Châtelier, 1850–1936), is of general importance in science, and its origin was in
the studies of chemical equilibrium.
Arrhenius theory about electrolytic dissociation is direct consequence of one of
the crucial discoveries in science. Alessandro Giuseppe Antonio Anastasio Volta
(1745–1827), the Italian chemist and physicist, has in 1799 and 1800 performed
experiments, which resulted with the discovery of electrical current. The first source
of electrical current Volta has constructed from copper and zinc plates that in direct
contact induce electrical potential. Before this discovery—invention, the electricity
has been regarded mostly as the appearance characteristic for living beings. Such a
“vitalistic theory” has origin in investigations of Luigi Aloisio Galvani (1737–
1798), the physiologist who has observed electrical effects in frogs. Nonphysiological source of electrical current invented by Volta has also staggered the vitalistic
point of view, the concept that has finally been abandoned after the work of
Friedrich Wöhler, as it was discussed in detail in previous lectures.
Consequences of this Volta’s discovery were enormous. Electrical current
became one of the most important tools in experimental chemistry and physics. By
immersion of electrodes in solution, chemistry was oriented to method of electrolysis. The Lavoisier’s theory about water as a compound consisting from hydrogen and oxygen has been supported by electrolysis.
In chemical epistemology, electrochemical experiments have two consequences:
the rejection of vitalism, and establishing chemical dualism! Systematic experimentation with electrolysis has shown that the substances can be divided in two
classes. The substances that in electrolysis are developed at the positive electrode,
the anode, belong to the first group, and the substances that appear on the negative
electrode, the cathode, belong to the second group. For instance, metals always
collect on cathode, and the molecules which have oxygen atom of another
non-metal appear on anode. But electrolysis can be applied not only to solutions,
but also to melts of salts. As I have already discussed, thanks to the invention of the
platinum laboratory equipment, Humphry Davy has electrolysed melted salts and
isolated for the first time potassium, sodium calcium, etc.
If decomposition of substance yields two components which are electrically
opposite, then chemical affinity, the force that keeps atoms together, must be
electrical by nature. If chemical affinity is electrical by its nature, then only different
atoms could be bound. Identical atoms cannot form chemical bond; this is the basic
idea of the chemical dualism. Hydrogen cannot bind hydrogen, or, oxygen cannot
bind oxygen, but hydrogen can be bound with oxygen to form water. As it has been
mentioned, the most prominent representative of chemical dualism was Jöns Jacob
Berzelius, one of the most meritorious chemist in the development of structural
theory.
Although dualism was an advancement in science because it has linked chemical
with electrical appearances, in spite to that, it became an obstacle for the development of structural theory of complex organic molecules. Discovery of molecules
in which carbon atoms are bound to each other (Kekulé, Couper) has not been the
only overcoming of dualistic approach.
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11 Models and Reality
the studies of chemical equilibrium.
Arrhenius theory about electrolytic dissociation is direct consequence of one of
the crucial discoveries in science. Alessandro Giuseppe Antonio Anastasio Volta
(1745–1827), the Italian chemist and physicist, has in 1799 and 1800 performed
experiments, which resulted with the discovery of electrical current. The first source
of electrical current Volta has constructed from copper and zinc plates that in direct
contact induce electrical potential. Before this discovery—invention, the electricity
has been regarded mostly as the appearance characteristic for living beings. Such a
“vitalistic theory” has origin in investigations of Luigi Aloisio Galvani (1737–
1798), the physiologist who has observed electrical effects in frogs. Nonphysiological source of electrical current invented by Volta has also staggered the vitalistic
point of view, the concept that has finally been abandoned after the work of
Friedrich Wöhler, as it was discussed in detail in previous lectures.
Consequences of this Volta’s discovery were enormous. Electrical current
became one of the most important tools in experimental chemistry and physics. By
immersion of electrodes in solution, chemistry was oriented to method of electrolysis. The Lavoisier’s theory about water as a compound consisting from hydrogen and oxygen has been supported by electrolysis.
In chemical epistemology, electrochemical experiments have two consequences:
the rejection of vitalism, and establishing chemical dualism! Systematic experimentation with electrolysis has shown that the substances can be divided in two
classes. The substances that in electrolysis are developed at the positive electrode,
the anode, belong to the first group, and the substances that appear on the negative
electrode, the cathode, belong to the second group. For instance, metals always
collect on cathode, and the molecules which have oxygen atom of another
non-metal appear on anode. But electrolysis can be applied not only to solutions,
but also to melts of salts. As I have already discussed, thanks to the invention of the
platinum laboratory equipment, Humphry Davy has electrolysed melted salts and
isolated for the first time potassium, sodium calcium, etc.
If decomposition of substance yields two components which are electrically
opposite, then chemical affinity, the force that keeps atoms together, must be
electrical by nature. If chemical affinity is electrical by its nature, then only different
atoms could be bound. Identical atoms cannot form chemical bond; this is the basic
idea of the chemical dualism. Hydrogen cannot bind hydrogen, or, oxygen cannot
bind oxygen, but hydrogen can be bound with oxygen to form water. As it has been
mentioned, the most prominent representative of chemical dualism was Jöns Jacob
Berzelius, one of the most meritorious chemist in the development of structural
theory.
Although dualism was an advancement in science because it has linked chemical
with electrical appearances, in spite to that, it became an obstacle for the development of structural theory of complex organic molecules. Discovery of molecules
in which carbon atoms are bound to each other (Kekulé, Couper) has not been the
only overcoming of dualistic approach.
110
11 Models and Reality