Deduction, probability theory

A rational deduction of elemental abundance from solar and stellar spectra had to be based on quantum theory, and the necessary foundation was laid with the Indian physicist Meghnad Saha s theory of 1920. Saha, who as part of his postdoctoral work had stayed with Nernst in Berlin, combined Bohr s quantum theory of atoms with statistical thermodynamics and chemical equilibrium theory. Making an analogy between the thermal dissociation of molecules and the ionization of atoms, he carried the van t Hoff-Nernst theory of reaction-isochores over from the laboratory to the stars. Although his work clearly belonged to astrophysics, and not chemistry, it relied heavily on theoretical methods introduced by and associated with physical chemistry. This influence from physical chemistry, and probably from his stay with Nernst, is clear from his 1920 paper where he described ionization as a sort of chemical reaction, in which we have to substitute ionization for chemical decomposition. [81] The influence was even more evident in a second paper of 1922 where he extended his analysis. [82]... 

Nevertheless, as we know, the predictions of Newtonian mechanics for the earthly confines of structural engineers, are highly dependable and very useful. It seems therefore that we are forced to the conclusion that the probability that Newton s Laws are true, is very small, but that the deductions we can make based upon them are highly dependable. Structural analysis is built on theory which is probably not true, but one which is dependable. 

In a continuation Berzelius explains his symbols and formulae (see p. 158), and how the weight of the elementary volume relative to the unit volume of oxygen = 100 in weight is to be found. An example of the application of the volume theory is the deduction of the atomic weight of carbon. When oxygen combines with carbon to form carbonic oxide its volume is doubled, and since gaseous bodies on combination either preserve their volume or contract, the dilatation cannot be attributed to the oxygen but to the addition of one volume of carbon vapour, so that the formula of the oxide is probably... 

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