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136:(i.e., a uniform substance that has the same composition throughout the material). The perfect pure chemical will pass all attempts to separate and purify it further. Thirdly, and here we focus on the common chemical definition, it should not contain any trace of any other kind of chemical species. In reality, there are no absolutely 100% pure chemical compounds, as there is always some small amount of
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297:, the elements added to the original crystal structure, contain a different number of electrons then the base formula. Semiconductors that are p-doped contains a small amount of elements that have less valence electrons then the other elements in the crystal. N-doping is the opposite and the dopant contains more valence electrons.
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to acquire certain properties of a material such as the color in gemstones or conductivity in semiconductors. Impurities may also affect crystallization as they can act as nucleation sites that start crystal growth. Impurities can also play a role in nucleation of other phase transitions in the form of defects.
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of a chemical or commercial product. During production, impurities may be purposely or accidentally added to the substance. The removal of unwanted impurities may require the use of separation or purification techniques such as distillation or zone refining. In other cases, impurities might be added
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No matter what method is used, it is usually impossible to separate an impurity completely from a material. The reason that it is impossible to remove impurities completely is of thermodynamic nature and is predicted by the second law of thermodynamics. Removing impurities completely means reducing
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Occasionally, we may want to include impurities in a material to change its properties. These impurities can be naturally occurring and left unaltered in a material or be intentionally added during synthesis. These types of impurities can show up in our day-to-day lives such as different colors in
215:. This is done by heating the water so it boils and leaves behind the salt. The water is cooled and the gas turns back to a pure liquid. Impurities are usually physically removed from liquids and gases. Removal of sand particles from metal ore is one example with solids.
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Impurities in pharmaceuticals and therapeutics are of special concern and the last couple of decades have witnessed a fair number of scandals, from insecure ingredients and incorrect dosage forms to intentionally fortified medications and accidental contaminations.
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have been established by various organizations that attempt to define the permitted levels of various impurities in a manufactured product. Strictly speaking, a material's level of purity can only be stated as being more or less pure than some other material.
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Impurities play an important role in the nucleation of other phase transitions. For example, the presence of foreign elements may have important effects on the mechanical and magnetic properties of metal alloys. Iron atoms in copper cause the renowned
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below its melting point without becoming a solid. This occurs because the liquid has nothing to condense around so the solid cannot form a natural crystalline solid. The solid is eventually formed when
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of a new phase is lower at a point defect. In order for the nucleus of a new phase to be stable, it must reach a critical size. This threshold size is often lower at an impurity site.
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and leaf pieces in blank white papers. The removal of impurities is usually done chemically. For example, in the manufacturing of
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around the impurities and becomes a crystalline solid. If there are no impurities then the liquid is said to be pure and can be
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Urwin, Stephanie J.; Levilain, Guillaume; Marziano, Ivan; Merritt, Jeremy M.; Houson, Ian; Ter Horst, Joop H. (2020-08-21).
263:. Pure beryl will appear colorless but this rarely occurs and the presence of trace elements change its color. The green of
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is a process where impurities are purposefully added to semiconductors to increase electrical conductivity and improve a
223:. What technicians can do is to increase the purity of a material to as near 100% as possible or economically feasible.
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where the conduction electron spins form a magnetic bound state with the impurity atom. Magnetic impurities in
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Impurities can become unwanted when they prevent the working nature of the material. Examples include ash and
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192:, another purification method, is an economically important method for the purification of semiconductors.
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are from impurities such as chromium, vanadium, or iron. A manganese impurity will give a pink gem called
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their concentration to zero. This would require an infinite amount of work and energy as predicted by the
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An example of when impurities are wanted is shown in gems. These gems have slight impurities that act as
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643:"A Structured Approach To Cope with Impurities during Industrial Crystallization Development"
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However, some kinds of impurities can be removed by physical means. A mixture of water and
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of the material or compound. Firstly, a pure chemical should appear in at least one
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The levels of impurities in a material are generally defined in relative terms.
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Distillation
Control, Optimization, and Tuning: Fundamentals and Strategies
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518:"Chemical Impurities: An Epistemological Riddle with Serious Side Effects"
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Substance within a material that differs from its chemical composition
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gemstones or by doping to tune the conductivity of semiconductors.
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Abdin, Ahmad Yaman; Yeboah, Prince; Jacob, Claus (February 2020).
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International
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and give the stone its color. An example is the gem family
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Impurities are either naturally occurring or added during
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defects. Point defects can nucleate reversed domains in
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Three gems from the beryl family with different colors.
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because the energetic cost of creating a finite-size
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132:. Secondly, a pure chemical should prove to be
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580:"Gem-Stones and Their Distinctive Characters"
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647:Organic Process Research & Development
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247:witch has the base chemical formula of Be
80:Learn how and when to remove this message
855:List of medicine contamination incidents
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43:This article includes a list of general
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305:When an impure liquid is cooled to its
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128:and can also be characterized by its
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354:can serve as generation sites for
49:it lacks sufficient corresponding
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830:Counterfeit illegal drug selling
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698:Chemistry – A Modern View
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362:and dramatically affect their
271:and iron creates the blue gem
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609:Doping in Conjugated Polymers
478:Robbins, Lanny (2011-05-27).
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330:occurs, but it forms into an
221:second law of thermodynamics
108:inside a confined amount of
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454:"Definition of HOMOGENEOUS"
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199:A basic distillation set up
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762:Combined drug intoxication
606:Kar, Pradip (2013-08-23).
338:, instead, as there is no
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484:. Boca Raton: CRC Press.
309:the liquid, undergoing a
301:Impurities and nucleation
794:Polysubstance dependence
659:10.1021/acs.oprd.0c00166
429:"Definition of IMPURITY"
916:Environmental chemistry
850:Counterfeit medications
458:www.merriam-webster.com
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120:. They differ from the
64:more precise citations.
740:Combined substance use
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612:(1 ed.). Wiley.
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160:Unwanted impurities
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846:Medicines
822:Drug fraud
589:2024-04-15
464:2024-03-27
439:2024-04-01
415:References
364:coercivity
273:aquamarine
180:to remove
102:impurities
45:references
911:Materials
667:1083-6160
544:1661-7827
409:Spin wave
394:Pollution
269:morganite
184:from the
153:synthesis
145:Standards
94:chemistry
862:Impurity
789:Polypill
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389:Fineness
378:See also
265:emeralds
186:iron ore
18:Impurity
804:Synergy
799:Prodrug
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213:residue
58:improve
840:Lacing
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287:Doping
170:metals
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110:liquid
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118:solid
116:, or
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