendish, [25] had found that carbon dioxide (fixed air) reacts with
bases, but they did not explicitly state that carbon dioxide is an acid. Bergman did
not refer to the works of Black or Cavendish in his paper, which irritated Thomson
when he wrote his History of Chemistry [26]. As Bergman developed an interest in
mineral waters (Chap. 17) about the same time, he had another strong reason to
investigate the properties of carbon dioxide.
248
18 Research on Carbon Dioxide