The development of the atomic theory.

  • Andrew Norman Meldrum
Date:
[1910-1911]
Catalogue details

Licence: In copyright

Credit: The development of the atomic theory. Source: Wellcome Collection.

    71/114
    VI. The Development of the Atomic Theory: (5) Dalton’s Chemical Theory. By Andrew Norman Meldrum, D.Sc. ( Carnegie Research Fellow.) (Communicated by Prof. H. B. Dixon, M.A., P.P.S.) Received October, igio. Read January 24th, iqu. Introduction. In the year 1801 Dalton’s physical atomic theory (described in the fourth paper of this series) was devised as an explanation of the diffusion of gases. Since the pre- vailing tendency of the time had been to regard diffusion as due to chemical affinity between the gases concerned, Dalton was forced to consider carefully the nature of physical and chemical changes, and to draw a distinction between them. His own theory of diffusion turned on this distinction. Thus, in the course of his argument against the supposition that diffusion is due to chemical affinity, he asks the question, “ Why do not oxygenous and azotic gases, taken in clue proportion and mixed, constitute nitric acid gas, another elastic fluid, totally distinct in its properties, from either of the ingredients.”1 Obviously, therefore, whilst Dalton’s attention was being directed principally to physical phenomena, he had in his mind a distinct conception of chemical change. The object of this paper is to consider how Dalton passed from the physical atomic theory, which was formed first, to the chemical one, which was formed afterwards. The author has already shown, in the second paper of this series, that the various narratives we possess of the origin of the chemical theory, can be traced back to 1 Manchester Memoirs, vol. 5, pp. 538-539, 1802. March y/h, ign.
    digitised image 1
    digitised image 2
    digitised image 3