Editing Colloid (section)

{{Short description|Mixture of an insoluble substance microscopically dispersed throughout another substance}}
[[File:SEM Image of Colloidal Particles.jpg|thumb|upright=1.2|[[Scanning electron microscope|SEM]] image of a colloid.]]
{{Use dmy dates|date=March 2021}}
{{Condensed matter physics}}
A '''colloid''' is a [[mixture]] in which one substance consisting of microscopically [[Dispersion (chemistry)|dispersed]] [[insoluble]] [[particle]]s is [[suspension (chemistry)|suspended]] throughout another substance. Some definitions specify that the particles must be dispersed in a [[liquid]],<ref name="Israelachvili-2011">{{Cite book |last=Israelachvili |first=Jacob N. |title=Intermolecular and surface forces |date=2011 |publisher=Academic Press |isbn=978-0-08-092363-5|edition=4rd |location=Burlington, MA |oclc=706803091}}</ref> while others extend the definition to include substances like [[aerosol]]s and [[gel]]s. The term '''colloidal suspension''' refers unambiguously to the overall mixture (although a narrower sense of the word ''[[suspension (chemistry)|suspension]]'' is distinguished from colloids by larger particle size). A colloid has a dispersed phase (the suspended particles) and a continuous phase (the medium of suspension). The dispersed phase particles have a diameter of approximately 1 [[nanometre]] to 1 [[micrometre]].<ref>{{Cite book|author1=International Union of Pure and Applied Chemistry. Subcommittee on Polymer Terminology|url=https://www.worldcat.org/oclc/406528399|title=Compendium of polymer terminology and nomenclature : IUPAC recommendations, 2008|date=2009|publisher=Royal Society of Chemistry|author2=Jones, Richard G. |isbn=978-1-84755-942-5|location=Cambridge|oclc=406528399}}</ref><ref>{{Cite journal|last=Stepto|first=Robert F. T.|date=2009-01-01|title=Dispersity in polymer science (IUPAC Recommendations 2009)|journal=Pure and Applied Chemistry|volume=81|issue=2|pages=351–353|doi=10.1351/PAC-REC-08-05-02|s2cid=95122531|doi-access=free}}</ref>

Some colloids are [[translucent]] because of the [[Tyndall effect]], which is the [[scattering]] of light by particles in the colloid. Other colloids may be [[Opacity (optics)|opaque]] or have a slight color.

Colloidal suspensions are the subject of [[interface and colloid science]]. This field of study began in 1845 by [[Francesco Selmi]],<ref>Selmi, Francesco "Studi sulla dimulsione di cloruro d'argento". ''Nuovi Annali delle Scienze Naturali di Bologna, 1845''.</ref><ref>Selmi, Francesco, Studio intorno alle pseudo-soluzioni degli azzurri di Prussia ed alla influenza dei sali nel guastarle, Bologna: Tipi Sassi, 1847</ref><ref>Hatschek, Emil, The Foundations of Colloid Chemistry, A selection of early papers bearing on the subject, The British Association Committee on Colloid Chemistry, London, 1925</ref><ref>Selmi, Francesco - Sur le soufre pseudosoluble, sa pseudosolution e le soufre mou, Journal de Pharmacie et de Chimie, tome 21, 1852, Paris</ref> who called them pseudosolutions, and expanded by [[Michael Faraday]]<ref>{{cite journal|doi=10.1162/posc.2006.14.1.97|title=Discovering Discovery: How Faraday Found the First Metallic Colloid |year=2006 |last1=Tweney |first1=Ryan D. |journal=Perspectives on Science |volume=14 |pages=97–121 |s2cid=55882753 }}</ref> and [[Thomas Graham (chemist)|Thomas Graham]], who coined the term ''colloid'' in 1861.<ref>{{cite journal|doi=10.1098/rstl.1861.0011|title=X. Liquid diffusion applied to analysis |journal=Philosophical Transactions of the Royal Society of London |year=1861 |volume=151 |pages=183–224 |s2cid=186208563 }}.  Page 183:  "As gelatine appears to be its type, it is proposed to designate substances of the class as ''colloids'', and to speak of their peculiar form of aggregation as the ''colloidal condition of matter''."</ref>{{Quote box
| title = [[IUPAC]] definition
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| quote = '''Colloid''': Short synonym for ''colloidal'' system.<ref name=quote1>{{cite book|title=Compendium of Polymer Terminology and Nomenclature (IUPAC Recommendations 2008)|year=2009|publisher=RSC Publ.|isbn=978-0-85404-491-7|pages=464|edition= 2nd|editor1=Richard G. Jones |editor2=Edward S. Wilks |editor3=W. Val Metanomski |editor4=Jaroslav Kahovec |editor5=Michael Hess |editor6=Robert Stepto |editor7=Tatsuki Kitayama }}</ref><ref name=quote2>{{cite journal|title=Dispersity in polymer science (IUPAC Recommendations 2009)|journal=[[Pure and Applied Chemistry]]|year=2009|volume=81|issue=2|pages=351–353|doi=10.1351/PAC-REC-08-05-02|url=http://pac.iupac.org/publications/pac/pdf/2009/pdf/8102x0351.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://pac.iupac.org/publications/pac/pdf/2009/pdf/8102x0351.pdf |archive-date=2022-10-09 |url-status=live|last1=Stepto|first1=Robert F. T.|s2cid=95122531}}</ref>

'''Colloidal''': State of subdivision such that the molecules or polymolecular particles dispersed in a medium have at least one dimension between approximately 1 nm and 1 μm, or that in a system discontinuities are found at distances of that order.<ref name=quote1 /><ref name=quote2 /><ref>{{cite journal|title=Terminology of polymers<br/>and polymerization processes in dispersed systems (IUPAC Recommendations 2011)|journal=[[Pure and Applied Chemistry]]|year=2011|volume=83|issue=12|pages=2229–2259|doi=10.1351/PAC-REC-10-06-03|url=http://pac.iupac.org/publications/pac/pdf/2011/pdf/8312x2229.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://pac.iupac.org/publications/pac/pdf/2011/pdf/8312x2229.pdf |archive-date=2022-10-09 |url-status=live|last1=Slomkowski|first1=Stanislaw|last2=Alemán|first2=José V.|last3=Gilbert|first3=Robert G.|last4=Hess|first4=Michael|last5=Horie|first5=Kazuyuki|last6=Jones|first6=Richard G.|last7=Kubisa|first7=Przemyslaw|last8=Meisel|first8=Ingrid|last9=Mormann|first9=Werner|last10=Penczek|first10=Stanisław|last11=Stepto|first11=Robert F. T.|s2cid=96812603}}</ref>
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