sublimation
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During sublimation, a substance changes from a solid to a gas without first changing to a liquid. Very few chemicals sublimate; those that do include iodine, arsenic, and zinc chloride.
Conversion of a solid to vapour without passing through the liquid phase. It is one of the changes of state of matter.
Sublimation depends on the fact that the boiling point of the solid substance is lower than its melting point at atmospheric pressure. Thus by increasing pressure, a substance that sublimes can be made to go through a liquid stage before passing into the vapour state.
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.
| During sublimation, nonvolatile impurities which are originally present are left behind, enabling those substances which sublime to be purified. Arsenious acid, benzoic acid, and sulphur are purified by this means. |
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