>Yes of course. Most metals are not found in their pure elemental forms and need to be smelted in order to isolate them. The same applies to brass. Melting is would destroy the brass crystal structure and allow the copper and tin to be separated based on their different melting points and densities.

If you melt a sample of bronze completely, you end up with a solution (not a mixture) of tin in copper that won't stratify by density for the same reason that a solution of ethanol in water (like vodka) doesn't stratify by density.

It's possible to separate tin from copper through repeated partial melt cycles, but yield would be absolutely terrible.

>Edit: Based on this paper it seems the most common method of separating copper and tin in brass is by chemical extraction. There are some acids which dissolve tin but not copper. Soaking brass in one of these acids will eventually lead to the tin being leached out of the brass, leaving behind solid copper and a liquid zinc solution. https://www.sciencedirect.com/science/article/pii/S1319610312001706

Note that this process is performed on slag that's particulate matter with a diameter less than 100 um (effectively sand) because otherwise the surface area to volume ratio is impractical.