Emulsion 10290 225738661 2008-07-15T04:20:33Z 98.212.213.235 /* Emulsifier */ [[Image:Emulsions.svg|frame|right|A. Two immiscible liquids, not yet emulsified; B. An emulsion of Phase II dispersed in Phase I; C. The unstable emulsion progressively separates; D. The surfactant (purple outline) positions itself on the interfaces between Phase II and Phase I, stabilizing the emulsion]] An '''emulsion''' ([[IPA]]: /ɪˈmʌlʃən/<ref>[http://dictionary.reference.com/browse/Emulsion Emulsion - Definitions from Dictionary.com<!-- Bot generated title -->]</ref>) is a mixture of two [[immiscible]] (unblendable) substances. One substance (the dispersed [[Phase (matter)|phase]]) is [[dispersion|dispersed]] in the other (the continuous [[Phase (matter)|phase]]). Examples of emulsions include [[butter]] and [[margarine]], [[milk]] and cream, [[espresso]], [[mayonnaise]], the photo-sensitive side of [[photographic film]], [[magma]]s and [[cutting fluid]] for [[metal working]]. In butter and margarine, oil surrounds droplets of water (a water-in-oil emulsion). In milk and cream, water surrounds droplets of oil (an oil-in-water emulsion). In certain types of magma, globules of liquid [[NiFe]] may be dispersed within a continuous phase of liquid [[silicate]]s. Emulsification is the process by which emulsions are prepared. Emulsion is also a term used in the [[oil field]] as untreated [[oil well|well]] production that consists primarily of [[crude oil]] and water. ==Operation== Emulsions tend to have a cloudy appearance, because the many [[phase boundary|phase interfaces]] (the boundary between the phases is called the interface) [[scattering|scatter]] light that passes through the emulsion. Emulsions are unstable and thus do not form spontaneously. Energy input through shaking, stirring, homogenizers, or spray processes are needed to form an emulsion. Over time, emulsions tend to revert to the stable state of oil separated from water. Surface active substances ([[surfactant]]s) can increase the kinetic stability of emulsions greatly so that, once formed, the emulsion does not change significantly over years of storage. Homemade [[cooking oil|oil]] and [[vinegar]] [[salad dressing]] is an example of an unstable emulsion that will quickly separate unless shaken continuously. This phenomenon is called [[coalescence (meteorology)|coalescence]], and happens when small droplets recombine to form bigger ones. Fluid emulsions can also suffer from [[creaming (chemistry)|creaming]], the migration of one of the substances to the top of the emulsion under the influence of [[buoyancy]] or [[centripetal force]] when a [[centrifuge]] is used. Emulsions are part of a more general class of two-phase systems of matter called [[colloid]]s. Although the terms colloid and emulsion are sometimes used interchangeably, emulsion tends to imply that both the dispersed and the continuous phase are [[liquid]]. There are three types of emulsion instability: [[flocculation]], where the particles form clumps; [[creaming]], where the particles concentrate towards the surface (or bottom, depending on the relative density of the two phases) of the mixture while staying separated; and breaking and [[coalescence]] where the particles coalesce and form a layer of liquid. ==Emulsifier== <!-- This section is linked from [[Solution]] --> {{unreferencedsection|date=July 2008}} An emulsifier (also known as an emulgent) is a substance which stabilizes an emulsion, frequently a [[surfactant]]. Examples of food emulsifiers are [[egg yolk]] (where the main emulsifying chemical is [[lecithin]]), honey and [[mustard seed|mustard]], where a variety of chemicals in the [[mucilage]] surrounding the seed hull act as emulsifiers; [[protein]]s and low-molecular weight emulsifiers are common as well. In some cases, particles can stabilize emulsions as well through a mechanism called [[Pickering emulsion|Pickering stabilization]]. Both [[mayonnaise]] and [[hollandaise sauce]] are oil-in-water emulsions that are stabilized with egg yolk lecithin. [[Detergent]]s are another class of surfactant, and will chemically interact with both [[cooking oil|oil]] and [[water]], thus stabilising the interface between oil or water droplets in suspension. This principle is exploited in [[soap]] to remove [[yellow grease|grease]] for the purpose of [[cleaning]]. A wide variety of emulsifiers are used in [[pharmacy]] to prepare emulsions such as [[cream (pharmaceutical)|creams]] and [[lotion]]s. [[Image:propofol.jpg|left|thumb|20 ml ampule of 1% [[propofol]] emulsion suitable for [[intravenous]] injection. The manufacturers emulsify the lipid soluble propofol in a mixture of water, soy oil and egg [[lecithin]].]] Whether an emulsion turns into a water-in-oil emulsion or an oil-in-water emulsion depends on the volume fraction of both phases and on the type of emulsifier. Generally, the [[Bancroft rule]] applies: emulsifiers and emulsifying particles tend to promote dispersion of the phase in which they do not dissolve very well; for example, proteins dissolve better in water than in oil and so tend to form oil-in-water emulsions (that is they promote the dispersion of oil droplets throughout a continuous phase of water). ==Nanoemulsion== {{unreferencedsection|date=March 2008}} '''Nanoemulsion''' is a type of [[emulsion]] in which the sizes of the particles in the dispersed phase are defined as less than 1000 [[nanometers]]. In medicine, a nanoemulsion of [[soybean oil]] to create drops of 400-600 nanometers in diameter will kill many [[pathogens]] such as bacteria and viruses.<ref>http://www.eurekalert.org/pub_releases/2008-02/uomh-nvs022608.php, accessed April 09, 2008</ref> The process is not chemical, as with other types of anti-pathogenic treatments, but physical. The smaller the droplet, the greater the [[surface tension]] and thus the greater the force to merge with other [[lipids]]. The oil is emulsified with detergents to stabilize the emulsion (the droplets won't merge with one another), so when they encounter lipids on a bacterial membrane or a [[virus|virus envelope]], they force the lipids to merge with themselves. On a mass scale, this effectively disintegrates the membrane and kills the pathogen. Remarkably, the soybean oil emulsion does not harm normal human cells nor the cells of most other higher organisms. The exceptions are [[Spermatozoon|sperm cells]] and [[blood cells]], which are vulnerable to nanoemulsions due to their membrane structures. For this reason, nanoemulsions of this type are not yet ready to be used [[intravenous]]ly. The most effective application of this type of nanoemulsion is for the disinfection of surfaces. Some types of nanoemulsions have been shown to effectively destroy [[HIV-1]] and various [[tuberculosis]] pathogens, for example, on non-porous surfaces. ==See also== * [[Amphiphile]] * [[Photo emulsion]] * [[Water-in-water emulsion]] * [[Photographic emulsion]] * [[Interface and colloid science]] ==References== <references/> == External links == * [http://logikbase.com/website/techprofile.cfm?licid=1084 Microfluidic Production of Monodispersed Submicron EmulsionsThrough Filtration and Sorting of Satellite Drops 2005-652] * [http://www.micropore.co.uk/emulsion_video.html Video images of the process of membrane emulsification] * [http://www.nanomi.nl/Downloads/droplets.wmv Video image of monodisperse droplets produced by membrane emulsification] * [http://www.nanomi.com/ Company website of Nanomi, specialized in membrane emulsification] * [http://www.microporetech.com/membrane_emulsification.html Explanation of the process of membrane emulsification] * [http://www.medicineatmichigan.org/magazine/2000/summer/nanonman/default.asp Medicine at Michigan] * [http://www.nanotech-now.com/Jose-Feneque/Veterinary-Applications-Nanotechnology.htm Veterinary Applications] * [http://www.dispersion.com/ Dispersion Technology] [[Category:Chemical mixtures]] [[Category:Colloidal chemistry]] [[Category:Condensed matter physics]] [[Category:Matter]] [[Category:Soft matter]] [[bs:Emulzija]] [[bg:Емулсия]] [[ca:Emulsió]] [[cs:Emulze]] [[da:Emulsion]] [[de:Emulsion]] [[et:Emulsioon]] [[es:Emulsión]] [[fr:Émulsion]] [[gl:Emulsión]] [[hr:Emulzija]] [[id:Emulsi]] [[it:Emulsione]] [[he:חומר מתחלב]] [[lt:Emulsija]] [[mk:Емулзија]] [[ms:Emulsi]] [[nl:Emulsie]] [[ja:エマルション]] [[no:Emulsjon]] [[pl:Emulsja]] [[pt:Emulsão]] [[ro:Emulsie]] [[ru:Эмульсия]] [[sl:Emulzija]] [[sr:Емулзија]] [[sh:Emulzija]] [[fi:Emulsio]] [[sv:Emulsion]] [[th:อิมัลชัน]] [[vi:Nhũ tương]] [[tr:Emülsiyon]] [[uk:Емульсія]] [[zh:乳剂]]