aludel

from The Century Dictionary.

• noun In chem., a name given to one of a number of pearshaped glasses or earthen pots, used in sublimation, resembling somewhat the ancient alembic, and open at both ends so that they can be fitted together in a series.
• noun In modern times it has been applied almost exclusively to the thin earthen condensers used in the collection of mercury at the reduction-works at Almadén, Spain.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Chem.) One of the pear-shaped pots open at both ends, and so formed as to be fitted together, the neck of one into the bottom of another in succession; -- used in the process of sublimation.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun a pear-shaped pot with an opening at each end, formerly used for sublimation.