Here's my my point: There are those that suggest that there are temperatures at which 100% of the propane in a canister will burn off but 0% of the butane will burn. This is incorrect. No such temperatures exist.
HJ
Fractionation (in this specific case where the driving force is boiling point) is actually independent of temperature. At zero degrees Kelvin, evaporation is measured in molecules/fortnight, but the the lighter constituents will still fractionate, and at terrestrial temperatures it's faster, but still proportional to the boiling points of the constituent molecules.
Fractionation is useful in this context because it is widely defined and understood by the scientific community. In this case we are looking at the residue left in the container - it might be the reverse of what you are expecting, but it is still the exact same scientific principle.
