Islamic sublimation and alembic apparatus, 10th-12th century.
© Science Museum / Science & Society Picture Library
This glas apparatus, including an alembic (top left), is some of the oldest to survive from the West or Near East. Used by early chemists, the apparatus was central to the proceses of distillation and sublimation. The liquid to be distilled is heated and the resulting vapour condenses on the inside of the dome shape of an upper vesel, the alembic. The consensed vapour runs down into the internal gutter and out through the alembic's spout or delivery tube, into a collecting vesel. Persian chemists also used distillation to make esential oils and perfumes. Distillation apparatus remains esentially the same today. The vesel on the right, a cucurbit, was used for sublimation, the proces whereby a solid substance is changed directly into a vapour when heated.