Sublimation ( sublimation ) - the transition of a substance from a solid state immediately to a gaseous one, bypassing a liquid one. Since the specific volume of a substance changes during sublimation and energy is absorbed ( heat of sublimation ), sublimation is a first-order phase transition .
The reverse process is desublimation . An example of desublimation is atmospheric phenomena such as frost on the surface of the earth and frost on tree branches and wires.
Content
Sublimation Examples
Sublimation of iodine
Sublimation is typical, for example, of elemental iodine I 2 , which under normal conditions does not have a liquid phase: black crystals with a blue tint immediately turn (sublimate) into gaseous molecular iodine (medical βiodineβ is an alcohol solution ).
Sublimation of ice
It lends itself well to sublimation of ice , which has determined the widespread use of this process as one of the drying methods.
Application Process
1 cold water inlet
2 Cold water outlet
3 Vacuum / gas line
4 Sublimation Camera
5 Sublimated product
6 Raw material
7 External heating
The use of sublimation in laboratory technology
One of the methods for purifying solids is based on the sublimation effect. At a certain temperature, one of the substances in the mixture sublimates at a higher rate than the other. Vapors of the substance to be purified condense on the surface to be cooled. The device used for this cleaning method is called a sublimator.
Freeze-drying
Freeze drying ( aka lyophilization; freeze drying) ( English freeze drying or lyophilization) is the process of removing solvent from frozen solutions , gels , suspensions and biological objects, based on the sublimation of hardened solvent (ice) without the formation of macro amounts of liquid phase [1] .
During industrial sublimation, the initial body is first frozen, and then it is placed in a chamber filled with vacuum or inert gases . Physically, the sublimation process continues until the concentration of water vapor in the chamber reaches a level normal for a given temperature, and therefore excess water vapor is constantly pumped out. Sublimation is used in the chemical industry , in particular, in the production of explosive or explosive substances obtained by precipitation from aqueous solutions.
Sublimation is also used in the food industry : for example, freeze-dried coffee is obtained from frozen coffee extract through vacuum dehydration. Fruits after sublimation weigh several times less, and are restored in water. Sublimated products are significantly superior to dried in nutritional value, since only water is sublimated, and many useful substances are lost during thermal evaporation.
See also
- Assimilation
- Sublimation Printer
- Sublimation Printing