Nine Books on the Nature of Things

Metals can also be separated by melting, through this process. Make the metals melt. Once they are fluid, cast in one ounce of thoroughly sublimed and purified sulphur for every pound of metal. It will burn there, and in the same action draw the lighter metal upwards, leaving the heavier at the bottom. Let them stand together in this state to cool. Two metals will thus be found in one regulus, no longer mixed as before but opposite one another, divided by sulphur as by a wall. Just as oil keeps two bodies of water apart so that they cannot unite and mix, so sulphur separates metals. Sulphur is therefore a singular arcanum worthy of exceptional praise.