The device represented by this symbol symbol is also known as an "alembic" or "distillery tube" and plays an import role the discipline of alchemy.
There is a process in alchemy called distillation, in which an evaporated substance is brought into contact with something so cold that it quickly returns to a liquid state (for more details on this process, see the various symbols for 'Distillation'). The retort is a glass container used for the part of this process that requires heating, i.e. the first phase.
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