Ammonium ferrocyanide

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 ... 

Ferric ammonium ferrocyanide—The blue pigment obtained by oxidising under acidic conditions with sodium dichromate the acid-digested precipitate resulting from mixing solutions of ferrous sulfate and sodium ferrocyanide ia the presence of ammonium sulfate. The oxidized product is filtered, washed, and dried. The pigment consists principally of ferric ammonium ferrocyanide with small amounts of ferric ferrocyanide and ferric sodium ferrocyanide. 

Ferric ammonium citrate molecular formula, 6 6381 solubility in water, 6 649t Ferric ammonium ferrocyanide pigment used in makeups, 7 836t Ferric bromide, physical properties of,... 

Other inorganic crystals studied by Mark and his collaborators, sometimes leading to complete structure determinations, include strontium chloride, zinc hydroxide, tin tetraiodide, potassium chlorate, potassium permanganage, and ammonium ferrocyanide. Minerals investigated by them include CaSO (anhydrite), BaSO (barite), PbSO, Fe2TiO[j (pseudobrookite), and three forms of Al2Si05 (cyanite, andalusite, and sillimanite). 

Copper(ll) nitrate, being an oxidizing agent, can undergo violent reactions with readily oxidizahle substances. Reaction with acetic anhydride is violent, and heating with potassium or ammonium ferrocyanide at 220°C may cause an explosion. It can ignite paper on prolonged contact. 

Autopurification A wet-scrubbing process for removing hydrogen sulfide from coke-oven gas. The scrubbing liquor was an ammoniacal suspension of ferric ammonium ferrocyanide. The process was developed by ICI, Billingham, UK, in the 1930s and 40s, but was abandoned in 1947. 

Ammonium ferrocyanide and ferricyanide.—The modes of preparation and the properties of ammonium ferrocyanide and ferricyanide are described in Vol. IX., Part II. 

When ammonium ferrocyanide, or its double compound with ammonium chloride, is heated, a black magnetic powder is obtained. This, upon ignition in air, is completely transformed into ferric oxide without any change in weight, and is believed 2 to be the dicarbide, FeC2. 

Aluminium ammonium ferrocyanide, Al(NH4)Fe(CN)6.4H20, is formed as a jelly on mixing equivalent solutions of aluminium chloride and ammonium ferrocyanide.6 The salt is difficult to isolate, but is obtained as a precipitate by centrifugating at 3000 revolutions per minute. The precipitate is washed with acetone and ether and dried in vacuo. It resembles the potassium salt in appearance, being dark green and transparent m lumps, but a light bluish green when powdered. At 100° C. it becomes anhydrous and assumes a deep blue colour. 

The double salt with ammonium chloride, (NH4)4Fe(CN)6.NH4Cl. 3H20, is obtained as pale yellow or brown crystals by cooling warm, mixed solutions of ammonium ferrocyanide and ammonium chloride in the presence of sodium cyanide or of acetic acid respectively.11 The anhydrous salt has also been obtained.8... 

Calcium ammonium ferrocyanide, (NH4)2CaFe(CN)6, results on mixing cold concentrated solutions of calcium chloride and ammonium ferrocyanide, in equimolecular proportions, washing the precipitate and drying in air or at 100° C. It also results on boiling potassium calcium ferrocyanide (see p. 219) with water containing a large excess of ammonium chloride.7... 

Cerium ammonium ferrocyanide, (NH4).CeFe(CN)6, is obtained8 on mixing, in the cold, concentrated solutions of cerium chloride and ammonium ferrocyanide. No description of the salt has been given. 

Ammonium cuproferrocyanide, (NH4)2Cu2Fe(CN)6, results1 when cuprous cyanide is boiled with a solution of ammonium ferrocyanide containing ammonium sulphite, and hydrogen passed through the mixture. It may also be obtained by double decomposition of the sodium salt with ammonium nitrate. It crystallises in small, colourless six-sided prisms, which readily decompose both under water and on mere exposure to air or in a vacuum. 

Ammonium cupriferrocyanide, (NH4)2CuFe(CN)e, is prepared 1 by boiling a mixed solution of cupric and ammonium ferrocyanides. It crystallises in brownish red cubes, and is best dried in a vacuum over sulphuric acid. The following four salts are obtained in an analogous manner —... 

Magnesium ammonium ferrocyanide, Mg(NH4)2Fe(CN)6, is obtained3 by mixing concentrated solutions of magnesium chloride and ammonium ferrocyanide in equivalent proportions. The anhydrous salt separates out as small white crystals which remain unaltered at 120° C. A saturated solution of the salt contains 2 48 grams per litre. 

Ferric ammonium ferrocyanide, FeNH4[Fe(CN)6], results when potassium ferrocyanide is heated with a solution of hydroxylamine hydrochloride. It is a deep blue insoluble powder.7 The hydrated salt FeNH4[Fe(CN)6].H20 is known as Monthiers9 blue,8 having been obtained by Monthier as the result of oxidising the white precipitate thrown down by the action of potassium ferrocyanide upon ammoniacal ferrous chloride solution. It may also be prepared by dissolving iron wire in a solution containing ammonia, ammonium chloride, and... 

The redox chemistry of the Prussian blue family (Table 7) has attracted considerable attention. The generation of thin films of Prussian blue has led to studies of its mediation in electron transfer reactions and of the electrochemical processes involved in its deposition and redox reactions. This work has been spurred by its electrochromic properties which have been used in prototype electronic display devices based, for example, on Prussian blue modified Sn02 electrodes. A recent review deals with the electrochemistry of electrodes modified by depositing thin films of PB and related compounds on them. Interestingly, true Prussian blue is somewhat difficult to process and modern iron blue pigments such as Milori blue are derived from the oxidation of rlin white Fe(NH4)2[Fe(CN)e] to give iron(III) ammonium ferrocyanides. 

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