Law of multiple proportions

For instance, the ratio of the hydrogen content in methane (CH4) and ethane (C2H6) per measure of carbon is 4:3.

The discovery of this pattern led Dalton to develop the modern theory of atoms, as it suggested that the elements combine with each other in multiples of a basic quantity.

[1] The law of multiple proportions often does not apply when comparing very large molecules.

In this particular case, Dalton was mistaken about the formulas of these compounds, and it wasn't his only mistake.

[3][4] Tin oxides are actually crystals, they don't exist in molecular form.

[9][10] The earliest definition of Dalton's observation appears in an 1807 chemistry encyclopedia: ...where two bodies combine in different proportions, if the quantity of one of them be assumed as a fixed number, the proportions of the other body that unite to it are in the simplest possible ratio to each other, being produced by multiplying the lowest proportion by a simple integral number as 2, 3, 4, &c. [...] in all cases the simple elements of bodies are disposed to unite atom to atom singly; or if either is in excess, it exceeds by a ratio to be expressed by some simple multiple of the number of its atoms.

[11]The first known writer to refer to this principle as the "doctrine of multiple proportions" was Jöns Jacob Berzelius in 1813.

[12] Dalton's atomic theory garnered widespread interest but not universal acceptance shortly after he published it because the law of multiple proportions by itself was not complete proof of the existence of atoms.