Editing Prussian blue (section)

==Synthesis==
Prussian blue is produced by oxidation of ferrous ferrocyanide salts. These white solids have the formula {{chem|M|2|Fe[Fe(CN)|6|]}} 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/>

A "soluble" form, {{chem2|KFe(3+)[Fe(2+)(CN)6]}}, which is really [[colloid]]al, can be made from [[potassium ferrocyanide]] and iron(III):
: {{chem2|K(+) + Fe(3+) + [Fe(2+)(CN)6](4-) -> KFe(3+)[Fe(2+)(CN)6]}}
The similar reaction of [[potassium ferricyanide]] and iron(II) results in the same colloidal solution, because {{chem2|[Fe(3+)(CN)6](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[Fe(2+)(CN)6](4-) -> Fe(3+)[Fe(3+)Fe(2+)(CN)6]3}}&nbsp;<ref>Egon Wiberg, Nils Wiberg, Arnold Frederick Holleman: [https://books.google.com/books?id=vEwj1WZKThEC&pg=PA1444 Inorganic chemistry], 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, [https://www.tandfonline.com/doi/pdf/10.3109/15563659609013821 Suicide Attempt by Ingestion of Potassium Ferricyanide]</ref> Both ferrocyanide (({{chem2|Fe(2+)(CN)6)(4-)}}) and ferricyanide (({{chem2|Fe(3+)(CN)6)(3-)}}) are particularly stable and non-toxic polymeric [[cyanometalate]]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===
[[File:HexacyanidoferratIII 2.svg|thumb|200x200px|[[Ferricyanide]] ion, used to make Turnbull's blue|alt=]]
In former times, the addition of iron(II) salts to a solution of [[ferricyanide]] was thought to afford a material different from Prussian blue. The product was traditionally named Turnbull's blue (TB). [[X-ray diffraction]] and [[electron diffraction]] 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 Wikipedia reader. Please, do not remove this section {{Main article|Prussian white}} -->

Prussian white, also known as ''Berlin white'' or ''Everett's salt'', is the [[sodium]] [[end-member]] of the totally [[Redox|reduced]] form of the Prussian blue in which all iron is present as Fe(II). It is a sodium [[hexacyanoferrate]] of Fe(II) of formula {{Chem2|Na2Fe[Fe(CN)6]}}.<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 [[molecular weight]] 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 [[cathode]] materials for [[Sodium-ion battery|Na-ion batteries]].<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 [[Stress (mechanics)|stress]] and [[Strain (mechanics)|strain]] developing in sodium-batteries after many cycles.<ref name="MacsenLabs2023" /> The material also offers perspectives of high [[Energy density|energy densities]] (Ah/kg) while providing high recharge rate, even at low temperature.<ref name="MacsenLabs2023" />