The sublimation It is a process through which one passes from a solid state of matter to a gaseous state, without the need to previously go through the liquid state. In that sense, it is the reverse process of inverse sublimation or deposition, a process that consists of transforming a gas into a solid in the same way. For instance: dry ice, polar evaporation, planetary accretion.
The sublimation process is a transformation of matter much less frequent than evaporation (passage from liquid to gaseous) or fusion (passage from solid to liquid), which usually requires the application of heat energy to a solid until reaching a point variable according to the nature of the matter (called sublimation point), as well as sometimes requiring the use of certain pressures.
It is often used in laboratories as a phase separation method.
Examples of sublimation
- Dry ice. Carbon dioxide (CO2) can be blended first and then frozen, to make dry ice. And this, at room temperature, recovers its original gaseous form.
- Polar evaporation. Since at the Earth’s poles (Arctic and Antarctic) the water is frozen below 0 ° C, part of it sublimates returning to the atmosphere.
- Snow in the mountains. The perpetual snow on the mountain tops is preserved in a semi-solid state, from which it can return to vapor without having to go through its liquid state, through sublimation.
- The disappearance of naphthalene. Made from benzene rings, this material is used as a preservative for clothing, repelling moths and other animals that eat it. Its typical white balls disappear on their own as they go from a solid to a gaseous state.
- Arsenic treatment. When raised above 615 ° C, arsenic, traditionally solid, loses its solid form and becomes a highly poisonous gas.
- Treatment of iodine. Subject to heating in the laboratory, the iodine crystals transform into a gas with a characteristic purple color.
- Obtaining sulfur flower. This is the name given to the presentation of sulfur in the form of a very fine powder, which is extremely useful in industrial processes. One of the ways to obtain it is through the inverse sublimation of sulfur vapor.
- Aluminum sublimation. It is a technique used to sublimate certain inks that, through this process, impregnate colors on aluminum plates and give them a specific finish.
- Purification of materials. In certain alloys or homogeneous mixtures that are normally in the form of solids (compounds with iodine, with sulfur, etc.) the mixture can be purified through sublimation, heating it under controlled conditions. It is a process similar to the distillation of liquids: one solid will sublimate and the other will remain in the container.
- The “tail” of comets. Comets are traveling rocks that, as they approach the sun, heat up and much of the CO2 that are frozen sublimates, generating its typical visible trail.
- Frost formation. At very cold ambient temperatures, water vapor undergoes a reverse sublimation or deposition process and forms ice crystals on glass and surfaces, known as “frost.”
- Planetary accretion. One of the theories about the formation of solid matter in planets and other astronomical objects is due to the inverse sublimation of gases released in supernovae, whose eventual pressure and temperature can force them to become solid matter.
- Corrosive gas sublimate. Some metallic gases such as mercuric chloride can reverse sublimate in the presence of other metals, through a very common degradation process in alchemical operations.
- Flavoring tablets. Used in bathrooms and environments to be perfumed, they work from the gradual transformation of the solid to gas, allowing to cover the entire space in which they are contained.