Sublimation (phase transition)
Sublimation is the
The reverse process of sublimation is deposition (also called desublimation), in which a substance passes directly from a gas to a solid phase, without passing through the liquid state.[4]
All solids sublime, though most sublime at extremely low rates that are hardly detectable. At
For some substances, such as carbon and arsenic, sublimation from solid state is much more achievable than evaporation from liquid state and it is difficult to obtain them as liquids. This is because the pressure of their triple point in its phase diagram (which corresponds to the lowest pressure at which the substance can exist as a liquid) is very high.
Sublimation is caused by the absorption of heat which provides enough energy for some molecules to overcome the
Confusions
While the definition of sublimation is simple, there is often confusion as to what counts as a sublimation.
False correspondence with vaporization
Vaporization (from liquid to gas) is divided into two types: vaporization on the surface of the liquid is called evaporation, and vaporization at the boiling point with formation of bubbles in the interior of the liquid is called boiling. However there is no such distinction for the solid-to-gas transition, which is always called sublimation in both corresponding cases.
Potential distinction
For clarification, a distinction between the two corresponding cases is needed. With reference to a phase diagram, the sublimation that occurs left of the solid-gas boundary, the triple point or the solid-liquid boundary (corresponding to evaporation in vaporization) may be called gradual sublimation; and the substance sublimes gradually, regardless of rate. The sublimation that occurs at the solid-gas boundary (critical sublimation point) (corresponding to boiling in vaporization) may be called rapid sublimation, and the substance sublimes rapidly. The words "gradual" and "rapid" have acquired special meanings in this context and no longer describe the rate of sublimation.[citation needed]
Misuse for chemical reaction
The term sublimation refers specifically to a physical change of state and is not used to describe the transformation of a solid to a gas in a chemical reaction. For example, the dissociation on heating of solid ammonium chloride into hydrogen chloride and ammonia is not sublimation but a chemical reaction. Similarly the combustion of candles, containing paraffin wax, to carbon dioxide and water vapor is not sublimation but a chemical reaction with oxygen.
Historical definition
Sublimation is historically used as a generic term to describe a two-step phase transition ― a solid-to-gas transition (sublimation in a more precise definition) followed by a gas-to-solid transition (deposition).[5][6] (See below)
Examples
Carbon dioxide
Solid carbon dioxide (dry ice) sublimes rapidly along the solid-gas boundary (sublimation point) below the triple point (e.g., at the temperature of −78.5 °C, at atmospheric pressure), whereas its melting into liquid CO2 can occur along the solid-liquid boundary (melting point) at pressures and temperatures above the triple point (i.e., 5.1 atm, −56.6 °C).
Water
]Naphthalene
Naphthalene, an organic compound commonly found in pesticides such as mothballs, sublimes easily because it is made of non-polar molecules that are held together only by van der Waals intermolecular forces. Naphthalene is a solid that sublimes gradually at standard temperature and pressure,[8] at a high rate, with the critical sublimation point at around 80 °C or 176 °F.[9] At low temperature, its vapour pressure is high enough, 1 mmHg at 53 °C,[10] to make the solid form of naphthalene evaporate into gas. On cool surfaces, the naphthalene vapours will solidify to form needle-like crystals.
Iodine
Other substances
Arsenic can sublime readily at high temperatures.
Cadmium and zinc sublime much more than other common materials, so they are not suitable materials for use in vacuum.[citation needed]
Purification by sublimation
Sublimation is a technique used by
Historical usage
In ancient
And Sublimations we make for three causes,
The first cause is to make the body spiritual.
The second is that the spirit may be corporeal,
And become fixed with it and consubstantial.
The third cause is that from its filthy original.
It may be cleansed, and its saltiness sulphurious
May be diminished in it, which is infectious.
Sublimation predictions
The enthalpy of sublimation has commonly been predicted using the equipartition theorem. If the lattice energy is assumed to be approximately half the packing energy,[clarification needed] then the following thermodynamic corrections can be applied to predict the enthalpy of sublimation. Assuming a 1 molar ideal gas gives a correction for the thermodynamic environment (pressure and volume) in which pV = RT, hence a correction of 1RT. Additional corrections for the vibrations, rotations and translation then need to be applied. From the equipartition theorem gaseous rotation and translation contribute 1.5RT each to the final state, therefore a +3RT correction. Crystalline vibrations and rotations contribute 3RT each to the initial state, hence −6RT. Summing the RT corrections; −6RT + 3RT + RT = −2RT.[17] This leads to the following approximate sublimation enthalpy. A similar approximation can be found for the entropy term if rigid bodies are assumed.[18][19]
Dye-sublimation printing
Dye-sub printing is a digital printing technology using full color artwork that works with polyester and polymer-coated substrates. Also referred to as digital sublimation, the process is commonly used for decorating apparel, signs and banners, as well as novelty items such as cell phone covers, plaques, coffee mugs, and other items with sublimation-friendly surfaces. The process uses the science of sublimation, in which heat and pressure are applied to a solid, turning it into a gas through an endothermic reaction without passing through the liquid phase.[citation needed]
In sublimation printing, unique sublimation dyes are transferred to sheets of “transfer” paper via liquid gel ink through a piezoelectric print head. The ink is deposited on these high-release inkjet papers, which are used for the next step of the sublimation printing process. After the digital design is printed onto sublimation transfer sheets, it is placed on a heat press along with the substrate to be sublimated.[citation needed]
In order to transfer the image from the paper to the substrate, it requires a heat press process that is a combination of time, temperature and pressure. The heat press applies this special combination, which can change depending on the substrate, to “transfer” the sublimation dyes at the molecular level into the substrate. The most common dyes used for sublimation activate at 350 degrees Fahrenheit. However, a range of 380 to 420 degrees Fahrenheit is normally recommended for optimal color.[citation needed]
The result of the sublimation process is a nearly permanent, high resolution, full color print. Because the dyes are infused into the substrate at the molecular level, rather than applied at a topical level (such as with screen printing and direct to garment printing), the prints will not crack, fade or peel from the substrate under normal conditions.[citation needed]
See also
- Ablation
- Enthalpy of sublimation
- Freeze-drying
- Freezer burn – common process involving sublimation
- Phase diagram
- Phase transitions
Table of phase transitions of matter
To From
|
Solid | Liquid | Gas | Plasma |
---|---|---|---|---|
Solid | Melting | Sublimation | ||
Liquid | Freezing | Vaporization | ||
Gas | Deposition | Condensation | Ionization | |
Plasma | Recombination |
References
- ISBN 0-03-072373-6.
- ^ a b "Sublimate". Merriam-Webster.com Dictionary.
- ^ "Sublimate". CollinsDictionary.com Dictionary.
- PMID 26796663.
- ^ "Sublime". Dictionary.com Unabridged (Online). n.d.
- ^ "Sublime". CollinsDictionary.com Dictionary.
- S2CID 129927018.
- ^
Caroll, J. (2014). Natural Gas Hydrates. Gulf Professional. p. 16. ISBN 9780128005750.
- ^ Staff writer(s) (2015). "what solids go through sublimation?". National Science Foundation and UCSB School-University partnership. Retrieved 13 November 2015.
- ^
Pavia, D. (2005). Introduction to organic laboratory technique. Thomson Brooks/Cole. pp. 781–782. ISBN 978-0534408336.
- ISBN 978-0-7637-7731-9.
- ISBN 0-444-42607-8.
- ISBN 978-0-632-02017-1.
- ^ Barrett, Francis (1815). The lives of alchemystical philosophers: with a critical catalogue of books in occult chemistry, and a selection of the most celebrated treatises on the theory and practice of the hermetic art. Macdonald and Son for Lackington, Allen, & Co. p. 233.
- ISBN 978-0873953887.
- ^ Ripley, George (1591). Compound of Alchemy.
- ^ Gavezzotti, A. (1997). Theoretical Aspects and Computer Modeling of the Molecular Solid State. Chichester: Wiley and Sons.
- PMID 24564264.
- PMID 27749062.
External links
- Media related to Sublimation at Wikimedia Commons