hydrogen, 12 for carbon, and 16 for oxygen, were the immediate result of the
Cannizzaro’s idea about the existence of two-atomic molecules. Congress in
Karlsruhe was the germ for the later establishment of the International Union of
Pure and Applied Chemistry (I.U.P.A.C.).
Volta’s discovery of electrical current and electrolysis has been extended in new
branch of chemistry, the electrochemistry, which became a quantitative discipline
after the work of Michael Faraday (1791–1867), who found the correlation
between the mass of the substance produced by electrolysis with the amount of the
charge used for this reaction. In this way, the value amount, which is expressed in
units called mol, could be used not only for the amount of substance, but also for
the amount of charge. By Faraday, 1 mol of charge corresponds to 96500 C (C,
coulomb, is the unit for charge), the number that is known as Faraday constant.
The remained open question was the nature of the carrier of charge. The answer has
emerged at the end of 19th century when Sir Joseph John Thomson (1856–1940)
has discovered electron. Thomson considers electron as a part of atom, which is
responsible for chemical affinity—the binding of atoms in molecules. Electrons of
atoms that bind each other form pairs called chemical bond, the basic phenomenon
that determines molecular structure [6, 7]. This was the beginning of the concept of
chemical bond as an electron pair, the concept that will finally reshape the classical
structural theory.
In 1910, Robert A. Millikan (1868 –1953) has succeeded to determine
experimentally the charge of electron that is equal to 1,602 x 10
−19 C. This measurement has enabled the accurate calculation of Avogadro constant (N A ) by
dividing Faraday constant with the charge of electron: (96400 C)/(1,59 x 10
−19 C) =
6,025 x 10
23 = N A . Numerical determination of Avogadro’s constant was the crucial
scientific achievement because it has opened the door for the immediate study of
microcosmos by using exact experimental methods. Measured parameters obtained
by the observation of systems with particular amount of substance could be, by
using Avogadro constant, easily recalculated in the properties of single molecule.
Dalton’s transductive approach in connecting abstract concept with the measured
ratios of masses now seems visionary. Thus, it must be pointed out that Dalton did
not only discovered atoms, but he also made s step forward in the development of
epistemology of natural sciences.
The method of transduction has been proliferated in science after the construction of new scientific instruments. Robert Wilhelm Eberhard Bunsen (1811–
1899) and Gustav Robert Kirchhoff (1824–1887) have revealed their first studies
about spectral analysis, the method that is today known as spectroscopy, the branch
of science that connects observable characteristics of spectra with chemical composition and structure. In the beginning, the spectra analysed within the visible
region were used for the characterization of metals. Very interesting was the fact
that the same spectrum has been obtained either by observation of stars, or by
observation of hot metal vapours in the flame. The spectrum is, thus, directly
connected to the identity of metal—the chemical element. However, for the linkage
of abstract theory of molecular structure with observations, the additional methods
were necessary. Discovery of X-rays by Wilhelm Conrad Röntgen (1845–1923)
11 Models and Reality
113
Cannizzaro’s idea about the existence of two-atomic molecules. Congress in
Karlsruhe was the germ for the later establishment of the International Union of
Pure and Applied Chemistry (I.U.P.A.C.).
Volta’s discovery of electrical current and electrolysis has been extended in new
branch of chemistry, the electrochemistry, which became a quantitative discipline
after the work of Michael Faraday (1791–1867), who found the correlation
between the mass of the substance produced by electrolysis with the amount of the
charge used for this reaction. In this way, the value amount, which is expressed in
units called mol, could be used not only for the amount of substance, but also for
the amount of charge. By Faraday, 1 mol of charge corresponds to 96500 C (C,
coulomb, is the unit for charge), the number that is known as Faraday constant.
The remained open question was the nature of the carrier of charge. The answer has
emerged at the end of 19th century when Sir Joseph John Thomson (1856–1940)
has discovered electron. Thomson considers electron as a part of atom, which is
responsible for chemical affinity—the binding of atoms in molecules. Electrons of
atoms that bind each other form pairs called chemical bond, the basic phenomenon
that determines molecular structure [6, 7]. This was the beginning of the concept of
chemical bond as an electron pair, the concept that will finally reshape the classical
structural theory.
In 1910, Robert A. Millikan (1868 –1953) has succeeded to determine
experimentally the charge of electron that is equal to 1,602 x 10
−19 C. This measurement has enabled the accurate calculation of Avogadro constant (N A ) by
dividing Faraday constant with the charge of electron: (96400 C)/(1,59 x 10
−19 C) =
6,025 x 10
23 = N A . Numerical determination of Avogadro’s constant was the crucial
scientific achievement because it has opened the door for the immediate study of
microcosmos by using exact experimental methods. Measured parameters obtained
by the observation of systems with particular amount of substance could be, by
using Avogadro constant, easily recalculated in the properties of single molecule.
Dalton’s transductive approach in connecting abstract concept with the measured
ratios of masses now seems visionary. Thus, it must be pointed out that Dalton did
not only discovered atoms, but he also made s step forward in the development of
epistemology of natural sciences.
The method of transduction has been proliferated in science after the construction of new scientific instruments. Robert Wilhelm Eberhard Bunsen (1811–
1899) and Gustav Robert Kirchhoff (1824–1887) have revealed their first studies
about spectral analysis, the method that is today known as spectroscopy, the branch
of science that connects observable characteristics of spectra with chemical composition and structure. In the beginning, the spectra analysed within the visible
region were used for the characterization of metals. Very interesting was the fact
that the same spectrum has been obtained either by observation of stars, or by
observation of hot metal vapours in the flame. The spectrum is, thus, directly
connected to the identity of metal—the chemical element. However, for the linkage
of abstract theory of molecular structure with observations, the additional methods
were necessary. Discovery of X-rays by Wilhelm Conrad Röntgen (1845–1923)
11 Models and Reality
113