An aludel is a subliming

Sublimation (physics)

Sublimation is the process of transition of a substance from the solid phase to the gas phase without passing through an intermediate liquid phase...

 pot used in alchemy

Alchemy

Alchemy is an influential philosophical tradition whose early practitioners’ claims to profound powers were known from antiquity. The defining objectives of alchemy are varied; these include the creation of the fabled philosopher's stone possessing powers including the capability of turning base...

 and medieval chemistry. The term refers to a range of earthen tubes, or pots without bottoms, fitted one over another, and diminishing as they advance towards the top. The lowest is adapted to a pot, placed in a furnace, wherein the matter to be sublimed is placed. At the top is a head to retain the flowers

Precipitation (chemistry)

Precipitation is the formation of a solid in a solution or inside anothersolid during a chemical reaction or by diffusion in a solid. When the reaction occurs in a liquid, the solid formed is called the precipitate, or when compacted by a centrifuge, a pellet. The liquid remaining above the solid...

, or condensation, which ascends. An aludel was used as a condenser in the sublimation process and thus came to signify the end-stages of transformation and the symbol of creation. Also called the Hermetic Vase, the Philosopher's Egg, and the Vase of the Philosophy.