51-398: A distiller performs distillation , often to produce alcohol. Distiller or distillers may also refer to: Distillation Distillation , also classical distillation , is the process of separating the component substances of a liquid mixture of two or more chemically discrete substances; the separation process is realized by way of the selective boiling of the mixture and
102-422: A theoretical plate ) will yield a purer solution of the more volatile component. In reality, each cycle at a given temperature does not occur at exactly the same position in the fractionating column; theoretical plate is thus a concept rather than an accurate description. More theoretical plates lead to better separations. A spinning band distillation system uses a spinning band of Teflon or metal to force
153-405: A batch distillation setup (such as in an apparatus depicted in the opening figure) until the mixture is boiling results in a vapor above the liquid that contains a mixture of A and B. The ratio between A and B in the vapor will be different from the ratio in the liquid. The ratio in the liquid will be determined by how the original mixture was prepared, while the ratio in the vapor will be enriched in
204-439: A boiling point, although this is because its composition changes: each intermediate mixture has its own, singular boiling point. The idealized model is accurate in the case of chemically similar liquids, such as benzene and toluene . In other cases, severe deviations from Raoult's law and Dalton's law are observed, most famously in the mixture of ethanol and water. These compounds, when heated together, form an azeotrope , which
255-691: A dough made of rye flour. These alembics often featured a cooling system around the beak, using cold water, for instance, which made the condensation of alcohol more efficient. These were called pot stills . Today, the retorts and pot stills have been largely supplanted by more efficient distillation methods in most industrial processes. However, the pot still is still widely used for the elaboration of some fine alcohols, such as cognac , Scotch whisky , Irish whiskey , tequila , rum , cachaça , and some vodkas . Pot stills made of various materials (wood, clay, stainless steel) are also used by bootleggers in various countries. Small pot stills are also sold for use in
306-551: A lesser degree also of mineral substances, is the main topic of the De anima in arte alkimiae , an originally Arabic work falsely attributed to Avicenna that was translated into Latin and would go on to form the most important alchemical source for Roger Bacon ( c. 1220–1292 ). The distillation of wine is attested in Arabic works attributed to al-Kindī ( c. 801–873 CE ) and to al-Fārābī ( c. 872–950 ), and in
357-408: A lower concentration in the vapor. Indeed, batch distillation and fractionation succeed by varying the composition of the mixture. In batch distillation, the batch vaporizes, which changes its composition; in fractionation, liquid higher in the fractionation column contains more lights and boils at lower temperatures. Therefore, starting from a given mixture, it appears to have a boiling range instead of
408-514: A method for concentrating alcohol involving repeated distillation through a water-cooled still, by which an alcohol purity of 90% could be obtained. The distillation of beverages began in the Southern Song (10th–13th century) and Jin (12th–13th century) dynasties, according to archaeological evidence. A still was found in an archaeological site in Qinglong, Hebei province, China, dating back to
459-463: A movable liquid barrier. Finally, the entry of undesired air components can be prevented by pumping a low but steady flow of suitable inert gas, like nitrogen , into the apparatus. In simple distillation, the vapor is immediately channeled into a condenser. Consequently, the distillate is not pure but rather its composition is identical to the composition of the vapors at the given temperature and pressure. That concentration follows Raoult's law . As
510-409: A part of some process unrelated to what now is known as distillation. In the words of Fairley and German chemical engineer Norbert Kockmann respectively: The Latin "distillo," from de-stillo, from stilla, a drop, referred to the dropping of a liquid by human or artificial means, and was applied to any process where a liquid was separated in drops. To distil in the modern sense could only be expressed in
561-419: A partial distillation results in partial separations of the mixture's components, which process yields nearly-pure components; partial distillation also realizes partial separations of the mixture to increase the concentrations of selected components. In either method, the separation process of distillation exploits the differences in the relative volatility of the component substances of the heated mixture. In
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#1732859354483612-442: A result, simple distillation is effective only when the liquid boiling points differ greatly (rule of thumb is 25 °C) or when separating liquids from non-volatile solids or oils. For these cases, the vapor pressures of the components are usually different enough that the distillate may be sufficiently pure for its intended purpose. A cutaway schematic of a simple distillation operation is shown at right. The starting liquid 15 in
663-478: A roundabout manner. Distillation had a broader meaning in ancient and medieval times because nearly all purification and separation operations were subsumed under the term distillation , such as filtration, crystallization, extraction, sublimation, or mechanical pressing of oil. According to Dutch chemical historian Robert J. Forbes , the word distillare (to drip off) when used by the Romans, e.g. Seneca and Pliny
714-424: A vacuum pump. The components are connected by ground glass joints . For many cases, the boiling points of the components in the mixture will be sufficiently close that Raoult's law must be taken into consideration. Therefore, fractional distillation must be used to separate the components by repeated vaporization-condensation cycles within a packed fractionating column. This separation, by successive distillations,
765-726: A wide column with a large holdup. Conversely, a column with a low reflux ratio must have a large number of stages, thus requiring a taller column. Both batch and continuous distillations can be improved by making use of a fractionating column on top of the distillation flask. The column improves separation by providing a larger surface area for the vapor and condensate to come into contact. This helps it remain at equilibrium for as long as possible. The column can even consist of small subsystems ('trays' or 'dishes') which all contain an enriched, boiling liquid mixture, all with their own vapor–liquid equilibrium. There are differences between laboratory-scale and industrial-scale fractionating columns, but
816-416: Is a flow from the condenser back to the column, which generates a recycle that allows a better separation with a given number of trays. Equilibrium stages are ideal steps where compositions achieve vapor–liquid equilibrium, repeating the separation process and allowing better separation given a reflux ratio. A column with a high reflux ratio may have fewer stages, but it refluxes a large amount of liquid, giving
867-454: Is also referred to as rectification. As the solution to be purified is heated, its vapors rise to the fractionating column . As it rises, it cools, condensing on the condenser walls and the surfaces of the packing material. Here, the condensate continues to be heated by the rising hot vapors; it vaporizes once more. However, the composition of the fresh vapors is determined once again by Raoult's law. Each vaporization-condensation cycle (called
918-486: Is heated, the vapor pressure of each component will rise, thus causing the total vapor pressure to rise. When the total vapor pressure reaches the pressure surrounding the liquid, boiling occurs and liquid turns to gas throughout the bulk of the liquid. A mixture with a given composition has one boiling point at a given pressure when the components are mutually soluble. A mixture of constant composition does not have multiple boiling points. An implication of one boiling point
969-414: Is that lighter components never cleanly "boil first". At boiling point, all volatile components boil, but for a component, its percentage in the vapor is the same as its percentage of the total vapor pressure. Lighter components have a higher partial pressure and, thus, are concentrated in the vapor, but heavier volatile components also have a (smaller) partial pressure and necessarily vaporize also, albeit at
1020-399: Is when the vapor phase and liquid phase contain the same composition. Although there are computational methods that can be used to estimate the behavior of a mixture of arbitrary components, the only way to obtain accurate vapor–liquid equilibrium data is by measurement. It is not possible to completely purify a mixture of components by distillation, as this would require each component in
1071-427: The condensation of the vapors in a still . Dry distillation ( thermolysis and pyrolysis ) is the heating of solid materials to produce gases that condense either into fluid products or into solid products. The term dry distillation includes the separation processes of destructive distillation and of chemical cracking , breaking down large hydrocarbon molecules into smaller hydrocarbon molecules. Moreover,
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#17328593544831122-407: The vapor pressure of the liquid equals the pressure around the liquid, enabling bubbles to form without being crushed. A special case is the normal boiling point , where the vapor pressure of the liquid equals the ambient atmospheric pressure . It is a misconception that in a liquid mixture at a given pressure, each component boils at the boiling point corresponding to the given pressure, allowing
1173-505: The 12th century. Distilled beverages were common during the Yuan dynasty (13th–14th century). In 1500, German alchemist Hieronymus Brunschwig published Liber de arte distillandi de simplicibus ( The Book of the Art of Distillation out of Simple Ingredients ), the first book solely dedicated to the subject of distillation, followed in 1512 by a much expanded version. Right after that, in 1518,
1224-595: The 1st century CE. Distilled water has been in use since at least c. 200 CE , when Alexander of Aphrodisias described the process. Work on distilling other liquids continued in early Byzantine Egypt under Zosimus of Panopolis in the 3rd century. Distillation was practiced in the ancient Indian subcontinent , which is evident from baked clay retorts and receivers found at Taxila , Shaikhan Dheri , and Charsadda in Pakistan and Rang Mahal in India dating to
1275-494: The 28th book of al-Zahrāwī 's (Latin: Abulcasis, 936–1013) Kitāb al-Taṣrīf (later translated into Latin as Liber servatoris ). In the twelfth century, recipes for the production of aqua ardens ("burning water", i.e., ethanol) by distilling wine with salt started to appear in a number of Latin works, and by the end of the thirteenth century it had become a widely known substance among Western European chemists. The works of Taddeo Alderotti (1223–1296) describe
1326-734: The Elder , was "never used in our sense". Aristotle knew that water condensing from evaporating seawater is fresh: I have proved by experiment that salt water evaporated forms fresh, and the vapour does not, when it condenses, condense into sea water again. Letting seawater evaporate and condense into freshwater can not be called "distillation" for distillation involves boiling, but the experiment may have been an important step towards distillation. Early evidence of distillation has been found related to alchemists working in Alexandria in Roman Egypt in
1377-423: The boiling flask 2 is heated by a combined hotplate and magnetic stirrer 13 via a silicone oil bath (orange, 14). The vapor flows through a short Vigreux column 3, then through a Liebig condenser 5, is cooled by water (blue) that circulates through ports 6 and 7. The condensed liquid drips into the receiving flask 8, sitting in a cooling bath (blue, 16). The adapter 10 has a connection 9 that may be fitted to
1428-430: The boiling point of the mixture to rise, which results in a rise in the temperature in the vapor, which results in a changing ratio of A : B in the gas phase (as distillation continues, there is an increasing proportion of B in the gas phase). This results in a slowly changing ratio of A : B in the distillate. If the difference in vapour pressure between the two components A and B is large – generally expressed as
1479-410: The composition of the source material, the vapors of the distilling compounds, and the distillate change during the distillation. In batch distillation, a still is charged (supplied) with a batch of feed mixture, which is then separated into its component fractions, which are collected sequentially from most volatile to less volatile, with the bottoms – remaining least or non-volatile fraction – removed at
1530-902: The development of accurate design methods, such as the McCabe–Thiele method by Ernest Thiele and the Fenske equation . The first industrial plant in the United States to use distillation as a means of ocean desalination opened in Freeport, Texas in 1961 with the hope of bringing water security to the region. The availability of powerful computers has allowed direct computer simulations of distillation columns. The application of distillation can roughly be divided into four groups: laboratory scale , industrial distillation , distillation of herbs for perfumery and medicinals ( herbal distillate ), and food processing . The latter two are distinctively different from
1581-434: The difference in boiling points – the mixture in the beginning of the distillation is highly enriched in component A, and when component A has distilled off, the boiling liquid is enriched in component B. Continuous distillation is an ongoing distillation in which a liquid mixture is continuously (without interruption) fed into the process and separated fractions are removed continuously as output streams occur over time during
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1632-470: The distillation of various substances. The fractional distillation of organic substances plays an important role in the works attributed to Jābir, such as in the Kitāb al-Sabʿīn ('The Book of Seventy'), translated into Latin by Gerard of Cremona ( c. 1114–1187 ) under the title Liber de septuaginta . The Jabirian experiments with fractional distillation of animal and vegetable substances, and to
1683-403: The domestic production of flower water or essential oils . Early forms of distillation involved batch processes using one vaporization and one condensation. Purity was improved by further distillation of the condensate. Greater volumes were processed by simply repeating the distillation. Chemists reportedly carried out as many as 500 to 600 distillations in order to obtain a pure compound. In
1734-535: The early 19th century, the basics of modern techniques, including pre-heating and reflux , were developed. In 1822, Anthony Perrier developed one of the first continuous stills, and then, in 1826, Robert Stein improved that design to make his patent still . In 1830, Aeneas Coffey got a patent for improving the design even further. Coffey's continuous still may be regarded as the archetype of modern petrochemical units. The French engineer Armand Savalle developed his steam regulator around 1846. In 1877, Ernest Solvay
1785-726: The early centuries of the Common Era . Frank Raymond Allchin says these terracotta distill tubes were "made to imitate bamboo". These " Gandhara stills" were only capable of producing very weak liquor , as there was no efficient means of collecting the vapors at low heat. Distillation in China may have begun at the earliest during the Eastern Han dynasty (1st–2nd century CE). Medieval Muslim chemists such as Jābir ibn Ḥayyān (Latin: Geber, ninth century) and Abū Bakr al-Rāzī (Latin: Rhazes, c. 865–925 ) experimented extensively with
1836-418: The end. The still can then be recharged and the process repeated. In continuous distillation , the source materials, vapors, and distillate are kept at a constant composition by carefully replenishing the source material and removing fractions from both vapor and liquid in the system. This results in a more detailed control of the separation process. The boiling point of a liquid is the temperature at which
1887-448: The former two in that distillation is not used as a true purification method but more to transfer all volatiles from the source materials to the distillate in the processing of beverages and herbs. The main difference between laboratory scale distillation and industrial distillation are that laboratory scale distillation is often performed on a batch basis, whereas industrial distillation often occurs continuously. In batch distillation ,
1938-417: The industrial applications of classical distillation, the term distillation is used as a unit of operation that identifies and denotes a process of physical separation, not a chemical reaction ; thus an industrial installation that produces distilled beverages , is a distillery of alcohol . These are some applications of the chemical separation process that is distillation: Early evidence of distillation
1989-429: The liquid state , and a receiver in which the concentrated or purified liquid, called the distillate, is collected. Several laboratory scale techniques for distillation exist (see also distillation types ). A completely sealed distillation apparatus could experience extreme and rapidly varying internal pressure, which could cause it to burst open at the joints. Therefore, some path is usually left open (for instance, at
2040-411: The mixture to have a zero partial pressure . If ultra-pure products are the goal, then further chemical separation must be applied. When a binary mixture is vaporized and the other component, e.g., a salt, has zero partial pressure for practical purposes, the process is simpler. Heating an ideal mixture of two volatile substances, A and B, with A having the higher volatility, or lower boiling point, in
2091-411: The more volatile compound, A (due to Raoult's Law, see above). The vapor goes through the condenser and is removed from the system. This, in turn, means that the ratio of compounds in the remaining liquid is now different from the initial ratio (i.e., more enriched in B than in the starting liquid). The result is that the ratio in the liquid mixture is changing, becoming richer in component B. This causes
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2142-458: The oldest surviving distillery in Europe, The Green Tree Distillery , was founded. In 1651, John French published The Art of Distillation , the first major English compendium on the practice, but it has been claimed that much of it derives from Brunschwig's work. This includes diagrams with people in them showing the industrial rather than bench scale of the operation. As alchemy evolved into
2193-432: The operation. Continuous distillation produces a minimum of two output fractions, including at least one volatile distillate fraction, which has boiled and been separately captured as a vapor and then condensed to a liquid. There is always a bottoms (or residue) fraction, which is the least volatile residue that has not been separately captured as a condensed vapor. Continuous distillation differs from batch distillation in
2244-413: The principles are the same. Examples of laboratory-scale fractionating columns (in increasing efficiency) include: Laboratory scale distillations are almost exclusively run as batch distillations. The device used in distillation, sometimes referred to as a still , consists at a minimum of a reboiler or pot in which the source material is heated, a condenser in which the heated vapor is cooled back to
2295-434: The receiving flask) to allow the internal pressure to equalize with atmospheric pressure. Alternatively, a vacuum pump may be used to keep the apparatus at a lower than atmospheric pressure. If the substances involved are air- or moisture-sensitive, the connection to the atmosphere can be made through one or more drying tubes packed with materials that scavenge the undesired air components, or through bubblers that provide
2346-428: The respect that concentrations should not change over time. Continuous distillation can be run at a steady state for an arbitrary amount of time. For any source material of specific composition, the main variables that affect the purity of products in continuous distillation are the reflux ratio and the number of theoretical equilibrium stages, in practice determined by the number of trays or the height of packing. Reflux
2397-412: The science of chemistry , vessels called retorts became used for distillations. Both alembics and retorts are forms of glassware with long necks pointing to the side at a downward angle to act as air-cooled condensers to condense the distillate and let it drip downward for collection. Later, copper alembics were invented. Riveted joints were often kept tight by using various mixtures, for instance
2448-421: The solution and 2) the fraction of solution each component makes up, a.k.a. the mole fraction . This law applies to ideal solutions , or solutions that have different components but whose molecular interactions are the same as or very similar to pure solutions. Dalton's law states that the total pressure is the sum of the partial pressures of each individual component in the mixture. When a multi-component liquid
2499-400: The vapors of each component to collect separately and purely. However, this does not occur, even in an idealized system. Idealized models of distillation are essentially governed by Raoult's law and Dalton's law and assume that vapor–liquid equilibria are attained. Raoult's law states that the vapor pressure of a solution is dependent on 1) the vapor pressure of each chemical component in
2550-544: Was found on Akkadian tablets dated c. 1200 BCE describing perfumery operations. The tablets provided textual evidence that an early, primitive form of distillation was known to the Babylonians of ancient Mesopotamia . According to British chemist T. Fairley, neither the Greeks nor the Romans had any term for the modern concept of distillation. Words like "distill" would have referred to something else, in most cases
2601-400: Was granted a U.S. Patent for a tray column for ammonia distillation, and the same and subsequent years saw developments in this theme for oils and spirits. With the emergence of chemical engineering as a discipline at the end of the 19th century, scientific rather than empirical methods could be applied. The developing petroleum industry in the early 20th century provided the impetus for
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