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			{{short description|Synthetic pigment}}
	{{about|the pigment|the musical duo|Prussian Blue}}
			{{About|the pigment}}
			{{Distinguish|Russian Blue|Persian blue}}
			{{redirect|Paris Blue|the Kyle Eastwood album|Paris Blue (album)}}
	{{Chembox		{{Chembox
	| Verifiedfields = changed		| Verifiedfields = changed
	| Watchedfields = changed		| Watchedfields = changed
	| verifiedrevid = 396539636		| verifiedrevid = 464375726
	| ImageFile =		| Name =
			| ImageFile = Pigment Berliner Blau.JPG
	| ImageFile_Ref = {{Chemboximage|correct|??}}		| ImageFile_Ref = {{Chemboximage|correct|??}}
	| ImageSize =		| ImageSize = 220
	| ImageName = Sample of prussian blue		| ImageName = Sample of prussian blue
	| IUPACName = Iron(II,III) hexacyanoferrate(II,III)		| IUPACName = Iron(II,III) hexacyanidoferrate(II,III)
	| SystematicName = <!-- Iron(3+) hexacyanoirontetrauide (substitutive) OR Iron(3+) hexacyanidoferrate(4-) (additive)-->		| SystematicName = <!-- Iron(3+) hexacyanoirontetrauide (substitutive) OR Iron(3+) hexacyanidoferrate(4-) (additive)-->
	| OtherNames = Berlin blue<br />		| OtherNames = {{ubl
			|Brandenburg blue
	Ferric ferrocyanide<br />
			|Berlin blue
	Ferric hexacyanoferrate<br />
			|Ferric ferrocyanide
	Iron(III) ferrocyanide<br />
			|Ferric hexacyanoferrate
	Iron(III) hexacyanoferrate(II)<br />
			|Iron(III) ferrocyanide
	Parisian blue
			|Iron(III) hexacyanoferrate(II)
			|Parisian blue
			|Sarum blue
			|Midnight blue
			}}
	| Section1 = {{Chembox Identifiers		| Section1 = {{Chembox Identifiers
	| InChI = 1S/18CN.7Fe/c18*1-2;;;;;;;/q;;;;;;;;;;;;;;;;;;3*-4;4*+3		| InChI = 1S/18CN.7Fe/c18*1-2;;;;;;;/q;;;;;;;;;;;;;;;;;;3*-4;4*+3
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	| CASNo_Ref = {{cascite|correct|CAS}}		| CASNo_Ref = {{cascite|correct|CAS}}
	| PubChem = 2724251		| PubChem = 2724251
			| ChEMBL_Ref = {{ebicite|changed|EBI}}
	| ChEMBL = <!-- blanked - oldvalue: 1200325 -->
			| ChEMBL = 2096629
	| PubChem_Ref = {{Pubchemcite|correct|PubChem}}
	| ChemSpiderID = 20074656		| ChemSpiderID = 20074656
	| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}		| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
Line 29:		Line 38:
	| UNII_Ref = {{fdacite|correct|FDA}}		| UNII_Ref = {{fdacite|correct|FDA}}
	| EINECS = 237-875-5		| EINECS = 237-875-5
			| ChEBI_Ref = {{ebicite|correct|EBI}}
	| ChEBI = 30069		| ChEBI = 30069
	| RTECS = V03AB31
	| Gmelin = 1093743		| Gmelin = 1093743
	| SMILES = ....N#C(C#N)(C#N)(C#N)(C#N)C#N.N#C(C#N)(C#N)(C#N)(C#N)C#N.N#C(C#N)(C#N)(C#N)(C#N)C#N		| SMILES = ....N#C(C#N)(C#N)(C#N)(C#N)C#N.N#C(C#N)(C#N)(C#N)(C#N)C#N.N#C(C#N)(C#N)(C#N)(C#N)C#N
	| StdInChI = 1S/18CN.7Fe/c18*1-2;;;;;;;/q;;;;;;;;;;;;;;;;;;3*-4;4*+3		| StdInChI = 1S/18CN.7Fe/c18*1-2;;;;;;;/q;;;;;;;;;;;;;;;;;;3*-4;4*+3
	| StdInChI_Ref = {{stdinchicite|changed|chemspider}}		| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
	| StdInChIKey = DNMNDNSFJMUUFM-UHFFFAOYSA-N		| StdInChIKey = DNMNDNSFJMUUFM-UHFFFAOYSA-N
	| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}		| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
	}}		}}
	| Section2 = {{Chembox Properties		| Section2 = {{Chembox Properties
	| C = 18		| C=18 | Fe=7 | N=18
	| Fe = 7		| Solubility = Insoluble
	| N = 18
	| ExactMass = 859.599927021 g mol<sup>−1</sup>
	| Appearance = Blue opaque crystals}}		| Appearance = Blue opaque crystals}}
	| Section3 = {{Chembox Pharmacology		| Section3 = {{Chembox Structure
			| CrystalStruct = Face-centered cubic, ]
			| SpaceGroup = Fm{{overline|3}}m, No. 225<ref>{{cite book |title=International Tables for Crystallography, Vol. A |isbn=978-0-470-68575-4 |edition=2016 |last1=Fuess |first1=H. |date=20 July 2010 |publisher=Wiley }}</ref> }}
			| Section4 =
			| Section5 =
			| Section6 = {{Chembox Pharmacology
			| ATCCode_prefix = V03
			| ATCCode_suffix = AB31
	| AdminRoutes = Oral}}		| AdminRoutes = Oral}}
	| Section4 = {{Chembox Hazards		| Section7 = {{Chembox Hazards
	| ExternalMSDS = }}		| ExternalSDS = }}
	| Section5 = {{Chembox Related		| Section8 = {{Chembox Related
	| OtherCations = ]<br />		| OtherCations = ]<br />
	]}}		]}}
	}}		}}
	'''Prussian blue''' is a dark blue ] with the idealized ] Fe<sub>7</sub>(CN)<sub>18</sub> Another name for the color ''Prussian blue'' is ''Berlin blue'' or, in ], ''Parisian blue''. '''Turnbull's blue''' is the same substance but is made from different ]s. It is employed as a very fine ], as the compound itself is not soluble in water.		'''Prussian blue''' (also known as '''Berlin blue''', '''Brandenburg blue''', '''Parisian''' and '''Paris blue''') is a dark ] ] produced by oxidation of ferrous ] salts. It has the ] {{chem2|Fe4(3+)])6]3}}. '''Turnbull's blue''' is essentially identical chemically, excepting that it has different impurities and particle sizes—because it is made from different ]s—and thus it has a slightly different color.
	Prussian blue is one of the first synthetic pigments. It is famously complex,<ref name=Dunbar/> owing to the presence of variable amounts of other ions and the sensitive dependence of its appearance on the size of the colloidal particles formed when it is made. The pigment is used in ]s, and it is the traditional "blue" in ]s. It has been used as an ] for certain kinds of ] (] and ]).		Prussian blue was created in the early 18th century and is the first modern ] pigment. It is prepared as a very fine ], because the compound is not soluble in water. It contains variable amounts<ref name=Dunbar/> of other ions and its appearance depends sensitively on the size of the colloidal particles. The pigment is used in ]s, it became prominent in 19th-century {{lang|ja-Latn|]}} ({{lang|ja|藍摺り絵}}) ]s, and it is the traditional "blue" in technical ]s.
			In medicine, orally administered Prussian blue is used as an ] for certain kinds of ], e.g., by ] and radioactive isotopes of ]. The therapy exploits Prussian blue's ion-exchange properties and high affinity for certain "]" metal ]. It is on the ], the most important medications needed in a basic ].<ref>{{cite web |title=WHO Model List of Essential Medicines |url=http://apps.who.int/iris/bitstream/10665/93142/1/EML_18_eng.pdf?ua=1 |work=] |access-date=22 April 2014 |date=October 2013 }}</ref>
	Prussian blue lent its name to ], which was derived from it, and to ] (originally meaning "blue compound of iron", from Latin ''ferrum'' and Greek κυανεος). As ferrocyanide is made of iron and CN ]s, reinterpreting the component "-cyanide" in the compound word produced the word "]" for compounds containing the CN radical.
			Prussian blue lent its name to ] (hydrogen cyanide) derived from it. In German, hydrogen cyanide is called {{lang|de|Blausäure}} ('blue acid'). Cyanide also acquired its name from this relationship.
	==History==		==History==
			]'' by ], an artwork that makes extensive use of Prussian blue|alt=|200x200px|left]]
	Prussian blue was probably synthesized for the first time by the paint maker ] in Berlin around the year 1706.<ref name=Bartoll>{{cite journal| url =http://www.ndt.net/article/art2008/papers/029bartoll.pdf| title =The early use of prussian blue in paintings| format= PDF| author = Jens Bartoll| journal = 9th International Conference on NDT of Art, Jerusalem Israel, 25–30 May 2008| accessdate = 2010-01-22}}</ref> Most historical sources do not mention a first name of Diesbach. Only Berger refers to him as Johann Jacob Diesbach.<ref>J. E. Berger: ''Kerrn aller Fridrichs=Städtschen Begebenheiten'' Manuskript, Berlin, ca.1730 (Berlin, Staatsbibliothek zu Berlin – Preußischer Kulturbesitz, Handschriftenabteilung, Ms. Boruss. quart. 124)</ref> It was named "Preußisch blau" and "Berlinisch Blau" in 1709 by its first trader.<ref name=Frisch>J. L. Frisch: ''Briefwechsel mit Gottfried Wilhelm Leibniz'' L. H. Fischer (ed.), Berlin, Stankiewicz Buchdruck, 1896, reprint Hildesheim/New York: Georg Olms Verlag, 1976</ref> The pigment was an important topic in the letters exchanged between ] and the president of the Royal Academy of Sciences, ], between 1708 and 1716.<ref name=Frisch/> It is first mentioned in a letter written by Frisch to Leibniz, from March 31, 1708. Not later than 1708, Frisch began to promote and sell the pigment across Europe. By August 1709, the pigment had been termed "Preussisch blau"; by November 1709, the German name "Berlinisch Blau" had been used for the first time by Frisch. Frisch himself is the author of the first known publication of Prussian blue in the paper ''Notitia Coerulei Berolinensis nuper inventi'' in 1710, as can be deduced from his letters. Diesbach had been working for Frisch since about 1701.
			Prussian blue pigment is significant since it was the first stable and relatively ] blue pigment to be widely used since the loss of knowledge regarding the synthesis of ]. European painters had previously used a number of pigments such as ], ], and ], and the extremely expensive ] made from ]. ] and ], likewise, did not have access to a long-lasting blue pigment until they began to import Prussian blue from Europe.<ref name="StClair">{{Cite book|title=The Secret Lives of Colour|last=St. Clair|first=Kassia|publisher=John Murray|year=2016|isbn=9781473630819|location=London|pages=189–191|oclc=936144129}}</ref>
			Prussian blue {{chem2|]7(])18}} (also ({{chem2|Fe43*xH2O}}) was probably synthesized for the first time by the paint maker ] in Berlin around 1706.<ref name=Bartoll>{{cite journal| url =http://www.ndt.net/article/art2008/papers/029bartoll.pdf| title =The early use of prussian blue in paintings| author= Bartoll, Jens | journal= 9th International Conference on NDT of Art, Jerusalem Israel, 25–30 May 2008| access-date= 2010-01-22}}</ref><ref>Berger, J. E. (c.1730) ''Kerrn aller Fridrichs=Städtschen Begebenheiten''. Staatsbibliothek zu Berlin – Preußischer Kulturbesitz, Handschriftenabteilung, Ms. Boruss. quart. 124.</ref> The pigment is believed to have been accidentally created when Diesbach used ] tainted with ] to create some red ] dye. The original dye required potash, ], and dried cochineal. Instead, the blood, potash, and iron sulfate reacted to create a compound known as iron ferrocyanide, which, unlike the desired red pigment, has a very distinct blue hue.<ref>{{Cite book|title=The Brilliant History of Color in Art|last=Finlay|first=Victoria|publisher=J. Paul Getty Museum|year=2014|isbn=978-1606064290|pages=86–87}}</ref> It was named {{lang|de|Preußisch blau}} and {{lang|de|Berlinisch Blau}} in 1709 by its first trader.<ref name=Frisch>Frisch, J. L. (1896) ''Briefwechsel mit Gottfried Wilhelm Leibniz'' L. H. Fischer (ed.), Berlin, Stankiewicz Buchdruck, reprint Hildesheim/New York: Georg Olms Verlag, 1976</ref><ref>{{cite journal |last1=Frisch |first1=J. L. |title=Serius Exhibita. Notitia Coerulei Berolinensis nuper inventi |journal=Miscellanea Berolinensia Ad Incrementum Scientiarum |date=1710 |volume=1 |pages=377–378 |url=https://babel.hathitrust.org/cgi/pt?id=mdp.39015039502011&view=1up&seq=459 |trans-title=Addendum. Information about the recently discovered Berlin blue. |language=Latin}}</ref><ref>{{cite journal |last1=Kraft |first1=Alexander |title="Notitia Coerulei Berolinensis nuper inventi" on the 300th anniversary of the first publication on Prussian blue |journal=Bulletin for the History of Chemistry |date=2011 |volume=36 |issue=1 |pages=3–9 |pmid=21612121 |url=http://acshist.scs.illinois.edu/bulletin_open_access/v36-1/v36-1%20p3-9.pdf}}</ref>
	In 1731, ] published an account of the first synthesis of Prussian blue.<ref>G. E. Stahl: ''Experimenta, Observationes, Animadversiones'' CCC Numero, Chymicae et Physicae, (Berlin, 1731), .</ref> The story involves not only Diesbach but also ]. Diesbach was attempting to create a red ] from ] but obtained the blue instead as a result of the contaminated ] he was using. He borrowed the potash from Dippel, who had used it to produce his "animal oil". No other known historical source mentions Dippel in this context. It is therefore difficult to judge the reliability of this story today. In 1724, the recipe was finally published by John Woodward.<ref>{{cite journal|author=Woodward, J. |title=Praeparatio coerulei Prussiaci es Germanica missa ad Johannem Woodward..|journal=Philosophical Transactions of the Royal Society of London |year=1724–1725|volume= 33|issue= 381|pages= 15–17|trans_title=Preparation of Prussian blue sent from Germany to John Woodward...|doi=10.1098/rstl.1724.0005}}</ref><ref>{{cite journal|author=Brown, John |title=Observations and Experiments upon the Foregoing Preparation|jstor=103734|doi=10.1098/rstl.1724.0006|bibcode=1724RSPT...33...17B|journal=Philosophical Transactions|year=1724–1725|volume=33|issue=381|pages=17–24}}. The recipe was subsequently published in Geoffroy, "Observations sur la Preparation de Bleu de Prusse ou Bleu de Berlin," ''Mémoires de l'Académie royale des Sciences année 1725'' (Paris, 1727), pp. 153–172.</ref><ref>Sarah Lowengard, ''The Creation of Color in Eighteenth-Century Europe'' (New York, New York: Columbia University Press, 2008), .</ref>
			The pigment readily replaced the expensive lapis lazuli-derived ultramarine and was an important topic in the letters exchanged between ] and the president of the ], ], between 1708 and 1716.<ref name=Frisch/> It is first mentioned in a letter written by Frisch to Leibniz, from March 31, 1708. Not later than 1708, Frisch began to promote and sell the pigment across Europe. By August 1709, the pigment had been termed {{lang|de|Preussisch blau}}; by November 1709, the German name {{lang|de|Berlinisch Blau}} had been used for the first time by Frisch. Frisch himself is the author of the first known publication of Prussian blue in the paper {{lang|la|Notitia Coerulei Berolinensis nuper inventi}} in 1710, as can be deduced from his letters. Diesbach had been working for Frisch since about 1701.
	To date, the "Entombment of Christ", dated 1709 by ] (Picture Gallery, ], Potsdam) is the oldest known painting where Prussian blue was used. Around 1710, painters at the Prussian court were already using the pigment. At around the same time, Prussian blue arrived in Paris, where ] and later his successors ] and ] used it in their paintings.<ref>J.Bartoll, B. Jackisch, M. Most, E. Wenders de Calisse, C. M. Vogtherr: ''Early Prussian Blue. Blue and green pigments in the paintings by Watteau, Lancret and Pater in the collection of Frederick II of Prussia'' In: ''TECHNE'' 25, 2007, pp. 39–46</ref>
			]
			To date, the ''Entombment of Christ'', dated 1709 by ] (Picture Gallery, ], Potsdam) is the oldest known painting where Prussian blue was used. Around 1710, painters at the ] were already using the pigment. At around the same time, Prussian blue arrived in Paris, where ] and later his successors ] and ] used it in their paintings.<ref name="Bartoll" /><ref>{{cite journal|url=https://philpapers.org/rec/BAREPB|author1=Bartoll, J. |author2=Jackisch, B. |author3=Most, M. |author4=Wenders de Calisse, E. |author5=Vogtherr, C. M. |title=Early Prussian Blue. Blue and green pigments in the paintings by Watteau, Lancret and Pater in the collection of Frederick II of Prussia|journal=Techné |volume= 25|year= 2007|pages=39–46}}</ref> ] used the pigment extensively for both blues and greens.<ref>{{Cite journal|last=Mulherron|first=Jamie|date=2001|title=Prussian Blue, Boucher and Newton: the Material, Practice and Theory of Rococo painting|url=https://www.academia.edu/1806253|journal=Object|number=3|pages=68–93}}</ref>
			In 1731, ] published an account of the first synthesis of Prussian blue.<ref>{{Cite book |last=Stahl |first=Georg Ernst |url=https://books.google.com/books?id=wro5AAAAcAAJ&pg=PA281 |title=Georgii Ernesti Stahlii, Experimenta, Observationes, Animadversiones, CCC Numero, Chymicae Et Physicae: Qualium alibi vel nulla, vel rara, nusquam autem satis ampla, ad debitos nexus, & veros usus, deducta mentio, commemeratio, aut explicatio, invenitur. Qualium partim, in aliis Autoris scriptis, varia mentio facta habetur; partim autem nova commemoratio hoc Tractatu exhibetur: utrimque vero, universa res uberius explicatur atque confirmatur |date=1731 |publisher=Haude |language=la}}</ref> The story involves not only Diesbach, but also ]. Diesbach was attempting to create a red ] from cochineal, but obtained the blue instead as a result of the contaminated potash he was using. He borrowed the potash from Dippel, who had used it to produce his ]. No other known historical source mentions Dippel in this context. It is, therefore, difficult to judge the reliability of this story today. In 1724, the recipe was finally published by John Woodward.<ref>{{cite journal|author=Woodward, J. |title=Praeparatio coerulei Prussiaci es Germanica missa ad Johannem Woodward..|journal=Philosophical Transactions of the Royal Society of London |year=1724–1725|volume= 33|issue= 381|pages= 15–17|trans-title=Preparation of Prussian blue sent from Germany to John Woodward...|doi=10.1098/rstl.1724.0005|doi-access=free}}</ref><ref>{{cite journal|author=Brown, John |title=Observations and Experiments upon the Foregoing Preparation|jstor=103734|doi=10.1098/rstl.1724.0006|bibcode=1724RSPT...33...17B|journal=Philosophical Transactions|year=1724–1725|volume=33|issue=381|pages=17–24|url=https://zenodo.org/record/1432204|doi-access=free}}. The recipe was subsequently published in Geoffroy, Étienne-François (1727) "Observations sur la Preparation de Bleu de Prusse ou Bleu de Berlin," ''Mémoires de l'Académie royale des Sciences année 1725''. Paris. pp. 153–172.</ref><ref>{{Cite web |title=The Creation of Color in Eighteenth-Century Europe: Prussian Blue |url=http://www.gutenberg-e.org/lowengard/C_Chap32.html |access-date=2022-07-28 |website=www.gutenberg-e.org}}</ref>
	]" by ], a famous artwork which makes extensive use of Prussian blue.]]
	This Prussian blue pigment is significant since it was the first stable and relatively lightfast blue pigment to be widely used following the loss of knowledge regarding the synthesis of ]. European painters had previously used a number of pigments such as ], ], and ], which tend to fade, and the extremely expensive ] made from ]. ] and ] likewise did not have access to a long-lasting blue pigment until they began to import Prussian blue from Europe. <!--tangential] has been used extensively by Chinese artists in ] for centuries, and was introduced to Europe in the 18th century.-->
	In 1752 the French chemist ] made the important step of showing the Prussian blue could be reduced to a salt of iron and a new acid, which could be used to reconstitute the dye.<ref>Pierre-Joseph Macquer (1752) ''Mémoires de l'Académie royale des Sciences année 1752'' . . . (Paris, 1756), pp. 60–77. This article was reviewed in ''Histoire de l'Académie royale des Sciences''... (1752), (Paris, 1756), pp. 79–85.</ref> The new acid, ], first isolated from Prussian blue in pure form and characterized about 1783 by the Swedish chemist ], was eventually given the name ''Blausäure'' (literally "Blue acid") because of its derivation from Prussian blue, and in English became known popularly as ''Prussic acid.'' Prussian blue would also give the name to the ] and ] family of compounds. Ferrocyanide (which is yellow) was coined as ] for "iron-containing blue material", since it was first isolated from Prussian blue. Cyanide, a colorless anion that forms in the process of making Prussian Blue, was named, in turn, for hydrogen cyanide (also colorless), and ultimately from ferrocyanide. It is for this reason that ''cyanide,'' even though the name of a colorless radical, is a Latinized form of the Greek word for "dark blue."		In 1752, French chemist ] made the important step of showing Prussian blue could be reduced to a salt of iron and a new acid, which could be used to reconstitute the dye.<ref>Macquer, Pierre-Joseph (1752) ''Mémoires de l'Académie royale des Sciences année 1752'' ... (Paris, 1756), pp. 60–77. This article was reviewed in ''Histoire de l'Académie royale des Sciences''... (1752), (Paris, 1756), pp. 79–85.</ref> The new acid, ], first isolated from Prussian blue in pure form and characterized in 1782 by Swedish chemist ],<ref>Scheele, Carl W. (1782) (Experiment concerning the coloring substance in Berlin blue), ''Kungliga Svenska Vetenskapsakademiens handlingar'' (Royal Swedish Academy of Science's Proceedings), '''3''': 264–275 (in Swedish). Reprinted in Latin as: in: Carl Wilhelm Scheele with Ernst Benjamin Gottlieb Hebenstreit (ed.) and Gottfried Heinrich Schäfer (trans.), ''Opuscula Chemica et Physica'' (Leipzig ("Lipsiae"), (Germany): Johann Godfried Müller, 1789), vol. 2, pages 148–174.</ref> was eventually given the name {{lang|de|Blausäure}} (literally "blue acid") because of its derivation from Prussian blue, and in English became known popularly as Prussic acid. ], a colorless anion that forms in the process of making Prussian blue, derives its name from the Greek word for dark blue.
			In the late 1800s, ] ], the ] ] of ], ] ] with Prussian blue made with ], believing that this was the true ] dye. Even though some have questioned its identity as techeiles because of its artificial production, and claimed that had Rabbi Leiner been aware of this he would have retracted his position that his dye was techeiles,<ref>see ]</ref> others have disputed this and claimed that Rabbi Leiner would not have retracted.<ref>{{cite web |date=8 April 2008 |title=Has the long lost chilazon, source of the biblical blue techeiles dye been rediscovered? |url=http://www.chilazon.com:80/ |url-status=live |archive-url=https://web.archive.org/web/20080408142709/http://www.chilazon.com/ |archive-date=8 April 2008 |access-date=12 May 2020}}</ref>
	==Production==
	Prussian blue is produced by oxidation of ferrous ferrocyanide salts. These white solids have the formula M<sub>2</sub>Fe where M<sup>+</sup> = Na<sup>+</sup> or K<sup>+</sup>. The iron in this material is all ferrous, hence the absence of deep color associated with the mixed valency. Oxidation of this white solid with hydrogen peroxide or sodium chlorate produces ferricyanide and affords Prussian Blue.<ref name=Ullmann/>
			===Military symbol===
	A "soluble" form of PB, K, which is really ]al, can be made from ] and iron(III):
			]
	:K<sup>+</sup> + Fe<sup>3+</sup> + <sup>4-</sup> → KFe<sup>III</sup>
	The similar reaction of ] and iron(II) results in the same colloidal solution, because <sup>3-</sup> is converted into ferrocyanide.
			From the beginning of the 18th century, Prussian blue was the predominant uniform coat color worn by the infantry and artillery regiments of the ].<ref>Haythornthwaite, Philip (1991) ''Frederick the Great's Army – Infantry''. Bloomsbury USA. p. 14. {{ISBN|1855321602}}</ref> As {{lang|de|Dunkelblau}} (dark blue), this shade achieved a symbolic importance and continued to be worn by most German soldiers for ] and off-duty occasions until the outbreak of ], when it was superseded by greenish-gray field gray ({{lang|de|]}}).<ref>Bull, Stephen (2000) ''World War One: German Army''. Brassey's. pp. 8–10. {{ISBN|1-85753-271-6}}</ref>
	"Insoluble" Prussian blue is produced if in the reactions above an excess of Fe<sup>3+</sup> or Fe<sup>2+</sup>, respectively, is added.&nbsp; In the first case:
	:4Fe<sup>3+</sup> + 3<sup>4-</sup> → Fe<sup>III</sup><sub>3</sub>&nbsp;<ref>Egon Wiberg,Nils Wiberg,Arnold Frederick Holleman: , p.1444. Academic Press, 2001; Google books</ref>
			==Synthesis==
	==="Turnbull's blue"===
			Prussian blue is produced by oxidation of ferrous ferrocyanide salts. These white solids have the formula {{chem|M|2|Fe}} where {{chem|M|+}} = {{chem|Na|+}} or {{chem|K|+}}. The iron in this material is all ferrous, hence the absence of deep color associated with the mixed valency. Oxidation of this white solid with hydrogen peroxide or sodium chlorate produces ferricyanide and affords Prussian blue.<ref name=Ullmann/>
	] ion, used to make 'Turnbull's blue'.]]
	In former times, it was thought that addition of Fe(II) salts to a solution of ] affords a material different from Prussian blue. The product was traditionally named "Turnbull's Blue" (TB). It has been shown, however, by means of ] and ] methods, that the structures of PB and TB are identical.<ref>{{cite journal|author=|doi=10.1021/ac00278a041|title=Photoacoustic spectra of prussian blue and photochemical reaction of ferric ferricyanide|year=1984|last1=Ozeki|first1=Toru.|last2=Matsumoto|first2=Koichi.|last3=Hikime|first3=Seiichiro.|journal=Analytical Chemistry|volume=56|issue=14|pages=2819}}</ref><ref>{{cite journal|author=|doi=10.1021/ic50091a012|title=Calorimetric study of Prussian blue and Turnbull's blue formation|year=1970|last1=Izatt|first1=Reed M.|last2=Watt|first2=Gerald D.|last3=Bartholomew|first3=Calvin H.|last4=Christensen|first4=James J.|journal=Inorganic Chemistry|volume=9|issue=9|pages=2019}}</ref> The differences in the colors for TB and PB reflect subtle differences in the method of precipitation, which strongly affects particle size and impurity content.
			A "soluble" form, {{chem2|KFe(3+)}}, which is really ]al, can be made from ] and iron(III):
			: {{chem2|K(+) + Fe(3+) + (4-) -> KFe(3+)}}
			The similar reaction of ] and iron(II) results in the same colloidal solution, because {{chem2|(3-)}} is converted into ferrocyanide.
			The "insoluble" Prussian blue is obtained if, in the reactions above, an excess of Fe(III) is added:
			: {{chem2|4Fe(3+) + 3(4-) -> Fe(3+)3}}&nbsp;<ref>Egon Wiberg, Nils Wiberg, Arnold Frederick Holleman: , p.1444. Academic Press, 2001; Google books</ref>
			Despite the fact that it is prepared from cyanide salts, Prussian blue is not toxic because the cyanide groups are tightly bound to iron.<ref>Journal of Toxicology, </ref> Both ferrocyanide (({{chem2|Fe(2+)(CN)6)(4-)}}) and ferricyanide (({{chem2|Fe(3+)(CN)6)(3-)}}) are particularly stable and non-toxic polymeric ]s due to the strong iron coordination to cyanide ions. Although cyanide bonds well with transition metals in general like chromium, these non-iron coordination compounds are not as stable as iron cyanides, therefore increasing the risk of releasing CN<sup>−</sup> ions, and subsequently comparative toxicity.<ref>{{cite journal | author=Jonathan R. Thurston, Scott E. Waters, Brian H. Robb, Michael P. Marshak |title=Organic and Metal-Organic RFBs |journal=Encyclopedia of Energy Storage |date=March 2022 |volume=2 |pages=423–435 |doi=10.1016/B978-0-12-819723-3.00082-2 |isbn=9780128197301 |s2cid=236672995 |url=https://doi.org/10.1016/B978-0-12-819723-3.00082-2}}</ref>
			===Turnbull's blue===
			] ion, used to make Turnbull's blue|alt=]]
			In former times, the addition of iron(II) salts to a solution of ] was thought to afford a material different from Prussian blue. The product was traditionally named Turnbull's blue (TB). ] and ] methods have shown, though, that the structures of PB and TB are identical.<ref>{{cite journal|doi=10.1021/ac00278a041|title=Photoacoustic spectra of prussian blue and photochemical reaction of ferric ferricyanide|year=1984|last1=Ozeki|first1=Toru.|last2=Matsumoto|first2=Koichi.|last3=Hikime|first3=Seiichiro.|journal=Analytical Chemistry|volume=56|issue=14|pages=2819}}</ref><ref>{{cite journal|doi=10.1021/ic50091a012|title=Calorimetric study of Prussian blue and Turnbull's blue formation|year=1970|last1=Izatt|first1=Reed M.|last2=Watt|first2=Gerald D.|last3=Bartholomew|first3=Calvin H.|last4=Christensen|first4=James J.|journal=Inorganic Chemistry|volume=9|issue=9|pages=2019|author-link1=Reed M. Izatt|url=https://digital.library.unt.edu/ark:/67531/metadc867411/|type=Submitted manuscript}}</ref> The differences in the colors for TB and PB reflect subtle differences in the methods of precipitation, which strongly affect particle size and impurity content.
			===Prussian white===
			<!-- As no dedicated page already exists, some preliminary information on the Prussian white is provided here, awaiting to be incorporated in a self-supporting page when there will be sufficient materials gathered to make it. In the meantime, four redirect pages (Prussian white, Berlin white, Everett's salt, and Everitt's salt) already point here to inform the Misplaced Pages reader. Please, do not remove this section {{Main article|Prussian white}} -->
			Prussian white, also known as ''Berlin white'' or ''Everett's salt'', is the ] ] of the totally ] form of the Prussian blue in which all iron is present as Fe(II). It is a sodium ] of Fe(II) of formula {{Chem2|Na2Fe}}.<ref name="MacsenLabs2023">{{cite web | title=Prussian White | website=Macsen Labs | date=2023-10-28 | url=https://www.macsenlab.com/battery-cathode-materials/prussian-white/ | access-date=2024-03-16}}</ref> Its ] value is {{Nowrap|314 g/mol}}.<ref name="MacsenLabs2023" />
			A more generic formula allowing for the substitution of {{Chem2|Na+}} cations by {{Chem2|K+}} cations is {{Chem2|A_{(2-x)}B_{x}Fe2(CN)6}} (in which A or B = {{Chem2|Na+}} or {{Chem2|K+}}).
			The Prussian white is closely related to the Prussian blue, but it significantly differs by its crystallographic structure, molecular framework pore size, and its color. The cubic sodium Prussian white, {{Chem2|Na_{(2-x)}K_{x}Fe2(CN)6·yH2O}}, and potassium Prussian white, {{Chem2|K_{(2-x)}Na_{x}Fe2(CN)6·yH2O}}, are candidates as ] materials for ].<ref name="Piernas-Muñoz2016">{{cite journal | last1=Piernas-Muñoz | first1=María José | last2=Castillo-Martínez | first2=Elizabeth | last3=Bondarchuk | first3=Oleksandr | last4=Armand | first4=Michel | last5=Rojo | first5=Teófilo | year=2016 | title=Higher voltage plateau cubic Prussian white for Na-ion batteries | journal=Journal of Power Sources | publisher=Elsevier | volume=324 | pages=766–773 | issn=0378-7753 | doi=10.1016/j.jpowsour.2016.05.050| bibcode=2016JPS...324..766P }}</ref> The insertion of {{Chem2|Na+}} and {{Chem2|K+}} cations in the framework of potassium Prussian white provides favorable synergistic effects improving the long-term battery stability and increasing the number of possible recharge cycles, lengthening its service life.<ref name="Piernas-Muñoz2016" /> The large-size framework of Prussian white easily accommodating {{Chem2|Na+}} and {{Chem2|K+}} cations facilitates their intercalation and subsequent extraction during the charge/discharge cycles. The spacious and rigid host crystal structure contributes to its volumetric stability against the internal swelling ] and ] developing in sodium-batteries after many cycles.<ref name="MacsenLabs2023" /> The material also offers perspectives of high ] (Ah/kg) while providing high recharge rate, even at low temperature.<ref name="MacsenLabs2023" />
	==Properties==		==Properties==
	Prussian blue is a ] blue powder. It is insoluble, but the ]s tend to form a ]. Such colloids can pass through fine filters.<ref name=Dunbar>{{cite journal|author=Dunbar, K. R. and Heintz, R. A.|title=Chemistry of Transition Metal Cyanide Compounds: Modern Perspectives|journal=Progress in Inorganic Chemistry|year= 1997|volume= 45|pages=283–391}}</ref> Despite being one of the oldest known synthetic compounds, the composition of Prussian blue remained uncertain for many years. The precise identification of Prussian blue was complicated by three factors:		Prussian blue is a ] blue powder. It is insoluble, but the ]s tend to form a colloid. Such colloids can pass through fine filters.<ref name=Dunbar>{{Cite book|author1=Dunbar, K. R. |author2=Heintz, R. A. |name-list-style=amp |title=Chemistry of Transition Metal Cyanide Compounds: Modern Perspectives|year= 1997|volume= 45|pages=283–391|doi=10.1002/9780470166468.ch4|series=Progress in Inorganic Chemistry|isbn=9780470166468}}</ref> Despite being one of the oldest known synthetic compounds, the composition of Prussian blue remained uncertain for many years. Its precise identification was complicated by three factors:
	# Prussian blue is extremely insoluble but also tends to form colloids;		* Prussian blue is extremely insoluble, but also tends to form colloids
	# Traditional syntheses tend to afford impure compositions;		* Traditional syntheses tend to afford impure compositions
	# Even pure Prussian blue is structurally complex, defying routine crystallographic analysis.		* Even pure Prussian blue is structurally complex, defying routine crystallographic analysis
	===Crystal structure===		===Crystal structure===
			]s in idealized Prussian blue]]
	The ] of insoluble Prussian blue is Fe<sub>7</sub>(CN)<sub>18</sub>·xH<sub>2</sub>O, where x = 14–16. The structure was determined by using ], ], ], and ]. Since ] cannot distinguish carbon from nitrogen, the location of these lighter elements is deduced by spectroscopic means as well as by observing the distances from the iron atom centers.
			] of Prussian blue, with all sites occupied. Actually, one fourth of the {{chem2|Fe(CN)6}} groups shown will be missing, at random, giving on average only 18 cyanide ions (rather than the 24 shown) and three ferrous iron atoms.]]
			] profile for Prussian blue crystal, ] annotated. Image generated using CrystalMaker software.]]
			The ] of insoluble Prussian blue is {{chem2|Fe7(CN)18*''x''H2O}}, where ''x''&nbsp;=&nbsp;14–16. The structure was determined by using ], ], ], and ]. Since X-ray diffraction cannot easily distinguish carbon from nitrogen in the presence of heavier elements such as iron, the location of these lighter elements is deduced by spectroscopic means, as well as by observing the distances from the iron atom centers. ] can easily distinguish N and C atoms, and it has been used to determine the detailed structure of Prussian blue and its analogs.<ref>Electrochemistry of polynuclear transition-metal cyanides – Prussian blue and its analogs. 1986. Accounts of Chemical Research. 19/162-168. {{doi|10.1021/ar00126a001}}.</ref><ref>Low Defect FeFe(CN)<sub>6</sub> Framework as Stable Host Material for High Performance Li-Ion Batteries. 2016. ACS Applied Materials and Interfaces. 8/23706-23712. {{doi|10.1021/acsami.6b06880}}.</ref><ref>Prussian blue analogues and their derived materials for electrochemical energy storage: Promises and Challenges. 2024. Materials Research Bulletin. 170/ {{doi|10.1016/j.materresbull.2023.112593}}.</ref><ref>Some performance characteristics of a Prussian blue battery. 1985. Journal of the Electrochemical Society. 132/1382-1384. {{doi|10.1149/1.2114121}}.</ref><ref>A neutron diffraction study of Prussian blue, Fe<sub>4</sub><sub>3</sub>. 14D<sub>2</sub>O. 1974. Zeitschrift fur Physikalische Chemie. 92/354-357. {{doi|10.1524/zpch.1974.92.4-6.354}}.</ref><ref>Valence Delocalization in Prussian Blue Fe(III)<sub>4</sub><sub>3</sub>·xD<sub>2</sub>O, by Polarized Neutron Diffraction. 1980. Helvetica Chimica Acta. 63/148-153. {{doi|10.1002/hlca.19800630115}}.</ref><ref>Neutron Diffraction Study of Prussian Blue, Fe<sub>4</sub><sub>3</sub>·xH<sub>2</sub>O. Location of Water Molecules and Long-Range Magnetic Order. 1980. Inorganic Chemistry. 19/956-959. {{doi|10.1021/ic50206a032}}.</ref><ref>Neutron and X-ray diffraction studies on powders and single crystals of compounds structurally related to Prussian blue. 1999. Zeitschrift fur Naturforschung – Section B Journal of Chemical Sciences. 54/870-876. {{doi|10.1515/znb-1999-0708}}.</ref><ref>Crystalline, mixed-valence manganese analogue of Prussian blue: Magnetic, spectroscopic, X-ray and neutron diffraction studies. 2004. Journal of the American Chemical Society. 126/16472-16477. {{doi|10.1021/ja0465451}}.</ref><ref>Neutron diffraction and neutron vibrational spectroscopy studies of hydrogen adsorption in the Prussian blue analogue Cu<sub>3</sub><sub>2</sub>. 2006. Chemistry of Materials. 18/3221-3224. {{doi|10.1021/cm0608600}}.</ref><ref>Neutron diffraction study of molecular magnetic compound Ni<sub>1.125</sub>Co<sub>0.375</sub>·6.4H<sub>2</sub>O. 2006. Physica B: Condensed Matter. 385-386 I/444-446. {{doi|10.1016/j.physb.2006.05.147}}.</ref>
			PB has a ] lattice structure, with four iron(III) ions per unit cell. "Soluble" PB crystals contain interstitial {{chem2|K(+)}} ions; insoluble PB has interstitial water, instead. In ideal insoluble PB crystals, the cubic framework is built from Fe(II)–C–N–Fe(III) sequences, with Fe(II)–carbon distances of 1.92 ] and Fe(III)–nitrogen distances of 2.03 Å. One-fourth of the sites of {{chem2|Fe(CN)6}} subunits (supposedly at random) are vacant (empty), leaving three such groups on average per unit cell.<ref name='Herren'/> The empty nitrogen sites are filled with water molecules instead, which are coordinated to Fe(III).
			] of Prussian blue determined by ],<ref name='Herren' /> with ] water molecules both in cyanide ion positions and in the void space of the framework. Again, one fourth of the {{chem2|Fe(CN)6}} groups shown will be missing. This illustration superimposes both possibilities at each site — water molecules or cyanide ions.]]
	PB has a ]. Soluble PB crystals contain interstitial K<sup>+</sup> ions; insoluble PB has interstitial water instead.<br />
	In ideal insoluble PB crystals, the cubic framework is built from Fe(II)-C-N-Fe(III) sequences, with Fe(II)-carbon distances of 1.92 Å and Fe(III)-nitrogen distances of 2.03 Å. One-fourth of the sites of Fe(CN)<sub>6</sub> subunits are vacant (empty), leaving three such groups. The empty nitrogen sites are filled with water molecules instead, which are coordinated to Fe(III).
	The Fe(II) centers, which are ], are surrounded by six carbon ]s in an ] configuration. The Fe(III) centers, which are ], are octahedrally surrounded on average by 4.5 nitrogen atoms and 1.5 oxygen atoms (the oxygen from the six coordinated water molecules). Additional eight (interstitial) water molecules are present in the unit cell, either as isolated molecules or ]ed to the coordinated water.		The Fe(II) centers, which are ], are surrounded by six carbon ]s in an ] configuration. The Fe(III) centers, which are ], are octahedrally surrounded on average by 4.5 nitrogen atoms and 1.5 oxygen atoms (the oxygen from the six coordinated water molecules). Around eight (interstitial) water molecules are present in the unit cell, either as isolated molecules or ]ed to the coordinated water. It is worth noting that in soluble ]s Fe(II or III) is always coordinated to the carbon atom of a ], whereas in crystalline Prussian blue Fe ions are coordinated to both C and N.<ref>Prussian blue analogues and their derived materials for electrochemical energy storage: Promises and Challenges. 2024. Materials Research Bulletin. 170/. M. Fayaz, W. Lai, J. Li, W. Chen, X. Luo, Z. Wang, et al. {{doi|10.1016/j.materresbull.2023.112593}}</ref>
	The composition is notoriously variable due to the presence of lattice defects, allowing it to be hydrated to various degrees as water molecules are incorporated into the structure to occupy ] vacancies. The variability of Prussian blue's composition is attributable to its low ], which leads to its rapid ] without the time to achieve full equilibrium between solid and liquid.<ref name='Herren'>{{cite journal|author=|doi=10.1021/ic50206a032|title=Neutron diffraction study of Prussian Blue, Fe4&#91;Fe(CN)6&#93;3.xH2O. Location of water molecules and long-range magnetic order|year=1980|last1=Herren|first1=F.|last2=Fischer|first2=P.|last3=Ludi|first3=A.|last4=Haelg|first4=W.|journal=Inorganic Chemistry|volume=19|issue=4|pages=956}}</ref>		The composition is notoriously variable due to the presence of lattice defects, allowing it to be hydrated to various degrees as water molecules are incorporated into the structure to occupy ] vacancies. The variability of Prussian blue's composition is attributable to its low ], which leads to its rapid ] without the time to achieve full equilibrium between solid and liquid.<ref name='Herren'>{{cite journal|doi=10.1021/ic50206a032|title=Neutron diffraction study of Prussian blue, Fe<sub>4</sub>&#91;Fe(CN)<sub>6</sub>&#93;<sub>3</sub>·xH<sub>2</sub>O. Location of water molecules and long-range magnetic order|year=1980|last1=Herren|first1=F.|last2=Fischer|first2=P.|last3=Ludi|first3=A.|last4=Haelg|first4=W.|journal=Inorganic Chemistry|volume=19|issue=4|pages=956}}</ref><ref name='Lundgren'>{{cite journal|doi=10.1021/ic00278a036 |title=Observations on the composition of Prussian blue films and their electrochemistry|year=1988|last1=Lundgren|first1=C. A.|last2=Murray|first2=Royce W.|journal=Inorganic Chemistry|volume=27|issue=5|pages=933}}</ref>
	<ref name='Lundgren'>{{cite journal|author=|doi=10.1021/ic00278a036 |title=Observations on the composition of Prussian blue films and their electrochemistry|year=1988|last1=Lundgren|first1=C. A.|last2=Murray|first2=Royce W.|journal=Inorganic Chemistry|volume=27|issue=5|pages=933}}</ref>
	===Color===		===Color===
	Prussian blue is strongly colored and tends towards black and dark purple{{fact|date=October 2011}} when mixed into ]s. The exact hue depends on the method of preparation, which dictates the particle size. The intense blue color of Prussian blue is associated with the energy of the transfer of ]s from Fe(II) to Fe(III). Many such ]s absorb certain wavelengths of visible light resulting from ]. In this case, orange-red light around 680 ]s in wavelength is absorbed, and the transmitted light appears blue as a result.		Prussian blue is strongly colored and tends towards black and dark blue when mixed into ]s. The exact hue depends on the method of preparation, which dictates the particle size. The intense blue color of Prussian blue is associated with the energy of the transfer of ]s from Fe(II) to Fe(III). Many such ]s absorb certain wavelengths of visible light resulting from ]. In this case, orange-red light around 680 ]s in wavelength is absorbed, and the reflected light appears blue as a result.
	PB is ]—changing from blue to colorless upon ]. This change is caused by reduction of the Fe(III) to Fe(II) eliminating the ] that causes Prussian blue's color.		Like most high-] ]s, Prussian blue cannot be accurately displayed on a computer display. Prussian blue is ]—changing from blue to colorless upon ]. This change is caused by reduction of the Fe(III) to Fe(II), eliminating the ] that causes Prussian blue's color.
	==Uses==		==Use==
			===Pigment===
	Because it is easily made, cheap, non-toxic, and intensely colored, Prussian blue has attracted many applications. The dominant uses are for pigments: approximately 12,000 ]s of Prussian blue are produced annually for use in black and bluish ]s. A variety of other pigments also contain the material.<ref name=Ullmann>Völz, Hans G. ''et al.'' "Pigments, Inorganic" in Ullmann's Encyclopedia of Industrial Chemistry, 2006 Wiley-VCH, Weinheim. {{DOI|10.1002/14356007.a20_243.pub2}}.</ref> ] and the pigment formed on ]s—giving them their common name ]s. Certain ]s were once colored with Prussian blue (later relabeled ]). It is also a popular pigment in paints. Similarly, Prussian blue is the basis for ].
			], restored to their original 1859 color scheme of Prussian blue and gold<ref>{{cite web|url=https://www.parliament.uk/about/living-heritage/building/palace/big-ben/elizabeth-tower-and-big-ben-conservation-works-2017-/turning-big-bens-clock-dials-blue/| title=Turning Big Ben's clock dials blue| publisher=UK Parliament| access-date=21 October 2023}}</ref>]]
			Because it is easily made, cheap, nontoxic, and intensely colored, Prussian blue has attracted many applications. It was adopted as a pigment very soon after its invention and was almost immediately widely used in oil paints, watercolor, and dyeing.<ref>Berrie, Barbara H. (1997). "Prussian Blue". In ''Artists' Pigments. A Handbook of their History and Characteristics'', E. W. FitzHugh (ed.). Washington, DC: National Gallery of Art. {{ISBN|0894682563}}.</ref> The dominant uses are for pigments: about 12,000 ]s of Prussian blue are produced annually for use in black and bluish ]s. A variety of other pigments also contain the material.<ref name=Ullmann>Völz, Hans G. ''et al.'' (2006) "Pigments, Inorganic" in Ullmann's Encyclopedia of Industrial Chemistry. Wiley-VCH, Weinheim. {{doi|10.1002/14356007.a20_243.pub2}}.</ref> ] and the pigment formed on ]s—giving them their common name ]s. Certain ]s were once colored with Prussian blue (later relabeled ]). Similarly, Prussian blue is the basis for ].
			Nanoparticles of Prussian blue are used as pigments in some cosmetics ingredients, according to the European Union Observatory for Nanomaterials.
	===Niche uses===
	====Medicine====
	Prussian blue's ability to incorporate monocations makes it useful as a sequestering agent for certain heavy metal poisons. Pharmaceutical-grade Prussian blue in particular is used for patients who have ingested ] or ] ]. According to the ], an adult male can eat at least 10&nbsp;grams of Prussian blue per day without serious harm. The ] (FDA) has determined that the "500 mg Prussian blue capsules, when manufactured under the conditions of an approved New Drug Application (NDA), can be found safe and effective therapy" in certain poisoning cases.<ref>{{cite web| url =http://www.fda.gov/Drugs/EmergencyPreparedness/BioterrorismandDrugPreparedness/ucm130337.htm| title = Questions and Answers on Prussian Blue| accessdate = 2009-06-06}}</ref> Radiogardase (Prussian blue in soluble capsules <ref>Radiogardase: </ref>) is a commercial product for the removal of ] from the intestine and so indirectly from the bloodstream by intervening in the enterohepatic circulation of ],<ref></ref> reducing the internal residency time (and exposure) by about two-thirds.
			{{infobox color
	====Laboratory histopathology stain for iron====
			|title=Prussian blue
	]
			|hex=003153
	Prussian blue is a common ] stain used by ]s to detect the presence of iron in biopsy specimens, such as in bone marrow samples. The original stain formula, known historically (1867) as "]" after its inventor, German pathologist Max Perls (1843–1881), used separate solutions of potassium ferrocyanide and acid to stain tissue (these are now used combined, just before staining). Iron deposits in tissue then form the purple Prussian blue dye in place, and are visualized as blue or purple deposits.<ref>. Accessed April 2, 2009.</ref> The formula is also known as Perls Prussian blue and (incorrectly) as '''Perl's''' Prussian blue.
			|source=]<ref></ref>
			|cmyk=1
			}}
			===Medicine===
			{{Main|Prussian blue (medical use)}}
			Prussian blue's ability to incorporate ] metallic ]s ({{chem2|Me(+)}}) makes it useful as a ] for certain ]s. Pharmaceutical-grade Prussian blue in particular is used for people who have ingested ] ({{chem2|Tl(+)}}) or ] ] ({{chem2|^{134}Cs(+), ^{137}Cs(+)}}). According to the ] (IAEA), an adult male can eat at least 10&nbsp;g of Prussian blue per day without serious harm. The ] (FDA) has determined the "500-mg Prussian blue capsules, when manufactured under the conditions of an approved New Drug Application, can be found safe and effective therapy" in certain poisoning cases.<ref>{{cite web| url =https://www.fda.gov/Drugs/EmergencyPreparedness/BioterrorismandDrugPreparedness/ucm130337.htm| title= Questions and Answers on Prussian Blue| website= ]| archive-url= https://web.archive.org/web/20090710041011/https://www.fda.gov/Drugs/EmergencyPreparedness/BioterrorismandDrugPreparedness/ucm130337.htm| access-date= 2020-03-20| archive-date= 2009-07-10}}</ref><ref>{{cite web |title=Questions and Answers on Calcium-DTPA and Zinc-DTPA (Updated) |url=https://www.fda.gov/drugs/bioterrorism-and-drug-preparedness/questions-and-answers-calcium-dtpa-and-zinc-dtpa-updated |website=U.S. Food & Drug Administration |date=3 November 2018 |access-date=21 March 2020}}</ref> Radiogardase (Prussian blue insoluble capsules <ref>Radiogardase: {{webarchive|url=https://web.archive.org/web/20110320030420/http://www.heyltex.com/radiogardasePackageInsert.php |date=2011-03-20 }}</ref>) is a commercial product for the removal of ] from the ], so indirectly from the ] by intervening in the ] of caesium-137,<ref> {{webarchive|url=https://web.archive.org/web/20071112025717/http://www.heyltex.com/toxicology.php |date=2007-11-12 }}</ref> reducing the internal residency time (and exposure) by about two-thirds. In particular, it was used to ] and remove {{chem2|^{137}Cs(+)}} from those poisoned in the ] in Brazil.<ref name=Dunbar/>
			===Stain for iron===
			Prussian blue is a common ] stain used by ]s to detect the presence of iron in ] specimens, such as in ] samples. The original stain formula, known historically (1867) as "]" after its inventor, German pathologist ] (1843–1881), used separate solutions of ] and acid to stain ] (these are now used combined, just before staining). Iron deposits in tissue then form the purple Prussian blue dye in place, and are visualized as blue or purple deposits.<ref>. Accessed April 2, 2009.</ref>
			<gallery mode="packed" heights="150">
			File:Kupffer cell with hemosiderin and hepatocyte with lipofuscin.jpg|] of the liver, showing a ]s with significant ] deposition next to a hepatocyte with ] pigment. H&E stain.
			File:Kupffer cell with hemosiderin and hepatocyte with lipofuscin, iron stain.jpg|Prussian blue staining, highlighting the hemosiderin pigment as blue.
			File:Intra-alveolar hemosiderin deposition - Prussian blue stain.jpg|Prussian blue stain
			</gallery>
			===By machinists and toolmakers===
			], Prussian blue in an oily base, is the traditional material used for spotting metal surfaces such as ]s and ]s for ]. A thin layer of nondrying paste is applied to a reference surface and transfers to the high spots of the workpiece. The toolmaker then scrapes, stones, or otherwise removes the marked high spots. Prussian blue is preferable because it will not abrade the extremely precise reference surfaces as many ground pigments may. Other uses include marking gear teeth during assembly to determine their interface characteristics.
			=== In analytical chemistry ===
			Prussian blue is formed in the Prussian blue assay for total ]s. Samples and phenolic standards are given acidic ferric chloride and ferricyanide, which is reduced to ferrocyanide by the phenols. The ferric chloride and ferrocyanide react to form Prussian blue. Comparing the absorbance at 700&nbsp;nm of the samples to the standards allows for the determination of total phenols or ]s.<ref name="Hagerman2011">{{cite web |last=Hagerman |first=Ann E. |date=18 March 2011 |title=Tannin Chemistry |url= http://www.users.muohio.edu/hagermae/tannin.pdf |access-date=2009-12-19 |archive-url=https://web.archive.org/web/20130826003253/http://www.users.muohio.edu/hagermae/tannin.pdf |archive-date=2013-08-26 |url-status=dead }}&nbsp;(1.41&nbsp;MB)</ref><ref name="Graham1992">{{cite journal | last=Graham | first=Horace D. | date=1992 | title=Stabilization of the Prussian blue color in the determination of polyphenols | journal=Journal of Agricultural and Food Chemistry | volume=40 | issue=5 | pages=801–805 | issn=0021-8561 | doi=10.1021/jf00017a018}}</ref>
	====By machinists and toolmakers====		=== Household use ===
			Prussian blue is present in some preparations of ], such as ].<ref name="Schwarcz Gazette 20164">{{cite web|url=https://montrealgazette.com/opinion/columnists/the-right-chemistry-columbo-your-laundry-and-liquid-bluing|title=The Right Chemistry: Columbo, your laundry and liquid bluing|author=Schwarcz, Joe|date=January 22, 2016|website=]|access-date=February 28, 2017}}</ref>
	Prussian blue in oil paint is the traditional material used for spotting metal surfaces such as surface plates and bearings for hand scraping. A thin layer of non-drying paste is applied to a reference surface and transfers to the high spots of the workpiece. The toolmaker then scrapes, stones, or otherwise removes the marked high spots. Prussian blue is preferable because it will not abrade the extremely precise reference surfaces as many ground pigments may.
			==Research==
	====Analytical chemistry====
			=== Battery materials ===
	Prussian blue is formed in the Prussian blue assay for total phenols. Samples and phenolic standards are given acidic ferric chloride and ferricyanide which is reduced to ferrocyanide by the phenols. The ferric chloride and ferrocyanide react to form Prussian blue. Comparing the absorbance at 700&nbsp;nm of the samples to the standards allows for the determination of total phenols.<ref>{{PDFlink||1.41&nbsp;MB}}Accessed December 19, 2009</ref>
			] of Prussian Blue ] in solution of different ] ].]]
			Prussian blue (PB) has been studied for its applications in electrochemical energy storage since 1978.<ref name="Neff1978">{{Cite journal|last=Neff|first=Vernon D.|date=1978-06-01|title=Electrochemical oxidation and reduction of thin films of Prussian blue|url=https://iopscience.iop.org/article/10.1149/1.2131575/meta|journal=Journal of the Electrochemical Society|language=en|volume=125|issue=6|pages=886–887|doi=10.1149/1.2131575|bibcode=1978JElS..125..886N|issn=1945-7111}}</ref> Prussian Blue proper (the Fe-Fe solid) shows two well-defined reversible redox transitions in K<sup>+</sup> solutions. Weakly solvated potassium ions (as well as Rb<sup>+</sup> and Cs<sup>+</sup>, not shown) have the ], which fits the framework of Prussian Blue. On the other hand, the sizes of solvated Na<sup>+</sup> and Li<sup>+</sup> are too large for the PB cavity, and the intercalation of these ions is hindered and much slower. The low and high voltage sets of peaks in the cyclic voltammetry correspond to 1 and ⅔ electron per Fe atom, respectively.<ref name="Neff1985">{{cite journal | last=Neff | first=Vernon D. | date=1985-06-01 | title=Some performance characteristics of a Prussian blue battery | journal=Journal of the Electrochemical Society | volume=132 | issue=6 | pages=1382–1384 | issn=0013-4651 | doi=10.1149/1.2114121| bibcode=1985JElS..132.1382N }}</ref> The high voltage set is due to the {{Chem2|Fe(3+)/Fe(2+)}} transition at the low-spin Fe ions coordinated to C-atoms. The low-voltage set is due to high-spin Fe ion coordinated to N-atoms.<ref name="Itaya1986">{{cite journal | last1=Itaya | first1=Kingo | last2=Uchida | first2=Isamu | last3=Neff | first3=Vernon D. | date=1986-06-01 | title=Electrochemistry of polynuclear transition metal cyanides: Prussian blue and its analogues | journal=Accounts of Chemical Research | volume=19 | issue=6 | issn=0001-4842 | doi=10.1021/ar00126a001 | pages=162–168}}</ref><ref name="Wu2016">{{cite journal | last1=Wu | first1=Xianyong | last2=Shao | first2=Miaomiao | last3=Wu | first3=Chenghao | last4=Qian | first4=Jiangfeng | last5=Cao | first5=Yuliang | last6=Ai | first6=Xinping | last7=Yang | first7=Hanxi | date=2016-09-14 | title=Low defect FeFe(CN)<sub>6</sub> framework as stable host material for high performance Li-ion batteries | journal=ACS Applied Materials and Interfaces | volume=8 | issue=36 | pages=23706–23712 | issn=1944-8244 | doi=10.1021/acsami.6b06880| pmid=27556906 }}</ref><ref name="Fayaz2024">{{cite journal | last1=Fayaz | first1=Muhammad | last2=Lai | first2=Wende | last3=Li | first3=Jie | last4=Chen | first4=Wen | last5=Luo | first5=Xianyou | last6=Wang | first6=Zhen | last7=Chen | first7=Yingyu | last8=Li | first8=De | last9=Abbas | first9=Syed Mustansar | last10=Chen | first10=Yong | year=2024 | title=Prussian blue analogues and their derived materials for electrochemical energy storage: Promises and challenges | journal=Materials Research Bulletin | publisher=Elsevier | volume=170 | page=112593 | issn=0025-5408 | doi=10.1016/j.materresbull.2023.112593}}</ref>
			It is possible to replace the Fe metal centers in PB with other metal ions such as Mn, Co, Ni, Zn, ''etc.'' to form electrochemically active Prussian blue analogues (PBAs). PB/PBAs and their derivatives have also been evaluated as electrode materials for reversible alkali-ion insertion and extraction in ], ], and ].
	==Safety==
	Despite the fact that it is prepared from ] salts, Prussian blue is nontoxic because the cyanide groups are tightly bound to Fe. Other polymeric cyanometalates are similarly stable with low toxicity.
	==See also==		==See also==
			* {{annotated link|Blue billy}}
	{{colbegin|3}}
	*]		* ]
			* {{annotated link|Cobalt blue}}
	*]
			* {{annotated link|Crystal violet}}
	*]
			* {{annotated link|Fluorescein}}
	*]
			* {{annotated link|Han purple and Han blue}}
	*]
			* {{annotated link|List of inorganic pigments}}
	*]
			* {{annotated link|Midnight blue}}
	{{colend}}
			* {{annotated link|Phthalocyanine Blue BN}}
	==References==		==References==
	{{Reflist|2}}		{{reflist}}
	==External links==		==External links==
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	*		* {{Webarchive|url=https://web.archive.org/web/20200221153509/http://www.heyltex.com/ |date=2020-02-21 }}
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			* , ColourLex
			* {{cite journal|url = http://www.scs.illinois.edu/~mainzv/HIST/bulletin_open_access/v33-2/v33-2%20p61-67.pdf|first = Alexander|last = Kraft|title = On the discovery and history of Prussian blue|journal = ]|volume = 33|issue = 2|year = 2008|pages = 61–67}}
	{{Shades of blue}}		{{Shades of blue}}
			{{Color topics}}
	{{Antidotes}}		{{Antidotes}}
	{{Stains}}		{{Stains}}
			{{Authority control}}
			{{portal bar|Medicine}}
	{{DEFAULTSORT:Prussian Blue}}		{{DEFAULTSORT:Prussian Blue}}
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