describes not only the actual phenomena but also predicts the nature of the future
processes that will be experimentally studied [4]. In addition, phlogiston theory had
also unifying power, because it classifies combustion, breathing and
oxido-reduction processes in the same category.
However, phlogiston theory has one important deficiency: it has been only
qualitative, there was no mathematical apparatus accessible for it. This weakness
has been crucial for its viability. In spite to that, phlogiston theory has initiated the
formation of another chemical theory, which, starting with more rigorous definition
of chemical elements, became the foundation of modern chemistry.
The descent of phlogiston theory (tentatively speaking) is an example of the
Popperian approach by which a good theory must be falsifiable, rather than verifiable. From Popperian view a good theory should contain the inherent possibility
of testing. There are two of such tests in the phlogiston theory, the first is the
quantitative verification on the combustion reactions, and the second is qualitative.
The first test that rejects this theory is quite evident, the mass of the combusted
metal (i.e. the mass of calx) must be smaller than the mass of the reactant-metal
because the metal has lost phlogiston by combustion. However, this contradicts
observations since the mass of calx (the metal oxide) is always greater than the
mass of metal before combustion. The theories, which did not passed tests were not
completely rejected. Instead, they were simply extended by adding so called ad hoc
theories, the concepts that cannot be independently proven. Such ad hoc theory
invented to “save” the phlogiston theory affords that phlogiston possesses a negative mass!
Qualitative test that refutes phlogiston theory is based on the observation that it is
possible to transform calx to metal without adding phlogiston (for instance by heating
with coal). Pierre Bayen (1725–1798) has carried out such experiment in 1774: by
heating the red mercury oxide (in that time called, red stone, of mercury calx) without
the presence of coal as a donor of phlogiston he prepared the starting metal—mercury.
Bayen has also observed the evolution of a gas, besides the appearance of mercury,
and that this gas can, in the reaction with mercury, yields calx again. However, Bayen
did not perceive that he has really discovered a new chemical element, oxygen, and
that this experiment is on a threshold of scientific revolution. This paradigmatic move
belonged to Antoine Laurent Lavoisier (1743–1794).
This phenomenon of combustion as a “model system” in science, which has
initiated the change of paradigm in chemistry, was in the experiment with red stone
extended with a new “submodels system”, the investigation of the nature of air.
Besides combustion, there are also other observed chemical transformations in
which air is immediately included. Even phlogistonists were noted that air is not the
same before and after combustion of a substance: the air before combustion is
without phlogiston (dephlogisticated air), but after combustion the air is changed
because it is full of phlogiston (phlogisticated air):
METAL þ DEPHLOGISTICATED AIR ! CALX þ PHLOGISTICATED AIR
6 Conceptualization of Science and Experimental Model Systems
57
processes that will be experimentally studied [4]. In addition, phlogiston theory had
also unifying power, because it classifies combustion, breathing and
oxido-reduction processes in the same category.
However, phlogiston theory has one important deficiency: it has been only
qualitative, there was no mathematical apparatus accessible for it. This weakness
has been crucial for its viability. In spite to that, phlogiston theory has initiated the
formation of another chemical theory, which, starting with more rigorous definition
of chemical elements, became the foundation of modern chemistry.
The descent of phlogiston theory (tentatively speaking) is an example of the
Popperian approach by which a good theory must be falsifiable, rather than verifiable. From Popperian view a good theory should contain the inherent possibility
of testing. There are two of such tests in the phlogiston theory, the first is the
quantitative verification on the combustion reactions, and the second is qualitative.
The first test that rejects this theory is quite evident, the mass of the combusted
metal (i.e. the mass of calx) must be smaller than the mass of the reactant-metal
because the metal has lost phlogiston by combustion. However, this contradicts
observations since the mass of calx (the metal oxide) is always greater than the
mass of metal before combustion. The theories, which did not passed tests were not
completely rejected. Instead, they were simply extended by adding so called ad hoc
theories, the concepts that cannot be independently proven. Such ad hoc theory
invented to “save” the phlogiston theory affords that phlogiston possesses a negative mass!
Qualitative test that refutes phlogiston theory is based on the observation that it is
possible to transform calx to metal without adding phlogiston (for instance by heating
with coal). Pierre Bayen (1725–1798) has carried out such experiment in 1774: by
heating the red mercury oxide (in that time called, red stone, of mercury calx) without
the presence of coal as a donor of phlogiston he prepared the starting metal—mercury.
Bayen has also observed the evolution of a gas, besides the appearance of mercury,
and that this gas can, in the reaction with mercury, yields calx again. However, Bayen
did not perceive that he has really discovered a new chemical element, oxygen, and
that this experiment is on a threshold of scientific revolution. This paradigmatic move
belonged to Antoine Laurent Lavoisier (1743–1794).
This phenomenon of combustion as a “model system” in science, which has
initiated the change of paradigm in chemistry, was in the experiment with red stone
extended with a new “submodels system”, the investigation of the nature of air.
Besides combustion, there are also other observed chemical transformations in
which air is immediately included. Even phlogistonists were noted that air is not the
same before and after combustion of a substance: the air before combustion is
without phlogiston (dephlogisticated air), but after combustion the air is changed
because it is full of phlogiston (phlogisticated air):
METAL þ DEPHLOGISTICATED AIR ! CALX þ PHLOGISTICATED AIR
6 Conceptualization of Science and Experimental Model Systems
57