Soluble Prussian blue

In the literature the term soluble Prussian blue introduced by Keggin and Miles [5] to determine the KFeFe(CN)6 compound is still widely used. However, it is important to note, that the term soluble refers to the ease with which the potassium ion can be peptized rather than to the real solubility of Prussian blue. Indeed, it can be easily shown by means of cyclic voltammetry that the stability of Prussian blue films on electrode supports is nearly independent of their saturation by potassium cations. Moreover, Itaya and coworkers [9] have not found any appreciable amount of potassium ions in Prussian blue, which makes doubtful structures like KFeFe(CN)6. Thus, the above equation fully describes the Prussian blue/Prussian white redox reaction. 

For cases in which the NPs are not soluble in the supporting electrolyte in which they will be examined, it is possible to solvent-cast a thin film of the NPs on the electrode surface followed by evaporation [44] or to directly apply an insoluble gel containing the NPs [45]. In a related approach, films of anionic Prussian Blue NPs that had been synthesized in a solution containing chitosan (a cationic glucosamine polymer) were drop-cast onto glassy carbon surfaces, giving very stable... 

Solubility data (pA sp) for two dozen hexacyanoferrate(II) and hexacyanoferrate(III) salts, and Pourbaix (pe/pH) diagrams for iron-cyanide-water, iron-sulfide-cyanide-(hydr)oxide, iron-arsenate-cyanide-(hydr)oxide, and iron-copper-cyanide-sulfide-(hydr)oxide, are given in a review ostensibly dedicated to hydrometallurgical extraction of gold and silver. " The electrochemistry of Prussian Blue and related complexes, in the form of thin films on electrodes, has been reviewed. ... 

Such cyanide complexes are also known for several other metals. All the fer-rocyanide complexes may be considered as the salts of ferrocyanic acid H4Fe(CN)e and ferricyanide complexes are that of ferricyanic acid, H3Fe(CN)e. The iron-cyanide complexes of alkali and alkaline-earth metals are water soluble. These metals form yellow and ruby-red salts with ferro-cyanide and ferricyanide complex anions, respectively. A few of the hexa-cyanoferrate salts have found major commercial applications. Probably, the most important among them is ferric ferrocyanide, FeFe(CN)e, also known as Prussian blue. The names, formulas and the CAS registry numbers of some hexacyanoferrate complexes are given below. Prussian blue and a few other important complexes of this broad class of substances are noted briefly in the following sections ... 

Thompson DF, Called ED Soluble or insoluble Prussian blue for radiocesium and thallium poisoning Ann Pharmacother 2004 38 1509. [PMID 15252192]... 

He describes two blue printing inks the one Is made by taking the soluble Prussian blue obtained in the manufacture of Ms blue writing ink, and rubbing it up with oil or, by triturating with oil the residue obtained by evaporating his blue ink. 

For tho second blue Ink, he prepares the soluble Prussian blue with bromine instead of iodine, and diffuses it in oil. 

Prussian blue is regarded as a compound of three equivalents of ferroeyanogen with two of iron, and its composition is therefore expressed by the formula 8 Cfy -j- 2 Fea, or Fe, Cys, It is formed whenever a salt of sesquioxide of iron is added to a soluble metallio ferrocyanide. The usual method is to precipitate a solution of sesquiehloride or sesquinitrate of iron by ferrocyanide of potassium and In point qf fact a very important part of its manufacture consists in the preparation of this latter salt, which will now be described. 

FeCl3, dark blue precipitate—Prussian blue, Fe4 Fe(CN)6 3, insoluble in HO, soluble in oxalic acid. 

Alkali or alkaline-earth salts of both complexes are soluble in water (except for Ba2[Fe(CN)6]) but are insoluble in alcohol. The salts of hexakiscyanoferrate(4—) are yellow and those of hexakiscyanoferrate(3—) are mby red. A large variety of complexes arise when one or more cations of the alkali or alkaline-earth salts is replaced by a complex cation, a representative metal, or a transition metal. Many salts have commercial applications, although the majority of industrial production of iron cyanide complexes is of iron blues such as Prussian Blue, used as pigments (see PIGMENTS, inorganic). Many transition-metal salts of [Fe(CN) J4"" have characteristic colors. Addition of [Fe(CN)6]4 to an unknown metal salt solution has been used as a qualitative test for those transition metals. 

All of the [Fe(CN) J4- salts may be considered salts of ferrocyanic acid or tetrahydrogen hexakiscyanoferrate [17126-47-5], H4[Fe(CN)J, a strongly acidic, air-sensitive compound. It is soluble in water and alcohol but is insoluble in ether. It can be prepared by precipitation of an etherate by adding ether to a solution of [Fe(CN) J4"" that was acidified with concentrated sulfuric acid. Removal of the ether of solvation affords a white powder which is stable when dry but slowly turns blue in moist air because of Prussian Blue formation. 

I. Luiz de Mattos and M. Carneiro da Cunha Areias, Automated determination of glucose in soluble coffee using Prussian Blue-glucose ox-idase-Nafion modified electrode, Talanta, 66(5) (2005) 1281-1286. 

Other Papers.—Various iron species prepared by the vacuum pyrrolysis of acetyl-ferrocene-furfural resins at 400°C have been studied by Mossbauer spectroscopy. These consist of an amorphous glass-like carbon matrix containing free iron atoms, Fe+ ions, iron clusters, superparamagnetic iron, and ferromagnetic iron.333 The effect of pressure of up to 50kbar on the absorption spectra of five iron(m), two iron(n) and one mixed valence compound has been studied. In six of the compounds, but not in basic ferric acetate or soluble Prussian Blue, the observed pressure-induced bands were assigned to d-d transitions of converted iron(n) for the ferric compounds and to spin-forbidden d-d bands for the ferrous compounds. The charge-transfer band from iron(n) to iron(m) in soluble Prussian Blue showed a blue shift at pressures up to 7.2 kbar.334... 

Electrochromic materials are of three basic types [i]. In a given -> electrolyte solution, type I materials are soluble in both the reduced and oxidized (redox) states, an example being l,l -di-methyl-4,4 -bipyridylium ( methyl viologen ), which, on reduction, switches from the colorless di-cation to the blue radical cation. Type II materials are soluble in one redox state, but form a solid film on the surface of an electrode following electron transfer. An example here is l,l -di-heptyl-4,4 -bipyridylium ( heptyl viologen ). In type III materials, such as -> tungsten oxide, - Prussian blue, and electroactive conjugated polymers, both... 

Prussian blue — iron(III) hexacyanoferrate(II) is the archetype of sparingly soluble mixed valence polymeric metal hexacyanometalates with the formula Me Me(N) [Me c (CN)6] with (i), (N), and (C) indicating the position in the crystal lattice, where (i) means interstitial sites, (N) means metal coordinated to the nitrogen of the cyanides, and (C) means metal ions coordinated to the carbon of the cyanides. It is one of the oldest synthetically produced coordination compounds and was widely used as pigment in paints because of the intensive blue color. The compound has been studied extensively by electrochemical and other methods. The importance of Prussian blue in electrochemistry is related to the fact that it has two redox-active metal centers and that it has an open structure that allows small cations to... 

Potassium ruthenocyanide crystallises in square pseudo-rhombic plates, isomorphous with the corresponding ferro- and osmo-cyanides.2 Its solution in water yields no precipitate with salts of the alkaline earth metals as their ruthenocyanides are soluble. Ferric chloride gives a rich purple precipitate resembling Prussian blue in its chemical properties. Soluble in pure w ater it is precipitated by salts or alcohol. When precipitated in cotton fibre it adheres well, imparting its own beautiful colour. Alkalies decompose the salt, which, however, is re-formed on addition of dilute acid. This constitutes a useful test for ruthenocyanides. 

Figure 4 The structure of Prussian blue and related compounds. If none of the cube centre sites are occupied, the structure is that of ferric ferricyanide (both black and white Fe positions occupied by Fe111) if every second cube centre site (marked with a dotted circle) is occupied by K+, the structure is that of soluble Prussian blue (black = Fe11, white = Fe111) if all the centre sites are occupied by K+ (crosses as well as dotted circles) the structure is that of dipotassium ferrous ferrocyanide...

If iron(III) chloride is added to an excess of potassium hexacyanoferrate(II) a product with the composition of KFe[Fe(CN)6] is formed. This tends to form colloid solutions ( Soluble Prussian Blue ) and cannot be filtered. 

When a solution of potassium ferrocyanide reacts with rather less than one equivalent of a ferric salt, a blue hydrated precipitate of a-soluble Prussian blue, or ferric potassium ferrocyanide Fe K[Fe (CN)6], is obtained. Now, Hofmann and his co-workers 5 have shown that this precipitate is identical with that prepared under precisely similar conditions by the addition of a ferrous salt to potassium fcrricyanide, although in this case ferrous potassium ferricyanide, Fe K[Fe (CN)6], might be expected. It is therefore assumed that the latter salt is unstable, and, at the moment of formation, undergoes intramolecular rearrangement to the former complex. 

Calcium ferrocyanide, Ca2Fe(CN)e.dH20 (where =11,5 or 12,6), may be obtained by boiling Prussian blue with the calculated quantity of milk of lime. It is also formed when hydrogen cyanide is passed into a suspension of lime and ferrous hydroxide in water. The salt crystallises m pale yellow triclinic prisms, which are more soluble in cold water than in hot. 

The Prussian Blues.—Several of these are known, namely a soluble Prussian blue, 4Fe K[Fe (CN)6].7H20. This compound is obtained when a solution of potassium ferrocyanide interacts with rather less than one equivalent of a ferric salt.6 It occurs as a deep... 

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