conclusions were disproved by Uno Boklund [46]. Grimaux concluded that if
Lavoisier had carried out Scheele’s experiment, Scheele would have been the
discoverer of oxygen. This implies that Scheele could predict that heating silver
calx would give rise to a previously unknown gas. Instead, Boklund concludes that
Grimaux attempted to establish Lavoisier as an independent discoverer of oxygen.
In reality, Scheele’s letter (dated September 30) may, along with Priestley’s visit in
October, have been two factors putting Lavoisier on the right track.
According to Scheele, “the phlogiston is a true element and completely simple
principle” [47]. It could be transferred between bodies, but “phlogiston can
impossibly be obtained on its own”. It should be recalled that Scheele had talked
about hydrogen gas as “elastic phlogiston” in the late 1760s. Scheele also spoke
vaguely about the effect of phlogiston on atoms (or particles as Scheele wrote): by
the action of the heat that occupied the voids between atoms, it could cause a
material to melt or to turn into a gas.
6 Phlogiston could also put the particles in such
a situation that they absorbed all incoming light rays, or just a few. Thus, Scheele
attributed colour to the interactions between light and atoms under the influence of
phlogiston. In fact, oxidation/reduction have profound effect on light absorption and
colour, both in organic compounds, where, i.e. reduction of conjugated p-systems
blue-shifts the absorption, and in d-metal ions, which typically have very different
colours in different oxidation states.
Bergman gave a definition of phlogiston in his Instructions to Lectures in
Chemistry in 1779 (Sect. 11.2): [48] “The reason for such a nature [i.e. combustibility] lies actually in a very fine matter, which the ancients called Phlogiston.
It is so subtle that, on its own, it escapes all our senses but can still be moved from
one body to another according to the laws of affinity”. Here, Bergman does not
explicitly state that phlogiston cannot be isolated. Bergman wrote that phlogiston is
probably a constituent of all matter, but in order to render a substance combustible,
a large excess of loosely bound phlogiston is needed.
Bergman accepted Scheele’s view on oxygen and combustion, and wrote in the
second edition of his paper on elective attractions:
The third system [of explaining the nature of heat] is that of my sagacious friend
Mr. Scheele, who thinks that the matter of heat is not simple, but compounded of phlogiston and vital air [oxygen], closely combined, and that light consists of the matter of heat,
with an excess of phlogiston. His Treatise on Air and Fire will best show how he arrived at
these conclusions. This hypothesis is not without its difficulties, which I every where
mention; it however seems to agree better with experiment than any other, and therefore I
have often adapted my explanations to it. [49]
The anonymous translator (actually Thomas Beddoes, 1760–1808) was less
impressed and added the following note: “To offer any arguments against
Mr. Scheele’s doctrine of composition of heat, would be now superfluous, since
Mr. Kirwan (Notes to the treatise on Air and fire) and Fontana (Opusc. Litt. à
S. Adolph. Murray) have abundantly confuted it” [50]. When Kirwan made a last
attempt to defend the phlogiston theory with his book An Essay on Phlogiston, he
6
In the English edition of Scheele’s book, this discussion is abbreviated.
292
21 The Discovery of Oxygen
Lavoisier had carried out Scheele’s experiment, Scheele would have been the
discoverer of oxygen. This implies that Scheele could predict that heating silver
calx would give rise to a previously unknown gas. Instead, Boklund concludes that
Grimaux attempted to establish Lavoisier as an independent discoverer of oxygen.
In reality, Scheele’s letter (dated September 30) may, along with Priestley’s visit in
October, have been two factors putting Lavoisier on the right track.
According to Scheele, “the phlogiston is a true element and completely simple
principle” [47]. It could be transferred between bodies, but “phlogiston can
impossibly be obtained on its own”. It should be recalled that Scheele had talked
about hydrogen gas as “elastic phlogiston” in the late 1760s. Scheele also spoke
vaguely about the effect of phlogiston on atoms (or particles as Scheele wrote): by
the action of the heat that occupied the voids between atoms, it could cause a
material to melt or to turn into a gas.
6 Phlogiston could also put the particles in such
a situation that they absorbed all incoming light rays, or just a few. Thus, Scheele
attributed colour to the interactions between light and atoms under the influence of
phlogiston. In fact, oxidation/reduction have profound effect on light absorption and
colour, both in organic compounds, where, i.e. reduction of conjugated p-systems
blue-shifts the absorption, and in d-metal ions, which typically have very different
colours in different oxidation states.
Bergman gave a definition of phlogiston in his Instructions to Lectures in
Chemistry in 1779 (Sect. 11.2): [48] “The reason for such a nature [i.e. combustibility] lies actually in a very fine matter, which the ancients called Phlogiston.
It is so subtle that, on its own, it escapes all our senses but can still be moved from
one body to another according to the laws of affinity”. Here, Bergman does not
explicitly state that phlogiston cannot be isolated. Bergman wrote that phlogiston is
probably a constituent of all matter, but in order to render a substance combustible,
a large excess of loosely bound phlogiston is needed.
Bergman accepted Scheele’s view on oxygen and combustion, and wrote in the
second edition of his paper on elective attractions:
The third system [of explaining the nature of heat] is that of my sagacious friend
Mr. Scheele, who thinks that the matter of heat is not simple, but compounded of phlogiston and vital air [oxygen], closely combined, and that light consists of the matter of heat,
with an excess of phlogiston. His Treatise on Air and Fire will best show how he arrived at
these conclusions. This hypothesis is not without its difficulties, which I every where
mention; it however seems to agree better with experiment than any other, and therefore I
have often adapted my explanations to it. [49]
The anonymous translator (actually Thomas Beddoes, 1760–1808) was less
impressed and added the following note: “To offer any arguments against
Mr. Scheele’s doctrine of composition of heat, would be now superfluous, since
Mr. Kirwan (Notes to the treatise on Air and fire) and Fontana (Opusc. Litt. à
S. Adolph. Murray) have abundantly confuted it” [50]. When Kirwan made a last
attempt to defend the phlogiston theory with his book An Essay on Phlogiston, he
6
In the English edition of Scheele’s book, this discussion is abbreviated.
292
21 The Discovery of Oxygen