Still
Encyclopedia
A still is a permanent apparatus used to distill
miscible or immiscible (eg. steam distillation
) liquid
mixtures by heating to selectively boil
and then cooling to condense
the vapor
. Stills have been used to produce perfume
and medicine
, Water for Injection (WFI) for pharmaceutical use, generally to separate and purify different chemicals, and most famously, to produce distilled beverage
s containing ethyl alcohol
.
Since ethyl alcohol boil
s at a lower temperature
than water
, a common application of the process of distillation is to produce strong alcoholic drinks. Usually a still used for this purpose is made of copper
, since it removes sulfur
-based compounds from the alcohol that would make it unpleasant to drink. Modern stills are made of stainless steel with copper innards (piping, for example, will be lined with copper along with copper plate inlays along still walls). Using this combination of metals is much cheaper as it prevents erosion of the entire vessel and lowers copper levels in the waste product (which in large distilleries is processed to become animal feed). All copper stills will require repairs about every 8 years because of copper erosion from the compounds it is designed to remove; this erosion is therefore unavoidable. The alcohol industry was the first to use anything close to a modern distillation apparatus and led the way in developing what is now a large part of the chemical industry.
There is also an increasing usage of distillation of gin
under glass and PTFE, and even at reduced pressures, to facilitate a fresher product. This is irrelevant to alcohol quality, because the process starts with triple distilled grain alcohol, and the distillation is used solely to harvest botanical flavors such as limonene
and other terpene
like compounds. The ethyl alcohol is relatively unchanged.
The simplest standard distillation
apparatus is commonly known as a pot still
, consisting of a single heated chamber and a vessel to collect purified alcohol. A pot still incorporates only one condensation
, whereas other types of distillation equipment have multiple stages which result in higher purification of the more volatile component (alcohol). Pot still distillation gives an incomplete separation
, but this can be desirable for the flavor of some distilled beverages.
If a purer distillate is desired, a reflux still is the most common solution. Reflux stills incorporate a fractionating column
, commonly created by filling copper vessels with glass beads to maximize available surface area
. As alcohol boils, condenses, and reboils through the column, the effective number of distillations greatly increases. Vodka
and gin
and other neutral grain spirits are distilled by this method, then diluted to concentrations appropriate for human consumption.
Alcoholic products from home distilleries are common throughout the world, but are sometimes in violation of local statutes. The product of illegal stills in the United States
is commonly referred to as moonshine
and in Ireland
, poteen.
Distillation
Distillation is a method of separating mixtures based on differences in volatilities of components in a boiling liquid mixture. Distillation is a unit operation, or a physical separation process, and not a chemical reaction....
miscible or immiscible (eg. steam distillation
Steam distillation
Steam distillation is a special type of distillation for temperature sensitive materials like natural aromatic compounds....
) liquid
Liquid
Liquid is one of the three classical states of matter . Like a gas, a liquid is able to flow and take the shape of a container. Some liquids resist compression, while others can be compressed. Unlike a gas, a liquid does not disperse to fill every space of a container, and maintains a fairly...
mixtures by heating to selectively boil
Boiling
Boiling is the rapid vaporization of a liquid, which occurs when a liquid is heated to its boiling point, the temperature at which the vapor pressure of the liquid is equal to the pressure exerted on the liquid by the surrounding environmental pressure. While below the boiling point a liquid...
and then cooling to condense
Condensation
Condensation is the change of the physical state of matter from gaseous phase into liquid phase, and is the reverse of vaporization. When the transition happens from the gaseous phase into the solid phase directly, the change is called deposition....
the vapor
Vapor
A vapor or vapour is a substance in the gas phase at a temperature lower than its critical point....
. Stills have been used to produce perfume
Perfume
Perfume is a mixture of fragrant essential oils and/or aroma compounds, fixatives, and solvents used to give the human body, animals, objects, and living spaces "a pleasant scent"...
and medicine
Medicine
Medicine is the science and art of healing. It encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness....
, Water for Injection (WFI) for pharmaceutical use, generally to separate and purify different chemicals, and most famously, to produce distilled beverage
Distilled beverage
A distilled beverage, liquor, or spirit is an alcoholic beverage containing ethanol that is produced by distilling ethanol produced by means of fermenting grain, fruit, or vegetables...
s containing ethyl alcohol
Ethanol
Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a...
.
Application
Boiling point
The boiling point of an element or a substance is the temperature at which the vapor pressure of the liquid equals the environmental pressure surrounding the liquid....
s at a lower temperature
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
than water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
, a common application of the process of distillation is to produce strong alcoholic drinks. Usually a still used for this purpose is made of copper
Copper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...
, since it removes sulfur
Sulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...
-based compounds from the alcohol that would make it unpleasant to drink. Modern stills are made of stainless steel with copper innards (piping, for example, will be lined with copper along with copper plate inlays along still walls). Using this combination of metals is much cheaper as it prevents erosion of the entire vessel and lowers copper levels in the waste product (which in large distilleries is processed to become animal feed). All copper stills will require repairs about every 8 years because of copper erosion from the compounds it is designed to remove; this erosion is therefore unavoidable. The alcohol industry was the first to use anything close to a modern distillation apparatus and led the way in developing what is now a large part of the chemical industry.
There is also an increasing usage of distillation of gin
Gin
Gin is a spirit which derives its predominant flavour from juniper berries . Although several different styles of gin have existed since its origins, it is broadly differentiated into two basic legal categories...
under glass and PTFE, and even at reduced pressures, to facilitate a fresher product. This is irrelevant to alcohol quality, because the process starts with triple distilled grain alcohol, and the distillation is used solely to harvest botanical flavors such as limonene
Limonene
Limonene is a colourless liquid hydrocarbon classified as a cyclic terpene. The more common D isomer possesses a strong smell of oranges. It is used in chemical synthesis as a precursor to carvone and as a renewably-based solvent in cleaning products....
and other terpene
Terpene
Terpenes are a large and diverse class of organic compounds, produced by a variety of plants, particularly conifers, though also by some insects such as termites or swallowtail butterflies, which emit terpenes from their osmeterium. They are often strong smelling and thus may have had a protective...
like compounds. The ethyl alcohol is relatively unchanged.
The simplest standard distillation
Distillation
Distillation is a method of separating mixtures based on differences in volatilities of components in a boiling liquid mixture. Distillation is a unit operation, or a physical separation process, and not a chemical reaction....
apparatus is commonly known as a pot still
Pot still
A pot still is a type of still used in distilling spirits such as whisky or brandy. Heat is applied directly to the pot containing the wash or wine . This is called a batch distillation ....
, consisting of a single heated chamber and a vessel to collect purified alcohol. A pot still incorporates only one condensation
Condensation
Condensation is the change of the physical state of matter from gaseous phase into liquid phase, and is the reverse of vaporization. When the transition happens from the gaseous phase into the solid phase directly, the change is called deposition....
, whereas other types of distillation equipment have multiple stages which result in higher purification of the more volatile component (alcohol). Pot still distillation gives an incomplete separation
Separation process
In chemistry and chemical engineering, a separation process, or simply a separation, is any mass transfer process used to convert a mixture of substances into two or more distinct product mixtures, at least one of which is enriched in one or more of the mixture's constituents. In some cases, a...
, but this can be desirable for the flavor of some distilled beverages.
If a purer distillate is desired, a reflux still is the most common solution. Reflux stills incorporate a fractionating column
Fractionating column
A fractionating column or fractionation column is an essential item used in the distillation of liquid mixtures so as to separate the mixture into its component parts, or fractions, based on the differences in their volatilities...
, commonly created by filling copper vessels with glass beads to maximize available surface area
Surface area
Surface area is the measure of how much exposed area a solid object has, expressed in square units. Mathematical description of the surface area is considerably more involved than the definition of arc length of a curve. For polyhedra the surface area is the sum of the areas of its faces...
. As alcohol boils, condenses, and reboils through the column, the effective number of distillations greatly increases. Vodka
Vodka
Vodka , is a distilled beverage. It is composed primarily of water and ethanol with traces of impurities and flavorings. Vodka is made by the distillation of fermented substances such as grains, potatoes, or sometimes fruits....
and gin
Gin
Gin is a spirit which derives its predominant flavour from juniper berries . Although several different styles of gin have existed since its origins, it is broadly differentiated into two basic legal categories...
and other neutral grain spirits are distilled by this method, then diluted to concentrations appropriate for human consumption.
Alcoholic products from home distilleries are common throughout the world, but are sometimes in violation of local statutes. The product of illegal stills in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
is commonly referred to as moonshine
Moonshine
Moonshine is an illegally produced distilled beverage...
and in Ireland
Ireland
Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...
, poteen.
See also
- DistillationDistillationDistillation is a method of separating mixtures based on differences in volatilities of components in a boiling liquid mixture. Distillation is a unit operation, or a physical separation process, and not a chemical reaction....
- RetortRetortIn a chemistry laboratory, a retort is a glassware device used for distillation or dry distillation of substances. It consists of a spherical vessel with a long downward-pointing neck. The liquid to be distilled is placed in the vessel and heated...
- AlembicAlembicAn alembic is an alchemical still consisting of two vessels connected by a tube...
- Column stillColumn stillA column still, also called a continuous still, patent still or Coffey still, is a variety of still consisting of two columns invented in 1826 by Robert Stein, a Clackmannanshire distiller, and it was first used at the Cameron Bridge Grain Distillery in Fife, Scotland. The design was enhanced and...
- Pot stillPot stillA pot still is a type of still used in distilling spirits such as whisky or brandy. Heat is applied directly to the pot containing the wash or wine . This is called a batch distillation ....
- Reflux still
- Solar stillSolar stillA solar still is a low-tech way of distilling water, powered by the heat of the sun . Two basic types of solar stills are box and pit stills. In a solar still, impure water is contained outside the collector, where it is evaporated by sunlight shining through clear plastic...
- Retort