Islamic sublimation apparatus, 10th-12th century.

Islamic glass sublimation apparatus with lid, now badly spalling and silvered, unsigned, Middle East, 901-1200

Sublimation apparatus, Islamic, probably 10th to 12th centuries, 2 parts, glass. In chemistry, sublimation is the conversion of a solid to vapour without passing through the liquid phase. Sublimation depends on the fact that the boiling point of the solid substance is lower than its melting point at atmospheric pressure. By increasing the pressure a substance which sublimes can be made to go through a liquid stage before passing into the vapour phase. Some substances that do not sublime at atmospheric pressure can be made to do so at low pressures. This is the principle of freeze-drying during which ice sublimes at low pressure.