Potassium iron hexacyanoferrate —

Potassium iron hexacyanoferrate —see Prussian blue Potassium peroxodicarbonate... 

Lead(II) azide Lead chromate Lead dioxide Calcium stearate, copper, zinc, brass, carbon disulfide Iron hexacyanoferrate(4-) Aluminum carbide, hydrogen peroxide, hydrogen sulfide, hydroxylamine, ni-troalkanes, nitrogen compounds, nonmetal halides, peroxoformic acid, phosphorus, phosphorus trichloride, potassium, sulfur, sulfur dioxide, sulfides,... 

A paradigmatic example is provided by an extensively used pigment Pmssian blue— potassium-iron(III) hexacyanoferrate(II), also called potassium-iron(III) fer-rocyanide. This is constituted by potassium-iron(III) ferrocyanide, KFe[Fe(CN)g], whose electrochemistry has been extensively studied [74-77],... 

Another candidate for the first coordination compound is Prussian Blue, potassium iron(III) hexacyanoferrate(II), a complex of empirical formula KCN-Fe(CN)2- Fe(CN)3. It was first obtained accidentally in 1704 by Diesbach, a manufacturer of artist s colors from Berlin. Initially it was described9 as a nontoxic pigment suitable for oil colors, but its method of preparation was kept secret, probably because Diesbach wished to benefit monetarily from his discovery. 

Iron (II) sulfate (aq) White precipitate of potassium iron (II) hexacyanoferrate, which turns blue by oxidation... 

Yellowish brown precipitate of iron (II) cyanide soluble in excess reagent, forming the hexacyanoferrate (II) ion In complete absence of air, white precipitate of potassium iron (II) hexacyanoferrate if air is present, a pale blue precipitate is formed... 

Potassium hexacyanoferrate(II) solution in the complete absence of air a white precipitate of potassium iron(II) hexacyanoferrate(II) is formed ... 

Hexa.cya.no Complexes. Ferrocyanide [13408-63 ] (hexakiscyanoferrate-(4—)), (Fe(CN) ) , is formed by reaction of iron(II) salts with excess aqueous cyanide. The reaction results in the release of 360 kJ/mol (86 kcal/mol) of heat. The thermodynamic stabiUty of the anion accounts for the success of the original method of synthesis, fusing nitrogenous animal residues (blood, horn, hides, etc) with iron and potassium carbonate. Chemical or electrolytic oxidation of the complex ion affords ferricyanide [13408-62-3] (hexakiscyanoferrate(3—)), [Fe(CN)g] , which has a formation constant that is larger by a factor of 10. However, hexakiscyanoferrate(3—) caimot be prepared by direct reaction of iron(III) and cyanide because significant amounts of iron(III) hydroxide also form. Hexacyanoferrate(4—) is quite inert and is nontoxic. In contrast, hexacyanoferrate(3—) is toxic because it is more labile and cyanide dissociates readily. Both complexes Hberate HCN upon addition of acids. 

The Stock Oxidation-Number System. Stock sought to correct many nomenclature difficulties by introducing Roman numerals in parentheses to indicate the state(s) of oxidation, eg, titanium(II) chloride for TiCl2, iron(II) oxide for FeO, titanium(III) chloride for TiCl, iron(III) oxide for Fe203, titanium(IV) chloride for TiCl, and iron(II,III) oxide for Fe O. In this system, only the termination -ate is used for anions, followed by Roman numerals in parentheses. Examples are potassium manganate(IV) for K2Mn02, potassium tetrachloroplatinate(II) for K PtCl, and sodium hexacyanoferrate(III) for Na3Fe(CN)3. Thus a set of prefixes and terminations becomes uimecessary. 

FIGURE 16.16 When potassium cyanide is added to a solution of iron(ll) sulfate, the cyanide ions replace the H.O ligands of the [Fe(H20), - + complex (left and produce a new complex, the hexacyanoferrate(ll) ion, Fe(CN)(l 4 (right). The blue color is due to the polymeric compound called Prussian blue, which forms from the cyanoferrate ion. 

When oxidized by iron(III) ions 4-aminoantipyrine reacts with phenols to yield colored quinonoid derivatives (cf. 4-aminoantipyrine — potassium hexacyanoferrate(III) reagent in Volume 1 a). It is an oxidative coupling based on the Emerson reaction. 

In both research and practice, critical localised concentrations of metal contamination can be difficult to detect. Potassium hexacyanoferrate(II) (10.80) gives an intense deep blue coloration with iron(III), permitting extremely sensitive detection of tiny iron spots even by visual inspection. It is recommended as a quality control measure on batches of cotton destined for bleaching [237]. However, in view of the random distribution of metal traces, even the most sensitive test cannot guarantee freedom from contamination throughout a batch of goods to be bleached. 

The effects of various metal oxides and salts which promote ignition of amine-red fuming nitric acid systems were examined. Among soluble catalysts, copperQ oxide, ammonium metavanadate, sodium metavanadate, iron(III) chloride (and potassium hexacyanoferrate(II) with o-toluidine) are most effective. Of the insoluble materials, copper(II) oxide, iron(III) oxide, vanadium(V) oxide, potassium chromate, potassium dichromate, potassium hexacyanoferrate(III) and sodium pentacyanonitrosylferrate(II) were effective. 

Iron Blue, Cl Pigment Blue 27, which has been known by various names over the years, perhaps the best known being Prassian Blue, is ferric ammonium ferricyanide, FeNH Fe(CN)g(xH20. The hrst step in its preparation involves the precipitation of complex iron(ii) cyanides, e.g. potassium hexacyanoferrates(ii) with iron(i) salts, e.g. the sulfate or chloride, in an aqueous solution in the presence of ammonium... 

To extract the iron(III) ions, pass 20 ml of a hot 2 M hydrochloric acid solution through the cation exchanger. Gather the solution flowing out from the column in a 250-ml flask. Use the reaction with potassium hexacyanoferrate(II) to check for the completeness of iron extraction. 

Pour 1-2 ml of an iron(III) chloride solution into each of two test tubes. Add several drops of an ammonium thiocyanate solution to one of the tubes, and a potassium hexacyanoferrate(II) (potassium ferrocyanide) solution to the other one. What happens Write the equations of the reactions. What are these reactions used for ... 

Concentrated sulfuric acid Silver nitrate Copper sulfate Mercury (II) chloride Methylene blue Potassium hexacyanoferrate (II) and iron (II) sulfate Fast evolution of sulfur dioxide and precipitation of pale yellow sulfur Black precipitate of silver Red precipitate of copper Gray precipitate of mercury Decolorization in cold solution White precipitate of dipotassium iron (II) hexacyanoferrate (II) turns from white to Prussian blue... 

The formula for potassium arsenate is K3As04. The formula for potassium ferrocyanide, systematically called potassium hexacyanoferrate(II), is K4Fe(CN)g. Write the formulas for (a) calcium arsenate ib) iron(III) arsenate ... 

Potassium cyanide solution (POISON) yellowish-brown precipitate of iron(II) cyanide, soluble in excess reagent when a pale-yellow solution of hexacyanoferrate(II) (ferrocyanide) [Fe(CN)6]4- ions is obtained ... 

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