The Atomic Theory and the Development of Modern Chemistry

Abstract

MANCHESTER celebrated last week, just a little prematurely, the centenary of John Dalton's atomic theory. It was on September 6, 1803, tnat he drew up in his notebook his first table of weights of the “ultimate atoms”of hydrogen (which he took as his unit), oxygen, “azot,” carbon, sulphur, and of water, ammonia, nitrous gas, nitrous oxide, and other binary compounds of these elements. With regard to the genesis of the theory in his own mind much doubt has prevailed until recently. Dalton himself told Thomas Thomson in 1804 that he had been led to the theory from his work on marsh gas and olefiant gas. He told W. C. Henry in 1824 that his speculations were suggested by the work of Richter. And yet, oddly enough, as Sir Henry Roscoe and Dr. Harden have shown in their “New View of Dalton's Atomic Theory” the evidence is dead against the accuracy of these plausible statements. Dalton's own notebook shows that his atomic theory preceded his work on marsh gas, and his notes for a lecture delivered in 1810 give a history of his ideas which agrees with all the facts.1