Hydrogen ferrocyanide

As has already been mentioned, hydrogen ferrocyanide, when... 

Hydrogen ferrocyanide, Ferro-cyanic acid, H4[Fe(CN)6], is conveniently prepared by adding concentrated aqueous hydrogen chloride solution to a saturated solution of potassium ferrocyanide, m the cold —... 

Hydrogen ferrocyanide is soluble in water and possesses a strong acid reaction. The solution decomposes on boiling, evolving gaseous hydrogen cyanide, and yielding a white precipitate of ferrous cyanide. Thus —4... 

Caesium ferrocyanide, Cs4Fe(CN)6+( )6H20, has been prepared by neutralising hydrogen ferrocyanide with caesium hydroxide.4... 

Concentrated sulphuric acid dissolves dry anhydrous potassium ferrocyanide, yielding potassium hydrogen sulphate and hydrogen ferrocyanide —... 

Strontium ferrocyanide, Sr2Fe(CN)6.14H205 is obtained as a soluble salt by neutralising hydrogen ferrocyanide with the hydroxide or carbonate of strontium. The salt crystallises in monoclinic prisms containing 14 molecules of water,3 of which seven are lost on exposure to air and a further six when kept over concentrated sulphuric acid. 

Ferrous hydrogen ferrocyanide, H2Fe[Fe(CN)6], results when hydrogen ferrocyanide solution is heated to 110°-120° C.4 with exclusion of air. It readily oxidises to ferric hydrogen ferrocyanide, Fe H[Fe (CN)6].H20, which is a blue compound, insoluble in water, oxalic acid, and ammonium oxalate solutions. 

Ferrous ferrocyanide, Fe2[Fe(CN)6], is formed when an aqueous solution of hydrogen ferrocyanide is heated until hydrogen cyanide ceases to be evolved.6... 

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). 

A wide variety of enzymes have been used in conjunction with electrochemical techniques. The only requirement is that an electroactive product is formed during the reaction, either from the substrate or as a cofactor (i.e. NADH). In most cases, the electroactive products detected have been oxygen, hydrogen peroxide, NADH, or ferri/ferrocyanide. Some workers have used the dye intermediates used in classical colorimetric methods because these dyes are typically also electroactive. Although an electroactive product must be formed, it does not necessarily have to arise directly from the enzyme reaction of interest. Several cases of coupling enzyme reactions to produce an electroactive product have been described. The ability to use several coupled enzyme reactions extends the possible use of electrochemical techniques to essentially any enzyme system. 

Other solutions to dealing with interferences in the detection of H O have included the use of a copperfll) diethyldithiocarbamate precolumn to oxidize the sample before it reaches the immobilized enzyme, as well as the use of a palladium/gold sputtered electrode which catalyzes the oxidation of hydrogen peroxide In addition, peroxidase has been used to catalyze the reaction between hydrogen peroxide and iodide ferrocyanide and organo-fluorine compounds Am-... 

The electrochemical rate constants for hydrogen peroxide reduction have been found to be dependent on the amount of Prussian blue deposited, confirming that H202 penetrates the films, and the inner layers of the polycrystal take part in the catalysis. For 4-6 nmol cm 2 of Prussian blue the electrochemical rate constant exceeds 0.01cm s-1 [12], which corresponds to the bi-molecular rate constant of kcat = 3 X 103 L mol 1s 1 [114], The rate constant of hydrogen peroxide reduction by ferrocyanide catalyzed by enzyme peroxidase was 2 X 104 L mol 1 s 1 [116]. Thus, the activity of the natural enzyme peroxidase is of a similar order of magnitude as the catalytic activity of our Prussian blue-based electrocatalyst. Due to the high catalytic activity and selectivity, which are comparable with biocatalysis, we were able to denote the specially deposited Prussian blue as an artificial peroxidase [114, 117]. 

Another mode of SOD prooxidant activity has been proposed by Offer et al. [9]. In 1973, Rotilio et al. [10] showed that SOD can readily oxidize ferrocyanide. Offer et al. [9] found that low SOD concentrations inhibited superoxide-induced oxidation of ferrocyanide, but SOD becomes prooxidative at higher concentrations. As this reaction did not require hydrogen peroxide, it was suggested that the prooxidant effect of enhanced SOD concentrations might be explained by decreasing the steady state of superoxide and the direct oxidation of ferrocyanide by SOD. 

Fischer A process for removing hydrogen sulfide from coal gas by absorption in an aqueous solution of potassium ferrocyanide and bicarbonate the solution is regenerated electro-chemically with the production of elemental sulfur. Operated at the Hamburg gasworks in the 1930s. 

Prussian blue (inorgchem) Fe4 Fe(CN)6 3 Ferric ferrocyanide, used as a blue pigment and in the removal of hydrogen sulfide from gases. prash an blu j prussic acid See hydrocyanic acid. pras ik as ad ... 

Potassium Chlorate. .. Potassium Triiodo Mercurate(ll) Potassium Chloride Potassium Chlorate Potassium Chromate Potassium Cyanide Potassium Dichromate Potassium Ferricyanide Potassium Ferrocyanide Potassium Fluoride Potassium Formate Potassium Hydride Potassium Hydrogen Phthalate Potassium Hydroxide Potassium lodate... 

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