Mercuric ferrocyanide

Mercuric ferrocyanide, Hg2Fe(CN)6,7 is white m appearance. Chlorine water turns it green, and bromine water brown. 

Potassium mercuric ferrocyanide, K2HgFe(CN)6, may be obtained as a faintly blue powder by the interaction of mercuric chloride and potassium ferrocyanide solutions.4 It is insoluble in water, but is decomposed by acids. 

Chemical complexes of various transition metals have been shown to promote N-nitrosation (28). These metal complexes include ferrocyanide, ferricyanide, cupric ion, molybate ion, cobalt species, and mercuric acetate. All of the reactions are thought to proceed by oxidation-reduction mechanisms. However, such promotion may not be characteristic of transition metal complexes in general, since ferricyanide ion has been shown to promote nitrosation in metalworking fluids, whereas ferric EDTA does not (2 0). Since the metalworking operation generates metal chips and fines which build up in the fluids, this reaction could be of significance in the promotion of nitrosamine formation in water-based metalworking fluids. 

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... 

Occluded hydrogen is more reactive chemically than the normal gas. Hydrogenated palladium precipitates mercury and mercurous chloride from an aqueous solution of the dichloride, without any evolution of hydrogen. It reduces ferric salts to ferrous potassium ferricyanide to ferrocyanide chlorine water to hydrochloric add iodine water to hydriodic acid 2 chromates to chromic salts ceric to cerous salts whilst cupric, stannic, arsenic, manganic, vanadic, and molybdic compounds are also partially reduced.3... 

A series of stable salts has been prepared 8 containing mercuric cyanide associated with the ferrocyanide molecule. The first to be discovered was the potassium salt, K4Fe(CN)6.3Hg(CN)2.4H20, by Kane,7 which is readily obtained by allowing a mixed solution of potassium ferrocyanide and mercuric cyanide to evaporate. Other salts in this series are those of... 

The direct method of potentionietric titration has been applied to various precipitation reactions, among which may be mentioned the determination of magnesium in dolomite 23 the precipitation of zinc with ferrocyanide 24 and the titration of chloride, bromide and thiocyanate 25 with mercurous perchlorate 20... 

Fbrric—Are acid, and yellow or brown. (1.) Potash, or ammonium hydroxid voluminous, red-brown ppt. insoluble in excess. (2.) Hydrogen sulfid in acid solution milky ppt. of sulfur ferric reduced to ferrous compound. (8.) Ammonium sulfhydrate black ppt. insoluble in excess soluble in acids. (4.) Potassium ferrocyanid dark blue ppt. insoluble in HCl sohible in KHO. <5.) Potassium sulfocyanate dark-red color prevented by tartaric or citric acid discharged by mercuric chlorid. (6.) Tannin blue-black color. 

Pyridine is a tertiary amine its aqueous solution shows an alkaline reaction and precipitates the hydroxides of metals, some of which are soluble in an excess of the amine. Salts of pyridine like those of other amines form characteristic double salts with metallic halides. The ferrocyanide of pyridine and the addition-product of pyridine and mercuric chloride are difficultly soluble in water these compounds are used in the purification of the base. Pyridine is a very stable compound it can be heated with nitric acid or chromic acid without undergoing change but at 330° it is converted by a mixture of nitric acid and fuming sulphuric acid into nitropyridine, a colorless compound that melts at 41° and boils at 216°. At a high temperature pyridine is converted into a sulphonic acid by sulphuric acid. Chlorine and bromine form addition-products, e.g., C5H5N.CI2, at the ordinary temperature when these are heated to above 200°, substitution-products are formed. The hydroxyl derivative of pyridine is made by fusing the sulphonic acid with sodium hydroxide it resembles phenol in chemical properties. The three possible carboxyl derivatives of pyridine are known. The a-acid is called picolinic acid, the jS-acid nicotinic acid (664), and the 7-acid isonicotinic acid. 

White precipitates are formed when a 1% solution of cusparine is treated with phosphotungstic, phosphomolybdic or tannic acids, or with mercuric chloride or potassium mercuri-iodide. Picric acid, platinic chloride or potassium chromate give yellow precipitates, auric chloride or potassium bismuth iodide brown, and potassium ferrocyanide bluish-white (36). By treating a solution of cusparine hydrobromide with bromine water, a series of bromocusparine polybromides is obtiuned(38). 

Ferricyanide ions are demasked in analogous fashion by mercuric chloride and iron+ ions are set free. However, this does not detract from the detection of ferrocyanide because a,ct -dip5n idyl reacts only with iron+ ions. 

Thiocyanates and/or iodides interfere with the sensitive Pmssian blue test for ferrocyanides when carried out in a micro test tube or on a spot plate. There is simultaneous formation of red ferrithiocyanate or free iodine, which interfere with the decisive detection of small amounts of Prussian blue. If, however, the test is carried out on filter paper impregnated with ferric chloride, no difficulty is experienced because of thiocyanates or iodides. A capillary separation succeeds through the fact that ferric thiocyanate is readily decomposed by mercuric chloride, sodium fluoride, or sodium thiosulfate. If there is danger of interference by ferricyanide, the second procedure should be followed. 

A far better sensitivity is attained for the detection of ferrocyanide in the presence of thiocyanate when use is made of the fact that ferric thiocyanate is decomposed by mercuric chloride (formation of [Hg(CNS)4] ions), sodium fluoride (production of [FeFe] ions), or sodium thiosulfate (reduction to Fe+ ions). 

Procedure. ( ) When a drop of a solution containing considerable thiocyanate is placed on paper impregnated with ferric chloride, only a deep red fleck is seen. If spotted with a solution of mercuric chloride, sodium fluoride, or sodium thiosulfate, the red color due to the ferric thiocyanate is discharged. The circle or ring of Prussian blue, due to ferrocyanide, is readily visible on the paper, which is now white. 

The tendency of mercuric ions to form water-soluble, undissociated mercuric cyanide is so great that they are able to liberate ferrous ions from ferrocyanide ions. If this demasking occurs in the presence of a,a -dipyridyl, a red color appears because of the formation of [Fe(a,a -Dip)3]+2 ions. (See pages 263-265.) The underl)dng reactions are ... 

The color reaction with thiocyanate is not suitable for the detection of iron in the presence of large amounts of mercury salts because the thiocyanate ion is consumed in the formation of slightly dissociated mercuric thiocyanate, or of double thiocyanates of mercury. The Prussian blue reaction is uncertain, owing to the formation of yellow mercury ferrocyanide. The a,a -dipyridyl test as given here may be used (see page 263). 

Iron percfiloride and potassium sulphocyanide give a blood-red, decolourized by mercuric chloride potassium sulphocyanide and sulphuric acid a fine old port colour, cleared by the same agent Litmus solution and an acid produce red, also permanganate of potash and sulphuric acid, cleared by hyposulphite of soda. Potassium ferrocyanide and the double sulphate of uranium and potassium give an old port-like colour-washing soda clears it. 

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