I 1815 opdagede den britiske læge og kemiker [[William Prout]] at atomvægten på grundstoffer syntes at være et multiplum af hydrogen.<ref>{{cite journal|last1=Prout|first1=William|date=november 1815|title=On the relation between the specific gravities of bodies in their gaseous state and the weights of their atoms|url=https://babel.hathitrust.org/cgi/pt?id=nyp.33433062744812;view=1up;seq=351|journal=Annals of Philosophy|volume=6|pages=321–330}}</ref><ref>{{cite journal|last1=Prout|first1=William|date=februar 1816|title=Correction of a mistake in the essay on the relation between the specific gravities of bodies in their gaseous state and the weights of their atoms|url=https://babel.hathitrust.org/cgi/pt?id=nyp.33433062744820;view=1up;seq=135|journal=Annals of Philosophy|volume=7|pages=111–113}}</ref>
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