Cyanide ferrocyanide

Ferrocyanid, n. ferrous cyanide, iron(II) cyanide ferrocyanide. 

Carbon monoxide (test inflammability) on heating, no charring— formate, cyanide, ferrocyanide, ferricyanide. 

A still more favourable effect upon current efficiency is achieved if certain substances such as fluorides are added, which raise the potential by some hundredths or even tenths of a volt. Other compounds such as chlorides, eyanides (potassium cyanide, ferrocyanide or ferricyanide) or thiocyanates have a double effect on one hand they decompose the Caro s acid and on the other hand they raise the anode potential. Ammonium thiocyanate is almost generally used. It reduces Caro s acid, at first, and changes it into sulphuric acid and hydrogen cyanide, the latter promoting a rise in the anode potential. 

Potassium hydroxide, like its sodium counterpart, is a versatile intermediate in the production of chemicals. Because KOH is more expensive, NaOH dominates in large-scale uses, and potassium chemicals are largely restricted to specialty markets. They are often more soluble and more reactive than the corresponding sodium chemicals, and this fact is responsible for many of their applications. Widely used derivatives include acetate, bicarbonate, bromide, cyanide, ferrocyanide, oxalate, permanganate, and phosphate. The derivative with the greatest market probably is potassium carbonate, which is discussed in Section 7.5.2.2A. 

Fleischmann, M., Graves, F.R. and Robinson, J. (1985) The Raman spectroscopy of the ferri-cyanide/ferrocyanide system at gold, -palladium hydride and platinum electrodes. Journal of Electroanalytical Chemistry, 182, 87. 

There is no interference from chlorides, bromides, iodides, thiocyanates, cyanides, ferrocyanides, iodates, chlorates, nitrates, nitrites, phosphates, carbonates, sulfates, sulfites, thiosulfates and sulfides. The interfering action of chromates, periodates, persulfates and fenicyanides can be prevented by reduction by heating with an excess of sulfite. 

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. 

Cyanide iron blues can be prepared by several methods. The most common one is the indirect, two-step process. In the first step, a white precipitate (Berlin white), is produced by the reaction of sodium, potassium, or ammonium ferrocyanide and ferrous sulfate ... 

Calcium cyanamide can be converted to calcium cyanide [592-01-8], used ia cyanidation of metallic ores and production of sodium cyanide and ferrocyanides (11) (see Cyanides). Calcium cyanamide has also been used to make cyanamide which ia turn is the starting material for important iadustrial organic syntheses. 

Sodium chloride and sodium cyanide are isomorphous and form an unintermpted series of mixed crystals. The ferrocyanide ion has a marked effect on the habit of sodium cyanide crystallized from aqueous solution (50). Sodium cyanide and sodium carbonate form a molten eutectic at approximately 53 wt % sodium carbonate and 465°C. The specific conductivity of molten 98% sodium cyanide is 1.17 S /cm (51). 

A solution of sodium cyanide shaken with freshly precipitated ferrous hydroxide is converted to a ferrocyanide ... 

If the solution is acidified and aUtde ferric sulfate added, ferric ferrocyanide [14038-43-8], Fe4[Fe(CN)g]2, is produced. This salt has a characteristic deep blue color, and the reaction may be used to test for the cyanide. 

Potassium cyanide [151 -50-8] KCN, a white crystalline, deUquescent soHd, was initially used as a flux, andlater for electroplating, which is the single greatest use in the 1990s. The demand for potassium cyanide was met by the ferrocyanide process until the latter part of the nineteenth century, when the extraordinary demands of the gold mining industry for alkah cyanide resulted in the development of direct synthesis processes. When cheaper sodium cyanide became available, potassium cyanide was displaced in many uses. With the decline in the use of alkah cyanides for plating the demand for potassium cyanide continues to decline. The total world production in 1990 was estimated at about 4500 t, down from 7300 t in 1976. 

Ammonium cyanide may be prepared in solution by passing hydrogen cyanide into aqueous ammonia at low temperatures. It may also be prepared from barium cyanide and ammonium sulfate, or calcium cyanide with ammonium carbonate. It may be prepared in the dry state by gentiy heating a mixture of potassium cyanide or ferrocyanide and ammonium chloride, and condensing the vapor in a cooled receiver. Ammonium cyanide is soluble in water or alcohol. The vapor above soHd NH CN contains free NH and HCN, a very toxic mixture. 

The use of black cyanide as a fumigant and rodenticide makes use of the atmospheric humidity action that Hberates hydrogen cyanide gas. It can only be used effectively ia confined spaces where hydrogen cyanide builds up to lethal concentrations for the particular appHcation. Black cyanide is also used ia limited quantities ia the production of pmssiates or ferrocyanides (see Iron compounds). 

Cyaneisen, n. iron cyanide, -kalium, n. potassium ferrocyanide, -verbindungt /. iron cyanogen compound, specif, a ferrocyanide. 

Ferrifeiro-cyanid, n. ferric ferrocyanide (Prussian blue), -jodid, n. ferroeoferric iodide, -oxyd, n. ferroeoferric oxide, iron(II,III) oxide. 

The complex cyanides of transition metals, especially the iron group, are very stable in aqueous solution. Their high co-ordination numbers mean the metal core of the complex is effectively shielded, and the metal-cyanide bonds, which share electrons with unfilled inner orbitals of the metal, may have a much more covalent character. Single electron transfer to the ferri-cyanide ion as a whole is easy (reducing it to ferrocyanide, with no alteration of co-ordination), but further reduction does not occur. 

Ferrous ion, iron(II), forms a complex with six cyanide ions, CN- the octahedral complex is called ferrocyanide. Ferric ion, iron(III), forms a complex with six cyanide ions the octahedral complex is called ferricyanide. Write the structural formulas for the ferrocyanide and the ferricyanide complex ions. 

K Salt. A yellow cryst solid, prepd by the action of basic K salts on TeNMe in the presence of reducing agents (see also above under TNMe). Some which have been used are K methoxide in me ale (this proc is subject to dangerous expins) (Ref 8) K cyanide in me ale (Ref 23) a satd aq soln of K ferrocyanide (Ref 9) or K nitrite in w, yield 80% (Ref 38). It has also been prepd by the action of K nitrite on dibromodinitromethane (Ref 13). Its expln temp is 97-98° (Ref 3) and its impactg sensy, using a noisemeter to detect explns, was found to... 

The ion-triplet oxidises I in the slow step to yield -Iz . The non-participation of any ligand substitution step is confirmed by the absence of any incorporation of activity from added C-labelled free cyanide ion into the product ferrocyanide ... 

Wiberg et have performed the reaction in the presence of C-labelled cyanide ion and find no incorporation of activity into product ferrocyanide. Evidently the reversible ligand displacement proposed by the Czech workers does not take place and the electron-transfer scheme of Swinehart is preferable. Recent spectroscopic studies indicate that a complex [Fe(CN)5(CNS03)] functions as an intermediate in this reaction. 

For a given carbonium ion the order of degree of ionization appears to be hydroxide, alkoxides, and carboxylates < cyanide < thiocyanate < ferrocyanide < azide < chloride < bromide < sulfate and perchlorate. 

Erlenmeyer An early process for making potassium cyanide from potassium ferrocyanide by heating it with sodium ... 

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