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Wednesday, October 10, 2018

John Dalton and atomic theory


Photo source: Wikimedia Commons, William Stirling


John Dalton (1766-1844) was an English chemist best known for his contributions to atomic theory.


Biologist Thomas Henry Huxley said,


"Another immense service rendered by Dalton, as a corollary of the new atomic doctrine, was the creation of a system of symbolic notation, which not only made the nature of chemical compounds and processes easily intelligible and easy of recollection, but, by its very form, suggested new lines of inquiry. The atomic notation was as serviceable to chemistry as the binomial nomenclature and the classificatory schematism of Linnaeus were to zoology and botany." (The Advance of Science int he Last Half-Century, 1889)


Chemist J. R. Partington said,


"Dalton, the mathematical tutor, following up the lead of Newton, combined the whole of the results of quantitative measurement which had accumulated up to his time, in a comprehensive theory based on the concept of the chemical atom." (Higher Mathematics for Chemical Students, 1911)


The rest of this post is some quotes from Dalton.


Atoms and matter


"1. Small particles called atoms exist and compose all matter; 2. They are indivisible and indestructible; 3. Atoms of the same chemical element have the same chemical properties and do not transmute or change into different elements." (A New System of Chemical Philosophy, 1808)


"Matter, though divisible in an extreme degree, is nevertheless not infinitely divisible. That is, there must be some point beyond which we cannot go in the division of matter... I have chosen the word 'atom' to signify these ultimate particles." (Dalton's Manuscript Notes, 1810)


" taking a given volume of any gas, we seem persuaded that, let the divisions be ever so minute, the number of particles must be finite." (A New System of Chemical Philosophy, 1808)


"Berzelius' symbols are horrifying... They appear to me equally to perplex the adepts in science, to discourage the learner, as well as to cloud the beauty and simplicity of the atomic theory. " (




"Now it is one great object of this work, to shew the importance and advantage of ascertaining the relative weights of the ultimate particles, both of simple and compound bodies..." (A New System of Chemical Philosophy, 1808)


"The cause of rain is now, I consider, no longer an object of doubt. If two masses of air of unequal temperatures, by the ordinary currents of the winds, are intermixed, when saturated with a vapour, a precipitation ensues." (Quoted in On the Drainage of Lands, Towns and Buildings by Dempsey and Clark)