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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/03/23 23:25:43」(JST)

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Degasification is the removal of dissolved gases from liquids, especially water or aqueous solutions. There are numerous possible methods for such removal of gases from solids.

Gases are removed for various reasons. Chemists remove gases from solvents when the compounds they are working on are possibly air- or oxygen-sensitive, or when bubble formation at solid-liquid interfaces becomes a problem. The formation of gas bubbles when a liquid is frozen can also be undesirable, necessitating degassing.

Pressure reduction

The solubility of gas obeys Henry's law, that is, the amount of a dissolved gas in a liquid is proportional to its partial pressure. Therefore, placing a solution under reduced pressure makes the dissolved gas less soluble. Sonication and stirring under reduced pressure can usually enhance the efficiency. This technique is often referred to as Vacuum degasification. Specialized vacuum chambers, called vacuum degassers, are used to degas materials through pressure reduction.

Heating

Membrane degasification

Gas-liquid separation membranes allow gas but not liquid to pass through. Flowing a solution inside a gas-liquid separation membrane and vacuating outside makes the dissolved gas go out through the membrane. This method has the advantage of being able to prevent redissolution of the gas, so it is used to produce very pure solvents.

The above three methods are used to remove all dissolved gases. Below are methods for more selective removal.

Substitution by inert gas

Addition of reductant

If oxygen should be removed, the addition of reductants is sometimes effective. For example, especially in the field of electrochemistry, ammonium sulfite is frequently used as a reductant because it reacts with oxygen to form sulfate ions. Although this method can be applied only to oxygen and involves the risk of reduction of the solute, the dissolved oxygen is almost totally eliminated.

Freeze-Pump-Thaw cycling

In this laboratory-scale technique, the fluid to be degassed is placed in a Schlenk flask and flash-frozen, usually with liquid nitrogen. Next a vacuum is applied, and the flask is sealed. A warm water bath is used to thaw the fluid, and upon thawing, bubbles of gas form and escape. The process is typically repeated three times.^[1]

Degassing Wine

Yeast uses sugar to produce alcohol and carbon dioxide. In wine making, carbon dioxide is an undesired by-product for most wines. If the wine is bottled quickly after fermentation, it is important to degas the wine first before bottling.

Wineries can often skip this step by aging their wines prior to bottling. Storing the wines in steel and wood barrels for months and sometimes years allow gases to be released from the juice and escape back into the air through air-locks.

References

^ "Freeze-Pump-Thaw Degassing of Liquids". University of Washington. http://depts.washington.edu/eooptic/linkfiles/Freeze_Pump_Thaw.pdf.

English Journal

Evaluation of radon adsorption characteristics of a coconut shell-based activated charcoal system for radon and thoron removal applications.

Karunakara N1, Sudeep Kumara K2, Yashodhara I2, Sahoo BK3, Gaware JJ3, Sapra BK3, Mayya YS4.
Journal of environmental radioactivity.J Environ Radioact.2015 Feb 3;142C:87-95. doi: 10.1016/j.jenvrad.2014.12.017. [Epub ahead of print]
Radon (222Rn), thoron (220Rn), and their decay products contribute a major fraction (more than 50%) of doses received from ionisation radiation in public domain indoor environments and occupation environments such as uranium mines, thorium plants, and underground facilities, and are recognised as im
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Synthesis of an open-framework allotrope of silicon.

Kim DY1, Stefanoski S1, Kurakevych OO2, Strobel TA1.
Nature materials.Nat Mater.2015 Feb;14(2):169-73. doi: 10.1038/nmat4140. Epub 2014 Nov 17.
Silicon is ubiquitous in contemporary technology. The most stable form of silicon at ambient conditions takes on the structure of diamond (cF8, d-Si) and is an indirect bandgap semiconductor, which prevents it from being considered as a next-generation platform for semiconductor technologies. Here,
PMID 25401923

High-intensity ultrasound production of Maillard reaction flavor compounds in a cysteine-xylose model system.

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Application of high intensity ultrasound has shown potential in the production of Maillard reaction odor-active flavor compounds in model systems. The impact of initial pH, sonication duration, and ultrasound intensity on the production of Maillard reaction products (MRPs) by ultrasound processing i
PMID 25640682

Japanese Journal

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… Exhumed peridotites in metamorphic belts and mantle-derived xenoliths in volcanic rocks can provide intrinsic halogen information on the mantle, whereas halogen compositions in volcanic rocks are changed from those of their mantle source during melting and degassing processes, in which halogen behavior is not well constrained. …
NAID 130005087133

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Journal of the Vacuum Society of Japan 58(4), 134-139, 2015
The usual way to reduce outgassing from a device in vacuum is to heat up a whole vacuum chamber containing the device. However, the situation, where this method can be applied, is limited due to the …
NAID 130005068704