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Essential oil
From Wikipedia, the free encyclopedia
Jump to: navigation, search
Contents
[hide]
* 1 Production
o 1.1 Distillation
o 1.2 Expression
o 1.3 Solvent extraction
o 1.4 Production quantities
* 2 Use in aromatherapy
* 3 Dilution
* 4 Raw materials
o 4.1 Rose oil
* 5 Dangers
o 5.1 Pregnancy
o 5.2 Gynecomastia
o 5.3 Pesticide residues
o 5.4 Ingestion
o 5.5 Flammability
o 5.6 Toxicology
* 6 Standardization of its derived products
* 7 Industrial resources
* 8 Notes and references
o 8.1 Additional references
* 9 See also
Not to be confused with essential fatty acid.
An essential oil is a concentrated, hydrophobic liquid containing volatile aroma
compounds from plants. Essential oils are also known as volatile, ethereal oils
or aetherolea, or simply as the "oil of" the plant from which they were
extracted, such as oil of clove. An oil is "essential" in the sense that it
carries a distinctive scent, or essence, of the plant. Essential oils do not as
a group need to have any specific chemical properties in common, beyond
conveying characteristic fragrances.
Essential oils are generally extracted by distillation. Other processes include
expression, or solvent extraction. They are used in perfumes, cosmetics, soap
and other products, for flavoring food and drink, and for scenting incense and
household cleaning products.
Various essential oils have been used medicinally at different periods in
history. Medical application proposed by those who sell medicinal oils range
from skin treatments to remedies for cancer, and are often based on historical
use of these oils for these purposes. Such claims are now subject to regulation
in most countries, and have grown more vague to stay within these regulations.
Interest in essential oils has revived in recent decades with the popularity of
aromatherapy, a branch of alternative medicine which claims that the specific
aromas carried by essential oils have curative effects. Oils are volatilized or
diluted in a carrier oil and used in massage, diffused in the air by a nebulizer
or by heating over a candle flame, or burned as incense, for example.
[edit] Production
Main article: Extraction (fragrance)
[edit] Distillation
See also: Distillation
Today, most common essential oils, such as lavender, peppermint, and eucalyptus,
are distilled. Raw plant material, consisting of the flowers, leaves, wood,
bark, roots, seeds, or peel, is put into an alembic (distillation apparatus)
over water. As the water is heated the steam passes through the plant material,
vaporizing the volatile compounds. The vapors flow through a coil where they
condense back to liquid, which is then collected in the receiving vessel.
Most oils are distilled in a single process. One exception is Ylang-ylang
(Cananga odorata), which takes 22 hours to complete through a fractional
distillation.
The recondensed water is referred to as a hydrosol, hydrolat, herbal distillate
or plant water essence, which may be sold as another fragrant product. Popular
hydrosols include rose water, lavender water, lemon balm, clary sage and orange
blossom water. The use of herbal distillates in cosmetics is increasing. Some
plant hydrosols have unpleasant smells and are therefore not sold.
[edit] Expression
Most citrus peel oils are expressed mechanically, or cold-pressed. Due to the
relatively large quantities of oil in citrus peel and low cost to grow and
harvest the raw materials, citrus-fruit oils are cheaper than most other
essential oils. Lemon or sweet orange oils that are obtained as by-products of
the citrus industry are even cheaper.
Prior to the discovery of distillation, all essential oils were extracted by
pressing.
[edit] Solvent extraction
Most flowers contain too little volatile oil to undergo expression and their
chemical components are too delicate and easily denatured by the high heat used
in steam distillation. Instead, a solvent such as hexane or supercritical carbon
dioxide is used to extract the oils. Extracts from hexane and other hydrophobic
solvent are called concretes, which is a mixture of essential oil, waxes,
resins, and other lipophilic (oil soluble) plant material.
Although highly fragrant, concretes contain large quantities of non-fragrant
waxes and resins. As such another solvent, often ethyl alcohol, which only
dissolves the fragrant low-molecular weight compounds, is used to extract the
fragrant oil from the concrete. The alcohol is removed by a second distillation,
leaving behind the absolute.
Supercritical carbon dioxide is used as a solvent in supercritical fluid
extraction. This method has many benefits, including avoiding petrochemical
residues in the product and the loss of some "top notes" when steam distillation
is used. It does not yield an absolute directly. The supercritical carbon
dioxide will extract both the waxes and the essential oils that make up the
concrete. Subsequent processing with liquid carbon dioxide, achieved in the same
extractor by merely lowering the extraction temperature, will separate the waxes
from the essential oils. This lower temperature process prevents the
decomposition and denaturing of compounds. When the extraction is complete, the
pressure is reduced to ambient and the carbon dioxide reverts back to a gas,
leaving no residue. An animated presentation describing the process is available
for viewing.
Supercritical carbon dioxide is also used for making decaffeinated coffee.
However, although it uses the same basic principles it is a different process
because of the difference in scale.
[edit] Production quantities
Estimates of total production of essential oils are difficult to obtain. One
estimate, compiled from data in 1989, 1990 and 1994 from various sources gives
the following total production, in tonnes, of essential oils for which more than
1,000 tonnes were produced.[1]
Oil Tonnes
Sweet orange 12,000
Mentha arvensis 4,800
Peppermint 3,200
Cedarwood 2,600
Lemon 2,300
Eucalyptus globulus 2,070
Litsea cubeba 2,000
Clove (leaf) 2,000
Spearmint 1,300
[edit] Use in aromatherapy
Main article: Aromatherapy
Aromatherapy is a form of alternative medicine, in which healing effects are
ascribed to the aromatic compounds in essential oils and other plant extracts.
Many common essential oils have medicinal properties that have been applied in
folk medicine since ancient times and are still widely used today. For example,
many essential oils have antiseptic properties.[2] Many are also claimed to have
an uplifting effect on the mind. The claims are supported in some studies[3][4]
and unconfirmed in others.[5]
[edit] Dilution
Essential oils are usually lipophilic (literally: "oil-loving") compounds that
usually are not miscible with water. Instead, they can be diluted in solvents
like pure ethanol (alcohol), polyethylene glycol, or oils.
[edit] Raw materials
Main article: List of essential oils
Essential oils are derived from various sections of plants. Some plants, like
the bitter orange, are sources of several types of essential oil.
Berries
* Allspice
* Juniper
Seeds
* Almond
* Anise
* Celery
* Cumin
* Nutmeg oil
Bark
* Cassia
* Cinnamon
* Sassafras
Wood
* Camphor
* Cedar
* Rosewood
* Sandalwood
* Agarwood
Rhizome
* Galangal
* Ginger
Leaves
* Basil
* Bay leaf
* Cinnamon
* Common sage
* Eucalyptus
* Lemon grass
* Melaleuca
* Oregano
* Patchouli
* Peppermint
* Pine
* Rosemary
* Spearmint
* Tea tree
* Thyme
* Wintergreen
Resin
* Frankincense
* Myrrh
Flowers
* Cannabis
* Chamomile
* Clary sage
* Clove
* Scented geranium
* Hops
* Hyssop
* Jasmine
* Lavender
* Manuka
* Marjoram
* Orange
* Rose
* Ylang-ylang
Peel
* Bergamot
* Grapefruit
* Lemon
* Lime
* Orange
* Tangerine
Root
* Valerian
[edit] Rose oil
Main article: Rose oil
The most well-known essential oil is probably rose oil, produced from the petals
of Rosa damascena and Rosa centifolia. Steam-distilled rose oil is known as
"rose otto" while the solvent extracted product is known as "rose absolute".
[edit] Dangers
Because of their concentrated nature, essential oils generally should not be
applied directly to the skin in their undiluted or "neat" form. Some can cause
severe irritation or provoke an allergic reaction. Instead, essential oils
should be blended with a vegetable-based "carrier" oil (a.k.a., a base, or
"fixed" oil) before being applied. Common carrier oils include olive, almond,
hazelnut and grapeseed. Only neutral oils should be used. A common ratio of
essential oil disbursed in a carrier oil is 0.5–3% (most under 10%), depending
on its purpose. Some essential oils, including many of the citrus peel oils, are
photosensitizers, increasing the skin's vulnerability to sunlight. Industrial
users of essential oils should consult the material safety data sheets (MSDS) to
determine the hazards and handling requirements of particular oils.
[edit] Pregnancy
The use of essential oils in pregnancy is not recommended due to inadequate
published evidence to demonstrate evidence of safety.
[edit] Gynecomastia
Estrogenic and antiandrogenic activity have been reported by in vitro study of
tea tree oil and lavender essential oils. Case reports suggest that the oils may
be implicated in some cases of gynecomastia, an abnormal breast tissue growth,
in prepubescent boys.[6][7]
[edit] Pesticide residues
There is some concern about pesticide residues in essential oils, particularly
those used therapeutically. For this reason, many practitioners of aromatherapy
buy organically produced oils.
[edit] Ingestion
While some advocate the ingestion of essential oils for therapeutic purposes,
this should never be done except under the supervision of someone licensed to
prescribe such treatment. Some common essential oils such as Eucalyptus are
toxic internally. Pharmacopoeia standards for medicinal oils should be heeded.
Some oils can be toxic to some domestic animals, cats in particular.[8] The
internal use of essential oils can pose hazards to pregnant women, as some can
be abortifacients in dose 0.5–10 ml.
[edit] Flammability
The flash point of each essential oil is different. Many of the common essential
oils such as tea tree, lavender, and citrus oils are classed as a Class 3
Flammable Liquid as they have a flash point of 50–60 °C.
[edit] Toxicology
LD50 of most essential oils or their main components are 0.5–10 mg/kg (orally or
skin test).[citation needed] This compares with, for example, the LD50 of
arsenic acid, one of the most common arsenic based poisons which is 6 mg/kg
(rabbits).[9]
[edit] Standardization of its derived products
In 2002, ISO published ISO 4720 in which the botanical names of the relevant
plants are standardized [10]. The rest of the standards with regards to this
topic can be found in the section of ICS 71.100.60 [11]
Further information: British Pharmacopoeia and United States Pharmacopoeia
[edit] Industrial resources
* Flavour and Fragrance Journal [12]
* Journal of Essential Oil Research [13]
[edit] Notes and references
1. ^ "ISO TC 54 Business Plan — Essential oils" (PDF).
http://isotc.iso.org/livelink/livelink/971087/ISO_TC_054__Essential_oils_.pdf.
Retrieved 2006-09-14. It is unclear from the source what period of time the
quoted figures include.
2. ^ Seenivasan Prabuseenivasan, Manickkam Jayakumar, and Savarimuthu
Ignacimuthu (November 30, 2006). "In vitro antibacterial activity of some plant
essential oils". BMC Complement Altern Med. 6: 39. doi:10.1186/1472-6882-6-39.
PMID 17134518.& PMC 1693916. http://www.biomedcentral.com/1472-6882/6/39.
3. ^ Komiya M, Takeuchi T, Harada E (September 25, 2006). "Lemon oil vapor
causes an anti-stress effect via modulating the 5-HT and DA activities in mice".
Behav Brain Res 172 (2): 240–9. doi:10.1016/j.bbr.2006.05.006. PMID 16780969.
http://linkinghub.elsevier.com/retrieve/pii/S0166-4328(06)00279-8. Retrieved
2006-12-24.
4. ^ Hiroko Kuriyama, Satoko Watanabe, Takaaki Nakaya, Ichiro Shigemori,
Masakazu Kita, Noriko Yoshida, Daiki Masaki, Toshiaki Tadai, Kotaro Ozasa, Kenji
Fukui, and Jiro Imanishi (September 15, 2005). "Ambient odors of orange and
lavender reduce anxiety and improve mood in a dental office". Physiol Behav 86
(1-2): 92–5. doi:10.1016/j.physbeh.2005.06.031. PMID 16095639.
5. ^ Lehrner J, Marwinski G, Lehr S, Johren P, Deecke L (June 2005).
"Immunological and Psychological Benefits of Aromatherapy Massage". Evid Based
Complement Alternat Med 2 (2): 179. doi:10.1093/ecam/neh087. PMID 15937558.
6. ^ Henley, D. V.; Lipson, N; Korach, KS; Bloch, CA (2007). "Prepubertal
gynecomastia linked to lavender and tea tree oils". New England Journal of
Medicine 356 (5): 479–85. doi:10.1056/NEJMoa064725. PMID 17267908.
7. ^ "Oils make male breasts develop". BBC News. 2007-02-01.
http://news.bbc.co.uk/2/hi/health/6318043.stm. Retrieved 2007-09-09.
8. ^ Bischoff K, Guale F (April 1998). "Australian tea tree (Melaleuca
alternifolia) oil poisoning in three purebred cats". J. Vet. Diagn. Invest. 10
(2): 208–10. PMID 9576358.
http://www.jvdi.org/cgi/pmidlookup?view=long&pmid=9576358.
9. ^ Joachimoglu. Biochem. Z. 70, 144 (1915)
10. ^ International Organization for Standardization. "ISO 4720:2002 Essential
oils — Nomenclature".
http://www.iso.org/iso/iso_catalogue/catalogue_ics/catalogue_detail_ics.htm?ics1=01&ics2=040&ics3=71&csnumber=30435.
Retrieved 23 April 2009.
11. ^ International Organization for Standardization. "71.100.60: Essential
oils".
http://www.iso.org/iso/products/standards/catalogue_ics_browse.htm?ICS1=71&ICS2=100&ICS3=60&.
Retrieved 14 June 2009.
12. ^ John Wiley & Sons. "Flavour and Fragrance Journal".
http://www3.interscience.wiley.com/journal/4029/home. Retrieved 11 July 2009.
13. ^ Allured Business Media. "Journal of Essential Oil Research".
http://www.jeoronline.com/. Retrieved 11 July 2009.
[edit] Additional references
* Kurt Schnaubelt (1999). Advanced Aromatherapy: The Science of Essential Oil
Therapy. Healing Arts Press. ISBN 0-89281-743-7.
* Wanda Sellar (2001). The Directory of Essential Oils (Reprint ed.). Essex: The
C.W. Daniel Company, Ltd. ISBN 0-85207-346-1.
* Robert Tisserand (1995). Essential Oil Safety: A Guide for Health Care
Professionals. Churchill Livingstone. ISBN 0-443-05260-3.
[edit] See also
* Alternative medicine
* Aromatherapy
* Enfleurage
* Fragrance oil
* List of essential oils
* List of vegetable oils
* Volatility (chemistry)
Retrieved from "http://en.wikipedia.org/wiki/Essential_oil"
Categories: Essential oils | Oils
Hidden categories: All articles with unsourced statements | Articles with
unsourced statements from February 2007
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[close]
Distillation
From Wikipedia, the free encyclopedia
Jump to: navigation, search
"Distiller" and "Distillery" redirect here. For other uses, see Distiller
(disambiguation) and Distillery (disambiguation).
For other uses, see Distillation (disambiguation).
Laboratory display of distillation: 1: A heating device 2: Still pot 3: Still
head 4: Thermometer/Boiling point temperature 5: Condenser 6: Cooling water in
7: Cooling water out 8: Distillate/receiving flask 9: Vacuum/gas inlet 10: Still
receiver 11: Heat control 12: Stirrer speed control 13: Stirrer/heat plate 14:
Heating (Oil/sand) bath 15: Stirring means e.g.(shown), anti-bumping granules or
mechanical stirrer 16: Cooling bath.[1]
Distillation is a method of separating mixtures based on differences in their
volatilities in a boiling liquid mixture. Distillation is a unit operation, or a
physical separation process, and not a chemical reaction.
Commercially, distillation has a number of applications. It is used to separate
crude oil into more fractions for specific uses such as transport, power
generation and heating. Water is distilled to remove impurities, such as salt
from seawater. Air is distilled to separate its components—notably oxygen,
nitrogen, and argon—for industrial use. Distillation of fermented solutions has
been used since ancient times to produce distilled beverages with a higher
alcohol content. The premises where distillation is carried out, especially
distillation of alcohol, are known as a distillery.
Contents
[hide]
* 1 History
* 2 Applications of distillation
* 3 Idealized distillation model
o 3.1 Batch distillation
o 3.2 Continuous distillation
o 3.3 General improvements
* 4 Laboratory scale distillation
o 4.1 Simple distillation
o 4.2 Fractional distillation
o 4.3 Steam distillation
o 4.4 Vacuum distillation
o 4.5 Air-sensitive vacuum distillation
o 4.6 Short path distillation
o 4.7 Other types
* 5 Azeotropic distillation
o 5.1 Breaking an azeotrope with unidirectional pressure manipulation
o 5.2 Pressure-swing distillation
* 6 Industrial distillation
* 7 Distillation in food processing
o 7.1 Distilled beverages
* 8 References
* 9 Further reading
* 10 Gallery
* 11 External links
[edit] History
Distillation apparatus of Zosimus, from Marcelin Berthelot, Collection des
anciens alchimistes grecs (3 vol., Paris, 1887-1888).
Early types of distillation were known to the Babylonians in Mesopotamia (in
what is now Iraq) from at least the 2nd millennium BC.[2] Archaeological
excavations in northwest Pakistan have yielded evidence that the distillation of
alcohol was known in the Indian subcontinent since 500 BC,[3] but only became
common between 150 BC - 350 AD.[3] Primitive tribes of India used a method of
distillation for producing Mahuda liquor. This crude and ancient method is not
very effective.[4]
Distillation was later known to Hellenistic alchemists from the 1st century
AD,[5][6][7] and the later development of large-scale distillation apparatus
occurred in response to demands for spirits.[5] According to K. B. Hoffmann the
earliest mention of "destillatio per descensum" occurs in the writings of
Aetius, a Greek physician from the 5th century.[8] Hypatia of Alexandria is
credited with having invented an early distillation apparatus,[9] and the first
clear description of early apparatus for distillation is given by Zosimos of
Panopolis in the fourth century.[7]
The invention of highly effective "pure distillation" is credited to Arabic and
Persian chemists in the Middle East from the 8th century. They produced
distillation processes to isolate and purify chemical substances for industrial
purposes such as isolating natural esters (perfumes) and producing pure
alcohol.[10] The first among them was Jabir ibn Hayyan (Geber), in the 8th
century, who is credited with the invention of numerous chemical apparatus and
processes that are still in use today. In particular, his alembic was the first
still with retorts which could fully purify chemicals, a precursor to the pot
still, and its design has served as inspiration for modern micro-scale
distillation apparatus such as the Hickman stillhead.[11] The isolation of
ethanol (alcohol) as a pure compound through distillation was first achieved by
the Arab chemist Al-Kindi (Alkindus).[12] Petroleum was first distilled by the
Persian alchemist Muhammad ibn Zakarīya Rāzi (Rhazes) in the 9th century, for
producing kerosene,[13] while steam distillation was invented by Avicenna in the
early 11th century, for producing essential oils.[14]
As the works of Middle Eastern scribes made their way to India and became a part
of Indian alchemy, several texts dedicated to distillation made their way to
Indian libraries.[15] Among these was a treatise written by a scholar from
Bagdad in 1034 titled Ainu-s-Sana'ah wa' Auna-s-Sana'ah.[15] Scholar Al-Jawbari
travelled to India.[16] By the time of the writing of the Ain-e-Akbari, the
process of distillation was well known in India.[17]
Distillation was introduced to medieval Europe through Latin translations of
Arabic chemical treatises in the 12th century.[18] In 1500, German alchemist
Hieronymus Braunschweig published Liber de arte destillandi (The Book of the Art
of Distillation)[19] the first book solely dedicated to the subject of
distillation, followed in 1512 by a much expanded version. In 1651, John French
published The Art of Distillation the first major English compendium of
practice, though it has been claimed[20] that much of it derives from
Braunschweig's work. This includes diagrams with people in them showing the
industrial rather than bench scale of the operation.
Distillation
Old Ukrainian vodka still
As alchemy evolved into 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 which acted 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 a dough made of rye flour.[21] 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, tequila 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 the domestic
production[22] of flower water or essential oils.
Early forms of distillation were 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
were reported to carry out as many as 500 to 600 distillations in order to
obtain a pure compound[23].
In the early 19th century the basics of modern techniques including pre-heating
and reflux were developed, particularly by the French[23], then in 1830 a
British Patent was issued to Aeneas Coffey for a whiskey distillation
column[24], which worked continuously and may be regarded as the archetype of
modern petrochemical units. In 1877, Ernest Solvay was granted a U.S. Patent for
a tray column for ammonia distillation[25] and the same and subsequent years saw
developments of this theme for oil 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
the development of accurate design methods such as the McCabe-Thiele method and
the Fenske equation. The availability of powerful computers has also allowed
direct computer simulation of distillation columns.
[edit] Applications of distillation
The application of distillation can roughly be divided in 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 the former two in that in the processing of
beverages, the distillation is not used as a true purification method but more
to transfer all volatiles from the source materials to the distillate.
The main difference between laboratory scale distillation and industrial
distillation is that laboratory scale distillation is often performed
batch-wise, whereas industrial distillation often occurs continuously. In batch
distillation, 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 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
better control of the separation process.
[edit] Idealized distillation model
The boiling point of a liquid is the temperature at which the vapor pressure of
the liquid equals the pressure in 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 common misconception that in a liquid mixture at a given pressure, each
component boils at the boiling point corresponding to the given pressure and the
vapors of each component will collect separately and purely. This, however, 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 assumes that a component contributes to the total vapor pressure of
the mixture in proportion to its percentage of the mixture and its vapor
pressure when pure, or succinctly: partial pressure equals mole fraction
multiplied by vapor pressure when pure. If one component changes another
component's vapor pressure, or if the volatility of a component is dependent on
its percentage in the mixture, the law will fail.
Dalton's law states that the total vapor pressure is the sum of the vapor
pressures of each individual component in the mixture. When a multi-component
liquid 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. Note that a mixture with a given composition
has one boiling point at a given pressure, when the components are mutually
soluble.
An implication of one boiling point 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 evaporate also, albeit being less
concentrated in the vapor. Indeed, batch distillation and fractionation succeed
by varying the composition of the mixture. In batch distillation, the batch
evaporates, which changes its composition; in fractionation, liquid higher in
the fractionation column contains more lights and boils at lower temperatures.
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 is a composition
with a boiling point higher or lower than the boiling point of each separate
liquid. Virtually all liquids, when mixed and heated, will display azeotropic
behaviour. 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 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 evaporated and the other component,
e.g. a salt, has zero partial pressure for practical purposes, the process is
simpler and is called evaporation in engineering.
[edit] Batch distillation
Main article: Batch distillation
A batch still showing the separation of A and B.
Heating an ideal mixture of two volatile substances A and B (with A having the
higher volatility, or lower boiling point) in 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 which 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 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 the starting liquid).
The result is that the ratio in the liquid mixture is changing, becoming richer
in component B. This causes the boiling point of the mixture to rise, which in
turn 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 A : B in the distillate.
If the difference in vapor pressure between the two components A and B is large
(generally expressed as 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.
[edit] Continuous distillation
Main article: Continuous distillation
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 as time passes during the operation.
Continuous distillation produces at least two output fractions, including at
least one volatile distillate fraction, which has boiled and been separately
captured as a vapor 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 the respect that
concentrations should not change over time. Continuous distillation can be run
at a steady state for an arbitrary amount of time. Given a feed of in a
specified composition, the main variables that affect the purity of products in
continuous distillation are the reflux ratio and the number of theoretical
equilibrium stages (practically, the number of trays or the height of packing).
Reflux 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 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.
Continuous distillation requires building and configuring dedicated equipment.
The resulting high investment cost restricts its use to the large
scale.[clarification needed]
[edit] General improvements
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 the principles are the same. Examples of
laboratory-scale fractionating columns (in increasing efficiency) include:
* Air condenser
* Vigreux column (usually laboratory scale only)
* Packed column (packed with glass beads, metal pieces, or other chemically
inert material)
* Spinning band distillation system.
[edit] Laboratory scale distillation
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 vapour is cooled back to 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).
[edit] Simple distillation
In simple distillation, all the hot vapors produced are immediately channeled
into a condenser that cools and condenses the vapors. Therefore, the distillate
will not be pure - its composition will be identical to the composition of the
vapors at the given temperature and pressure, and can be computed from Raoult's
law.
As a result, simple distillation is usually used only to separate liquids whose
boiling points differ greatly (rule of thumb is 25 °C),[26] or to separate
liquids from involatile solids or oils. For these cases, the vapor pressures of
the components are usually sufficiently different that Raoult's law may be
neglected due to the insignificant contribution of the less volatile component.
In this case, the distillate may be sufficiently pure for its intended purpose.
[edit] Fractional distillation
Main article: Fractional distillation
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 in order to separate the
components well by repeated vaporization-condensation cycles within a packed
fractionating column. This separation, by successive distillations, is also
referred to as rectification [27].
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 are determined once again by Raoult's law. Each
vaporization-condensation cycle (called a theoretical plate) will yield a purer
solution of the more volatile component.[28] 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 the rising vapors into
close contact with the descending condensate, increasing the number of
theoretical plates.[29]
[edit] Steam distillation
Main article: Steam distillation
Like vacuum distillation, steam distillation is a method for distilling
compounds which are heat-sensitive.[30] This process involves using bubbling
steam through a heated mixture of the raw material. By Raoult's law, some of the
target compound will vaporize (in accordance with its partial pressure). The
vapor mixture is cooled and condensed, usually yielding a layer of oil and a
layer of water.
Steam distillation of various aromatic herbs and flowers can result in two
products; an essential oil as well as a watery herbal distillate. The essential
oils are often used in perfumery and aromatherapy while the watery distillates
have many applications in aromatherapy, food processing and skin care.
Dimethyl sulfoxide usually boils at 189 °C. Under a vacuum, it distills off into
the receiver at only 70 °C.
Perkin triangle distillation setup
1: Stirrer bar/anti-bumping granules 2: Still pot 3: Fractionating column 4:
Thermometer/Boiling point temperature 5: Teflon tap 1 6: Cold finger 7: Cooling
water out 8: Cooling water in 9: Teflon tap 2 10: Vacuum/gas inlet 11: Teflon
tap 3 12: Still receiver
[edit] Vacuum distillation
Main article: Vacuum distillation
Some compounds have very high boiling points. To boil such compounds, it is
often better to lower the pressure at which such compounds are boiled instead of
increasing the temperature. Once the pressure is lowered to the vapor pressure
of the compound (at the given temperature), boiling and the rest of the
distillation process can commence. This technique is referred to as vacuum
distillation and it is commonly found in the laboratory in the form of the
rotary evaporator.
This technique is also very useful for compounds which boil beyond their
decomposition temperature at atmospheric pressure and which would therefore be
decomposed by any attempt to boil them under atmospheric pressure.
Molecular distillation is vacuum distillation below the pressure of 0.01
torr.[31] 0.01 torr is one order of magnitude above high vacuum, where fluids
are in the free molecular flow regime, i.e. the mean free path of molecules is
comparable to the size of the equipment. The gaseous phase no longer exerts
significant pressure on the substance to be evaporated, and consequently, rate
of evaporation no longer depends on pressure. That is, because the continuum
assumptions of fluid dynamics no longer apply, mass transport is governed by
molecular dynamics rather than fluid dynamics. Thus, a short path between the
hot surface and the cold surface is necessary, typically by suspending a hot
plate covered with a film of feed next to a cold plate with a clear line of
sight in between. Molecular distillation is used industrially for purification
of oils.
[edit] Air-sensitive vacuum distillation
Some compounds have high boiling points as well as being air sensitive. A simple
vacuum distillation system as exemplified above can be used, whereby the vacuum
is replaced with an inert gas after the distillation is complete. However, this
is a less satisfactory system if one desires to collect fractions under a
reduced pressure. To do this a "pig" adaptor can be added to the end of the
condenser, or for better results or for very air sensitive compounds a Perkin
triangle apparatus can be used.
The Perkin triangle, has means via a series of glass or Teflon taps to allows
fractions to be isolated from the rest of the still, without the main body of
the distillation being removed from either the vacuum or heat source, and thus
can remain in a state of reflux. To do this, the sample is first isolated from
the vacuum by means of the taps, the vacuum over the sample is then replaced
with an inert gas (such as nitrogen or argon) and can then be stoppered and
removed. A fresh collection vessel can then be added to the system, evacuated
and linked back into the distillation system via the taps to collect a second
fraction, and so on, until all fractions have been collected.
[edit] Short path distillation
Short path vacuum distillation apparatus with vertical condenser (cold finger),
to minimize the distillation path; 1: Still pot with stirrer bar/anti-bumping
granules 2: Cold finger - bent to direct condensate 3: Cooling water out 4:
cooling water in 5: Vacuum/gas inlet 6: Distillate flask/distillate.
Short path distillation is a distillation technique that involves the distillate
travelling a short distance, often only a few centimeters, and is normally done
at reduced pressure.[32] A classic example would be a distillation involving the
distillate travelling from one glass bulb to another, without the need for a
condenser separating the two chambers. This technique is often used for
compounds which are unstable at high temperatures or to purify small amounts of
compound. The advantage is that the heating temperature can be considerably
lower (at reduced pressure) than the boiling point of the liquid at standard
pressure, and the distillate only has to travel a short distance before
condensing. A short path ensures that little compound is lost on the sides of
the apparatus. The Kugelrohr is a kind of a short path distillation apparatus
which often contain multiple chambers to collect distillate fractions.
[edit] Other types
* The process of reactive distillation involves using the reaction vessel as the
still. In this process, the product is usually significantly lower-boiling than
its reactants. As the product is formed from the reactants, it is vaporized and
removed from the reaction mixture. This technique is an example of a continuous
vs. a batch process; advantages include less downtime to charge the reaction
vessel with starting material, and less workup.
* Pervaporation is a method for the separation of mixtures of liquids by partial
vaporization through a non-porous membrane.
* Extractive distillation is defined as distillation in the presence of a
miscible, high boiling, relatively non-volatile component, the solvent, that
forms no azeotrope with the other components in the mixture.
* Flash evaporation (or partial evaporation) is the partial vaporization that
occurs when a saturated liquid stream undergoes a reduction in pressure by
passing through a throttling valve or other throttling device. This process is
one of the simplest unit operations, being equivalent to a distillation with
only one equilibrium stage.
* Codistillation is distillation which is performed on mixtures in which the two
compounds are not miscible.
The unit process of evaporation may also be called "distillation":
* In rotary evaporation a vacuum distillation apparatus is used to remove bulk
solvents from a sample. Typically the vacuum is generated by a water aspirator
or a membrane pump.
* In a kugelrohr a short path distillation apparatus is typically used
(generally in combination with a (high) vacuum) to distill high boiling (> 300
°C) compounds. The apparatus consists of an oven in which the compound to be
distilled is placed, a receiving portion which is outside of the oven, and a
means of rotating the sample. The vacuum is normally generated by using a high
vacuum pump.
Other uses:
* Dry distillation or destructive distillation, despite the name, is not truly
distillation, but rather a chemical reaction known as pyrolysis in which solid
substances are heated in an inert or reducing atmosphere and any volatile
fractions, containing high-boiling liquids and products of pyrolysis, are
collected. The destructive distillation of wood to give methanol is the root of
its common name - wood alcohol.
* Freeze distillation is an analogous method of purification using freezing
instead of evaporation. It is not truly distillation, but a recrystallization
where the product is the mother liquor, and does not produce products equivalent
to distillation. This process is used in the production of ice beer and ice wine
to increase ethanol and sugar content, respectively. It is also used to produce
applejack. Unlike distillation, freeze distillation concentrates poisonous
congeners rather than removing them.
[edit] Azeotropic distillation
Main article: Azeotropic distillation
Interactions between the components of the solution create properties unique to
the solution, as most processes entail nonideal mixtures, where Raoult's law
does not hold. Such interactions can result in a constant-boiling azeotrope
which behaves as if it were a pure compound (i.e., boils at a single temperature
instead of a range). At an azeotrope, the solution contains the given component
in the same proportion as the vapor, so that evaporation does not change the
purity, and distillation does not effect separation. For example, ethyl alcohol
and water form an azeotrope of 95.6% at 78.1 °C.
If the azeotrope is not considered sufficiently pure for use, there exist some
techniques to break the azeotrope to give a pure distillate. This set of
techniques are known as azeotropic distillation. Some techniques achieve this by
"jumping" over the azeotropic composition (by adding an additional component to
create a new azeotrope, or by varying the pressure). Others work by chemically
or physically removing or sequestering the impurity. For example, to purify
ethanol beyond 95%, a drying agent or a (desiccant such as potassium carbonate)
can be added to convert the soluble water into insoluble water of
crystallization. Molecular sieves are often used for this purpose as well.
Immiscible liquids, such as water and toluene, easily form azeotropes. Commonly,
these azeotropes are referred to as a low boiling azeotrope because the boiling
point of the azeotrope is lower than the boiling point of either pure component.
The temperature and composition of the azeotrope is easily predicted from the
vapor pressure of the pure components, without use of Raoult's law. The
azeotrope is easily broken in a distillation set-up by using a liquid-liquid
separator ( a decanter ) to separate the two liquid layers that are condensed
overhead. Only one of the two liquid layers is refluxed to the distillation
set-up.
High boiling azeotropes, such as a 20 weight percent mixture of hydrochloric
acid in water, also exist. As implied by the name, the boiling point of the
azeotrope is greater than the boiling point of either pure component.
To break azeotropic distillations and cross distillation boundaries, such as in
the DeRosier Problem, it is necessary to increase the composition of the light
key in the distillate.
[edit] Breaking an azeotrope with unidirectional pressure manipulation
The boiling points of components in an azeotrope overlap to form a band. By
exposing an azeotrope to a vacuum or positive pressure, it's possible to bias
the boiling point of one component away from the other by exploiting the
differing vapour pressure curves of each; the curves may overlap at the
azeotropic point, but are unlikely to be remain identical further along the
pressure axis either side of the azeotropic point. When the bias is great
enough, the two boiling points no longer overlap and so the azeotropic band
disappears.
This method can remove the need to add other chemicals to a distillation, but it
has two potential drawbacks.
Under negative pressure, power for a vacuum source is needed and the reduced
boiling points of the distillates requires that the condenser be run cooler to
prevent distillate vapours being lost to the vacuum source. Increased cooling
demands will often require additional energy and possibly new equipment or a
change of coolant.
Alternatively, if positive pressures are required, standard glassware can not be
used, energy must be used for pressurization and there is a higher chance of
side reactions occurring in the distillation, such as decomposition, due to the
higher temperatures required to effect boiling.
A unidirectional distillation will rely on a pressure change in one direction,
either positive or negative.
[edit] Pressure-swing distillation
Further information: Pressure-Swing Distillation (section on the main Azeotrope
page)
This section may be confusing or unclear to readers. Please help clarify the
section; suggestions may be found on the talk page. (May 2009)
Pressure-swing distillation is essentially the same as the unidirectional
distillation used to break azeotropic mixtures, but here both positive and
negative pressures may be employed.[clarification needed]
This has an important impact on the selectivity of the distillation and allows a
chemist[citation needed] to optimize a process such that fewer extremes of
pressure and temperature are required and less energy is consumed. This is
particularly important in commercial applications.
Pressure-swing distillation is employed during the industrial purification of
ethyl acetate after its catalytic synthesis from ethanol.
[edit] Industrial distillation
Typical industrial distillation towers
Main article: Continuous distillation
Large scale industrial distillation applications include both batch and
continuous fractional, vacuum, azeotropic, extractive, and steam distillation.
The most widely used industrial applications of continuous, steady-state
fractional distillation are in petroleum refineries, petrochemical and chemical
plants and natural gas processing plants.
Industrial distillation[27][33] is typically performed in large, vertical
cylindrical columns known as distillation towers or distillation columns with
diameters ranging from about 65 centimeters to 16 meters and heights ranging
from about 6 meters to 90 meters or more. When the process feed has a diverse
composition, as in distilling crude oil, liquid outlets at intervals up the
column allow for the withdrawal of different fractions or products having
different boiling points or boiling ranges. The "lightest" products (those with
the lowest boiling point) exit from the top of the columns and the "heaviest"
products (those with the highest boiling point) exit from the bottom of the
column and are often called the bottoms.
Diagram of a typical industrial distillation tower
Large-scale industrial towers use reflux to achieve a more complete separation
of products. Reflux refers to the portion of the condensed overhead liquid
product from a distillation or fractionation tower that is returned to the upper
part of the tower as shown in the schematic diagram of a typical, large-scale
industrial distillation tower. Inside the tower, the downflowing reflux liquid
provides cooling and condensation of the upflowing vapors thereby increasing the
efficacy of the distillation tower. The more reflux that is provided for a given
number of theoretical plates, the better the tower's separation of lower boiling
materials from higher boiling materials. Alternatively, the more reflux that is
provided for a given desired separation, the fewer the number of theoretical
plates required.
Such industrial fractionating towers are also used in air separation, producing
liquid oxygen, liquid nitrogen, and high purity argon. Distillation of
chlorosilanes also enables the production of high-purity silicon for use as a
semiconductor.
Section of an industrial distillation tower showing detail of trays with bubble
caps
Design and operation of a distillation tower depends on the feed and desired
products. Given a simple, binary component feed, analytical methods such as the
McCabe-Thiele method[27][34] or the Fenske equation[27] can be used. For a
multi-component feed, simulation models are used both for design and operation.
Moreover, the efficiencies of the vapor-liquid contact devices (referred to as
"plates" or "trays") used in distillation towers are typically lower than that
of a theoretical 100% efficient equilibrium stage. Hence, a distillation tower
needs more trays than the number of theoretical vapor-liquid equilibrium stages.
In industrial uses, sometimes a packing material is used in the column instead
of trays, especially when low pressure drops across the column are required, as
when operating under vacuum.
Large-scale, industrial vacuum distillation column[35]
This packing material can either be random dumped packing (1-3" wide) such as
Raschig rings or structured sheet metal. Liquids tend to wet the surface of the
packing and the vapors pass across this wetted surface, where mass transfer
takes place. Unlike conventional tray distillation in which every tray
represents a separate point of vapor-liquid equilibrium, the vapor-liquid
equilibrium curve in a packed column is continuous. However, when modeling
packed columns, it is useful to compute a number of "theoretical stages" to
denote the separation efficiency of the packed column with respect to more
traditional trays. Differently shaped packings have different surface areas and
void space between packings. Both of these factors affect packing performance.
Another factor in addition to the packing shape and surface area that affects
the performance of random or structured packing is the liquid and vapor
distribution entering the packed bed. The number of theoretical stages required
to make a given separation is calculated using a specific vapor to liquid ratio.
If the liquid and vapor are not evenly distributed across the superficial tower
area as it enters the packed bed, the liquid to vapor ratio will not be correct
in the packed bed and the required separation will not be achieved. The packing
will appear to not be working properly. The height equivalent of a theoretical
plate (HETP) will be greater than expected. The problem is not the packing
itself but the mal-distribution of the fluids entering the packed bed. Liquid
mal-distribution is more frequently the problem than vapor. The design of the
liquid distributors used to introduce the feed and reflux to a packed bed is
critical to making the packing perform to it maximum efficiency. Methods of
evaluating the effectiveness of a liquid distributor to evenly distribute the
liquid entering a packed bed can be found in references.[36][37] Considerable
work as been done on this topic by Fractionation Research, Inc. (commonly known
as FRI).[38]
[edit] Distillation in food processing
[edit] Distilled beverages
Main article: Distilled beverage
Carbohydrate-containing plant materials are allowed to ferment, producing a
dilute solution of ethanol in the process. Spirits such as whiskey and rum are
prepared by distilling these dilute solutions of ethanol. Components other than
ethanol, including water, esters, and other alcohols, are collected in the
condensate, which account for the flavor of the beverage.
[edit] References
1. ^ Laurence M. Harwood, Christopher J. Moody (1990). Experimental organic
chemistry: Principles and Practice (Illustrated ed.). Oxford: Blackwell
Scientific Publications. pp. 141–143. ISBN 978-0632020171.
2. ^ Martin Levey (1956). "Babylonian Chemistry: A Study of Arabic and Second
Millennium B.C. Perfumery", Osiris 12, p. 376-389.
3. ^ a b Allchin 1979
4. ^ Forbes 1970: 53-54
5. ^ a b Colin Archibald Russell (2000). Chemistry, Society and Environment: A
New History of the British Chemical Industry. Royal Society of Chemistry. pp.
69. ISBN 0854045996.
6. ^ Edgar Ashworth Underwood. Science, Medicine, and History: Essays on the
Evolution of Scientific Thought and Medical. Oxford University Press. pp. 251.
7. ^ a b Charles Simmonds (1919). Alcohol: With Chapters on Methyl Alcohol,
Fusel Oil, and Spirituous Beverages. Macmillan and Co. Ltd. pp. 6.
8. ^ Distillation - LoveToKnow 1911
9. ^ Biology, Joan Solomon, Pat O'Brien, Peter Horsfall, Nelson Thornes, p.41
10. ^ Robert Briffault (1938), The Making of Humanity, p. 195:
"Chemistry, the rudiments of which arose in the processes employed by Egyptian
metallurgists and jewellers combining metals into various alloys and 'tinting'
them to resemble gold processes long preserved as a secret monopoly of the
priestly colleges, and clad in the usual mystic formulas, developed in the hands
of the Arabs into a widespread, organized passion for research which led them to
the invention of pure distillation, sublimation, filtration, to the discovery of
alcohol, of nitric and sulfuric acids (the only acid known to the ancients was
vinegar), of the alkalis, of the salts of mercury, of antimony and bismuth, and
laid the basis of all subsequent chemistry and physical research."
11. ^ Microscale Laboratory Techniques - Distillation from McMaster University
12. ^ Hassan, Ahmad Y. "Alcohol and the Distillation of Wine in Arabic Sources".
History of Science and Technology in Islam.
http://www.history-science-technology.com/Notes/Notes%207.htm. Retrieved
2008-03-29.
13. ^ Kasem Ajram (1992). Miracle of Islamic Science. Knowledge House
Publishers. Appendix B. ISBN 0911119434.
14. ^ A. Wolf, G. A. Bray, B. M. Popkin (2007). "A short history of beverages
and how our body treats them". Obesity Reviews 9: 151.
doi:10.1111/j.1467-789X.2007.00389.x.
15. ^ a b Forbes 1970: 42
16. ^ Forbes 1970: 45
17. ^ Forbes 1970: 54
18. ^ Hassan, Ahmad Y. "Technology Transfer in the Chemical Industries". History
of Science and Technology in Islam.
http://www.history-science-technology.com/Articles/articles%2072.htm. Retrieved
2008-03-29.
19. ^ Magnum Opus Hermetic Sourceworks Series
20. ^ Industrial Engineering Chemistry (1936) page 677
21. ^ Sealing Technique, accessed 16 November 2006.
22. ^ Traditional Alembic Pot Still, accessed 16 November 2006.
23. ^ a b D. F. Othmer (1982) Distillation - Some Steps in its Development, in
W. F. Furter (ed) A Century of Chemical Engineering ISBN 0-306-40895-3
24. ^ A. Coffey British Patent 5974, 5 August 1830
25. ^ U.S. Patent 198,699 Improvement in the Ammonia-Soda Manufacture
26. ^ ST07 Separation of liquid - liquid mixtures (solutions), DIDAC by IUPAC
27. ^ a b c d Perry, Robert H. and Green, Don W. (1984). Perry's Chemical
Engineers' Handbook (6th ed.). McGraw-Hill. ISBN 0-07-049479-7.
28. ^ Fractional Distillation
29. ^ Spinning Band Distillation at B/R Instrument Corporation (accessed 8
September 2006)
30. ^ Laurence M. Harwood, Christopher J. Moody (1989). Experimental organic
chemistry: Principles and Practice (Illustrated ed.). Wiley, Blackwell. pp.
151–153. ISBN 978-0632020171.
31. ^ Vogel's 5th ed.
32. ^ Laurence M. Harwood, Christopher J. Moody (13 Jun 1989). Experimental
organic chemistry: Principles and Practice (Illustrated ed.). Wiley, Blackwell.
pp. 150. ISBN 978-0632020171.
33. ^ Kister, Henry Z. (1992). Distillation Design (1st ed.). McGraw-Hill. ISBN
0-07-034909-6.
34. ^ Seader, J. D., and Henley, Ernest J. (1998). Separation Process
Principles. New York: Wiley. ISBN 0-471-58626-9.
35. ^ Energy Institute website page
36. ^ Random Packing, Vapor and Liquid Distribution: Liquid and gas distribution
in commercial packed towers, Moore, F., Rukovena, F., Chemical Plants &
Processing, Edition Europe, August 1987, p. 11-15
37. ^ Spiegel, L (2006). "A new method to assess liquid distributor quality".
Chemical Engineering and Processing 45: 1011. doi:10.1016/j.cep.2006.05.003.
38. ^ Packed Tower Distributors: Commercial Scale Experiments That Provide
Insight on Packed Tower Distributors, Kunesh, J. G., Lahm, L., Yanagi, T., Ind.
Eng. Chem. Res., 1987, vol. 26, p. 1845-1850 doi:10.1021/ie00069a021 FRI (click
on "Available Materials" and scroll to "Staff Publications")
[edit] Further reading
* Forbes, R. J. (1970). A Short History of the Art of Distillation from the
Beginnings up to the Death of Cellier Blumenthal. BRILL. ISBN 9004006176.
http://books.google.com/books?id=XeqWOkKYn28C&printsec=frontcover.
* Needham, Joseph (1980). Science and Civilisation in China Cambridge University
Press: ISBN 052108573X
* Allchin, F. R. (Mar., 1979). India: The Ancient Home of Distillation?. Man,
New Series, Vol. 14, No. 1, pp. 55–63. Royal Anthropological Institute of Great
Britain and Ireland.
[edit] Gallery
Retort-in-operation-early-chemistry.PNG Chemistry on its beginnings used retorts
as laboratory equipment exclusively for distillation processes.
Distillation of dry and oxygen-free toluene.jpg A simple set-up to distill dry
and oxygen-free toluene.
Vacuum Column.png Diagram of an industrial-scale vacuum distillation column as
commonly used in oil refineries
Rotavapor.jpg A rotary evaporator is able to distill solvents more quickly at
lower temperatures through the use of a vacuum.
Semi-microscale distillation.jpg Distillation using semi-microscale apparatus.
The jointless design eliminates the need to fit pieces together. The pear-shaped
flask allows the last drop of residue to be removed, compared with a
similarly-sized round-bottom flask The small holdup volume prevents losses. A
pig is used to channel the various distillates into three receiving flasks. If
necessary the distillation can be carried out under vacuum using the vacuum
adapter at the pig.
[edit] External links
Search Wiktionary Look up distillation in Wiktionary, the free dictionary.
Search Wikimedia Commons Wikimedia Commons has media related to: Distillation
* Alcohol distillation
* Case Study: Petroleum Distillation
* "Binary Vapor-Liquid Equilibrium Data" (searchable database). Chemical
Engineering Research Information Center.
http://www.cheric.org/research/kdb/hcvle/hcvle.php. Retrieved 5 May 2007.
[show]
v • d • e
Distillation
Principles
Raoult's law · Dalton's law · Reflux · Fenske equation · McCabe-Thiele method ·
Theoretical plate · Partial pressure · Vapor-liquid equilibrium
Simple distillation apparatus
Industrial processes
Batch distillation · Continuous distillation · Fractionating column · Spinning
cone
Laboratory methods
Alembic · Kugelrohr · Rotary evaporator · Spinning band distillation · Still
Techniques
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82. [PDF]
ESSENTIAL OILS
File Format: PDF/Adobe Acrobat - Quick View
chosen as materials to prepare the essential oils. The yield of essential oil
was determined. ... The efficacy of plant essential oils (EOs) for control ...
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83.
How to Make Essential Oils - wikiHow
2 Dec 2009 ... Essential oils are highly concentrated, volatile oils that can be
extracted from aromatic plants. Their use dates back to ancient times, ...
www.wikihow.com/Make-Essential-Oils -
84.
THE ESSENTIAL OIL MARKET
by EW Bovux
ESSENTIAL oils are mostly the products of tropical and sub-tropical countries.
... the only African country exporting essential oils was Algeria, ...
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85.
Physic al properties of some spice essential oils and flavourants
Major essential oils - their production and adulterants. Essential oil. Origin.
Major. Countries. Adulterants employed. Bergamot oil. Cassia oil ...
www.indianspices.com/pdf/phys_prop.pdf - Similar
86.
How to Use Essential Oils for Perfumed Pillows | eHow.com
How to Use Essential Oils for Perfumed Pillows. Most people have sleep disorders
at one time or another throughout their lives. They can range from insomnia ...
www.ehow.com › ... › Alternative Medicine › Aromatherapy - Cached
87.
People in Essential Oils - Oilganic
Essential Oils Knowledge - Find people in essential oils, ... OUR GOAL: Simply
everything you need on essential oils and herbs in one easy to find place. ...
oilganic.com/ -
88.
Essential oils,Aromatherapy essential oils,Essential oil ...
Essential oils and aromatics - updated online directory of Indian and global
essential oil manufacturers,essential oil suppliers,essential oils and ...
www.tradeindia.com › ... › Health & Beauty › Essential Oils & Aromatics - Cached
89.
The complete book of essential oils and aromatherapy - Google Books Result
Valerie Ann Worwood - 1991 - Health & Fitness - 423 pages
This complete volume explains how to incorporate these ancient medicines of the
earth into everyday life for personal care, physical and mental health, and a
...
books.google.co.in/books?isbn=0931432820...
90.
Guide to Aromatherapy and Aromatherapy Essential Oils
A best online guide to buy aromatic products. It helps you to find useful
information on aromatherapy.
www.aromacures.com/ -
91.
Essential Oils Exporters,Pure Essential Oils Exporter,Essential ...
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92.
Essential Oils: Descriptions, Profiles & Uses
Cedarwood, Red - Red cedarwood essential oil actually comes from a type of .....
Patchouli oil is one of the few essential oils that improve with age. ...
www.auracacia.com › Home › Learn -
93.
Essential Oils
Essential oils is a kind of are the subtle, aromatic and volatile liquids
extracted from the flowers, seeds, leaves, stems, bark and roots of herbs,
bushes, ...
www.experiencefestival.com/essential_oil -
94.
Essential Oils in Nepal : A Practical Guide to Essential Oils and ...
Chemistry of essential oils. Part II: 1. Extraction methods of essential oils.
... Quality control of essential oils. 2. Analysis and quality assessment. 3.
...
www.vedamsbooks.com/no64457.htm - Cached
95.
Doterra Blog - How to Use Essential Oils - The Essential Oil How ...
Well, I was able to sleep through the night with your essential oils! I honestly
believe in doTerra's oils! After the first drop on my hand, I noticed how ...
doterrablog.com/ -
96.
Essential oils have been found to kill the deadly MRSA bacteria
Essential oils usually used in aromatherapy have been found to kill the ...
Tests revealed that three essential oils killed MRSA and E. coli as well as many
...
www.news-medical.net/news/2004/12/21/6975.aspx -
97.
Aromatherapy Products, Aromatherapy Oils
There are well over a hundred different essential oils with antiseptic
properties. ... Incense is typically made with essential oils from plants. ...
www.scentsiblearoma.com/ -
98.
Lark's Essential Oils, Soaps and Herbs
Organic essential and massage oils, supplements, teas, soaps, and candles.
www.larksherbs.com/ -
99.
Aromatherapy: Guidelines for Using Essential Oils and Herbs
Because essential oils are concentrated, highly potent substances, ... The
potential hazards of an essential oil depend on the compounds in the oil, ...
www.healthy.net/scr/article.aspx?ID=1711 - Cached
100.
Organic Herbs, Essential Oils, Pagan Wiccan Supplies, Natural ...
15 Dec 2009 ... The place for wiccan pagan supplies, renaissance clothing,
organic herbs and essential oils, natural products for home, garden and health.
www.herbalmusings.com/ -
101.
Therapeutic grade essential oils, shea body butter, aromatherapy ...
Offering wild-crafted essential oils, perfumes, skin care, gift sets, and bulk
natural ingredients.
www.lunaroma.com/ -
102.
Blog posts about Essential Oils
» The essential oils Health, Wellness, Beauty, Skin Care - Health, Wellness,
Beauty, Skin Care - 13 hours ago
MAC Care Blends Essential Oils - Beauty Trends and News ... - DailyMakeover Home
- 2 Mar 2010
Buying essential oils: 3 important things you need to look for ... - Essential
Oil Botanicals - 1 day ago
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