Coiled helical tube of small diameter that enhances the purity of a distilled liquid. The introduction of alembics in which the vapors condensed outside the apparatus seems to have been an improvement achieved in Europe in the twelfth or thirteenth century. One of the first results was the preparation of relatively pure alcohol, although we do not know for certain who should take the credit for the discovery. The Florentine physician Taddeo Alderotti (1223-1295) described the concentration of alcohol by means of repeated fractionated distillations in a perfectly leaktight alembic. The dome (hat) of the still was connected to a delivery tube slightly less than a meter long, which was joined to a coiled helical tube immersed in a vessel cooled by a continuous stream of cold water.