Abstract
II. IN making brass, if we mix zinc and copper together we find no very manifest signs of chemical affinity at all; there is not a great deal of heat developed: the mixture does not become warm, it does not explode. Hence we can infer certainly that contact-electricity action ceases, or does not go on increasing according to the same law, when the metals are subdivided to something like 1/100,000,000 of a centimetre. Now this is an exceed ingly important argument. I have more decided data as to the actual magnitude of atoms or molecules to bring before you presently, but I have nothing more decided in giving for certain a limit to supposable smallness. We cannot reduce zinc and copper beyond a certain thickness, without putting them into a condition in which they lose their properties as wholes, and in which, if put together, we should not find the same attraction as we should calculate upon from the thicker plates. I think it is im possible consistently with the knowledge we have of chemical affinities and of the effect of melting zinc and copper together, to admit that a piece of copper or zinc could be divided to a thinness of much less, if at all less, than 1/100,000,000 of a centimetre without separating the atoms or dividing the molecules, or doing away with the composition which constitutes as a whole the solid metal. In short, the structure as it were of bricks, or molecules, or atoms, of which copper and zinc are built up; cannot be much, if at all, less than 1/100,000,000 of a centimetre in diameter, and may be considerably greater.
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References
See article "On the Size of Atoms," published in NATURE, vol. i. p. 551; printed in Thomson and Tait's "Natural Philosophy," second edition, 1883, vol. i. part 2, Appendix F.
First described in a letter to Joule, published in the Proceedings of the Literary and Philosophical Society of Manchester of Jan. 21, 1862, where also I first pointed out the demonstration of a limit to the size of molecules from measurements of contact electricity. The mode of measurement is more fully described in the article of NATURE (vol. xxiii. p. 567), referred to above.
For an account of the dynamical theory of the "Dispersion of Light," see "View of the Undulatory Theory as Applied to the Dispersion of Light," by the Rev. Baden Powell, M. A., &c. (London: 1841)
Loschmidt, "quoting from the Zollvereins department of the London International Exhibition of 1862, page 83. and from Harting On the Microscope, pages 881," Sitzungsberichte der Wiener Akademie Math. Phys. 1865. Vol. lii.
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The Size of Atoms 1 . Nature 28, 250–254 (1883). https://doi.org/10.1038/028250a0
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DOI: https://doi.org/10.1038/028250a0