Freeze distillation is a term for a process of enriching a solution by
partially freezing it and removing frozen material that is poorer in the dissolved material than is the liquid portion left behind. Such enrichment parallels enrichment by true
distillation, where the evaporated and recondensed portion is richer than the liquid portion left behind.
Such enrichment by freezing of a solution in water is sometimes oversimplified by saying that, for instance, because of the difference in
freezing points of water (0 °C/32 °F), and ethyl alcohol (-114 °C/-173 °F), “the water freezes into ice...while the
ethyl alcohol remains liquid.” This is false, and although some of the implications of that description are true and useful, other conclusions drawn from it would be false.
The detailed situation is the subject of
thermodynamics, a subdivision of
physics of importance to
chemistry. Without resorting to mathematics, the following can be said:
- Freezing in this scenario would begin at a temperature significantly below 0 °C.
- The first material to freeze would not be water, but a dilute solution of alcohol in water.
- The liquid left behind would be richer in alcohol, and as a consequence, further freezing would take place at progressively lower temperatures, and the frozen material, while always poorer in alcohol than the (increasingly rich) liquid, would become progressively richer in alcohol.
- Further stages of removing frozen material and waiting for more freezing will come to nought once the liquid uniformly cools to the temperature of whatever is cooling it.
- If progressively colder temperatures are available,
- the frozen material will contain progressively larger concentrations of alcohol, and
- the fraction of the original alcohol removed with the solid material will increase.
- In practice, unless the removal of solid material carries away liquid, the degree of concentration will depend on the final temperature rather than on the number of cycles of removing solid material and chilling.
- Thermodynamics gives fair assurance, even without more information about alcohol and water than that they freely dissolve in each other, that
- even if temperatures somewhat below the freezing point of ethyl alcohol are achieved, there will still be alcohol and water mixed as a liquid, and
- at some still lower temperature, the remaining alcohol-and-water solution will freeze without an alcohol-poor solid being separable.
In practice, while not able to produce an alcohol concentration comparable to
distillation, this technique can achieve some concentration with far less effort than any practical distillation apparatus would require.
Today, freeze distillation of alcoholic beverages is illegal in many countries because a number of by-products of fermentation (
fusel alcohols), which are mostly removed by heat distillation, tend to accumulate to an unhealthy level in freeze-distilled beverages.
The best-known freeze-distilled
beverages are
applejack and ice beer.
Ice wine is the result of a similar process, but in this case, the freezing happens
before the fermentation, and thus it is sugar, not alcohol, that gets concentrated.
See also
Fractional freezing is a process used in process engineering and chemistry to separate two liquids with different melting points. It can be done by partial melting of a solid, for example in zone refining of silicon or metals, or by partial crystallization of a liquid, for example
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Distillation is a method of separating chemical substances based on differences in their volatilities in a boiling liquid mixture. Distillation usually forms part of a larger chemical process, and is thus referred to as a unit operation.
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Freezing point can refer to several things:
- For the chemistry term, see Melting point.
- For the news journal in the People's Republic of China, see Freezing Point.
- For the 1966 Japanese film, see Freezing Point (1966 film).
..... Click the link for more information. Ethanol, also known as ethyl alcohol, drinking alcohol or grain alcohol, is a flammable, colorless, slightly toxic chemical compound, and is best known as the alcohol found in alcoholic beverages.
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Thermodynamics (from the Greek θερμη, therme, meaning "heat" and δυναμις, dynamis, meaning "power") is a branch of physics that studies the effects of changes in temperature, pressure, and volume on
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Physics is the science of matter[1] and its motion[2][3], as well as space and time[4][5] —the science that deals with concepts such as force, energy, mass, and charge.
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Distillation is a method of separating chemical substances based on differences in their volatilities in a boiling liquid mixture. Distillation usually forms part of a larger chemical process, and is thus referred to as a unit operation.
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Fusel alcohols, also sometimes called fusel oils, or potato oil in Europe, are higher order (more than two carbons) alcohols formed by fermentation and present in cider, mead, beer, wine, and spirits to varying degrees.
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distilled beverage is a consumable liquid containing ethyl alcohol (ethanol) purified by distillation from a fermented substance such as fruit, vegetables, or grain. The word spirits
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Applejack is a strong alcoholic beverage produced from apples, originating from the American colonial period. It is made by concentrating hard cider, either by the traditional method of freeze distillation (see fractional freezing), or by true evaporative distillation.
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Icewine (or ice wine or, in German, Eiswein) is a type of dessert wine produced from grapes that have been frozen while still on the vine. The sugars and other dissolved solids do not freeze, but the water does, so the result is a concentrated, often very sweet wine.
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Fractional freezing is a process used in process engineering and chemistry to separate two liquids with different melting points. It can be done by partial melting of a solid, for example in zone refining of silicon or metals, or by partial crystallization of a liquid, for example
..... Click the link for more information.
Zone melting is a method of separation by melting in which a molten zone traverses a long ingot of impure metal or chemical. In its common use for purification, the molten region melts impure solid at its forward edge and leaves a wake of purer material solidified behind it as it
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