Potassium cobalt nitrite

L, L. Burgess and 0. Kamm showed that the corresponding disodium potassium cobaltic nitrite, NaK2Co(N02)6, can also be made. Lithium cobaltic hexanitrite, Li3Co(N02)6, and ammonium cobaltic hexanitrite, (NH4)3Co(N02)6.l H20, were prepared by 0. W. Gibbs and T. A. Genth, 0. L. Erdmann, S. P. Sadtler, W. C. Ball and H. H. Abram, and A. Rosenheim and I. Koppel. 

Potassium Cobaltous Nitrite, 2KN02.Co(N02)2. H20, is obtained by adding potassium nitrite to a neutral solution of cobalt chloride. It is precipitated as a yellow, hydrated mass, which is soluble in hot water to a red solution.6... 

More complex salts are also known belonging to the series. For instance, if a solution of nitro-pentammino-cobaltic chloride be treated with an aqueous solution of sodium cobaltic nitrite, Na3Co(N02)6, a yellowish-brown crystalline precipitate of nitro-pentammino-cobaltic cobalti-nitrite, [Co(NH3)5(N02)]3[Co(N02)6]2, is formed. Also the corresponding ferrocyanicle may be prepared by treating nitro-pentammino-salts with potassium ferrocyanide. The compound obtained is a reddish-yellow substance of composition [Co(NH3)5(NO,)], [Fe(CN )6].6H20. 

Erdmann,1 in 1866, prepared the first member of this series, namely, ammonium tetranitrito-diammino-cobaltate, [Co(NH3)2(N02)4] NH4. The salt is sometimes referred to as Erdmann s salt on that account. Later, Gibbs prepared other salts of the same type, and showed that in these salts the cobalt atom, united with ammonia and acidic radicles, forms a negative radicle.2 Werner then showed that these salts form the connecting link between the neutral un-ionised complex triacido-triammino-eobalt compounds and the double salt, such as potassium eobalti-nitrite. Thus, by replacement of ammonia molecules by acid radicles a transition takes place from trinitrito-triammino - cobalt to potassium tetranitrito - diammino - cobaltate, [Co(NH3)2(N02)4]K, then to potassium pentamtrito-ammino-eobalfate. [Co(NH3)(N02)5]K, and finally to hexanitrito-cobaltate, [Co(N02)e]Iv3. Tetra-acido-diammino-cobaltates are therefore the salts of the acid tetra-acido-diammino-cobaltic acid, [Co(NH3)2R4]H. 

The best known of these compounds is potassium cobalti-nitrite, [Co(N02)6]K3.1 This salt was originally regarded as a double salt of cobaltic nitrite with potassium nitrite, and represented by the formula Co(NQ2)3.3KNOa. Such a formula, however, does not represent the reactions of the substance, as the nitrite radicle is held firmly, and nitrous aeid is not liberated when the compound is treated with cold dilute acids, as it would be if it were a double salt as the formula indicates. Molecular conductivity measurements also indicate that it is a complex salt comparable with the metal-ammines. Many compounds of cobalt of this type are known. They may be regarded as the salts of the complex acid hexanitrito-cobaltic acid, [Co (N02)6]H3. 

Cobalt Nitrite Complexes. When KNOz is added in excess to a soln of Co(NOa)2,acidified with AcOH, a yel ppt of potassium hexa-nitrocobaltiate (potassium cobaltinitrite),... 

O. L. Erdmann reported potassium cobaltous tetranitrite, K2Co(N02)4, or 6K0H.3Co3(N02)2, to be separated as a yellow crystalline powder when soln. of cobaltous chloride and an excess of potassium nitrite are mixed. No oxygen is absorbed from the air during its formation, and O. L. Erdmann, and S. P. Sadtler used an atm. of carbon dioxide. The salt was also prepared by A. Stromeyer, and C. D. Braun. The salt is insoluble in cold water, but soluble in hot water, forming a red soln. It forms a violet soln. if potassium acetate is present, containing cobaltous salts. The salt decomposes when heated. C. D. Braun said that cobaltic hydroxide is precipitated when the soln. is boiled with potash-lye. 0. L. Erdmann said that the cobalt is not contained in the salts as a base in the... 

Cobalt yields an interesting series of double nitrites, the most important member of which is Fischer s salt or potassium cobalti-nitrite, K3Co(N02)6. H20. Rhodium shares this property to a considerable extent, and the potassium salt. K3Rh(N02)6, may be used in an analogous manner to Fischer s salt, namely, in the preparation of pure rhodium, and also for the quantitative estimation of that metal. 

Potassium Cobalti-nitrite, K3Co(N02)6. H20, is the most familiar example of this type. It is also known as cobalt yellow and Fischer s salt in honour of its discoverer.1. It is readily prepared by adding potassium nitrite to an aqueous solution of a soluble cobalt salt acidified with acetic acid. It results in a very pure condition when cobalt carbonate is suspended in an aqueous solution containing an equivalent amount of potassium carbonate or nitrite, and treated with nitrous fumes (resulting from the action of nitric acid upon arsenious oxide) until it has suffered complete decomposition.2 The amount of combined water varies from 0 to 4 molecules according to circumstances. 

Potassium nitrite yields a yellow precipitate of potassium cobalti-nitrite, K3Co(N02)8, when added to a solution of a cobalt salt containing free acetic acid (see p. 60). 

Name of Complex Salt Hexammine cobaltic chloride Chloropentammine cobaltic chloride Dichlorotetrammine cobaltic chloride Trichlorotriammine cobaltic chloride Potassium tetranitrodiarnmine cobaltiate Potassium cobalti-nitrite... 

Addition of excess potassium nitrite acidified with ethanoic acid gives a precipitate of the potassium hexanitro-cobaltate(lll), K3[Co(N02)6] (P. 403). 

Evaporation by heating a filtrate from precipitation of potassium cobaltinitrite caused it to turn purple and explode violently [1]. This was attributed to interaction of nitrite, nitrate, acetic acid and residual cobalt with formation of fulminic or methylnitrolic acids or their cobalt salts, all of which are explosive [2], Mixtures containing nitrates, nitrites and organic materials are potentially dangerous, especially in presence of acidic materials and heavy metals. A later publication confirms the suggestion of formation of nitro- or nitrito-cobaltate(III) [3],... 

Fischer polypeptide synthesis org chem A synthesis of peptides in which a-amino acids or those peptides with a free amino group react with acid halides of a-haloacids, followed by amination with ammonia. fish-ar pal-e pep,tTd. sin tha sas ) Fischer projection orgchem) A method for representing the spatial arrangement of groups around chiral carbon atoms the four bonds to the chiral carbon are represented by a cross, with the assumption that the horizontal bonds project toward the viewer and the vertical bonds away from the viewer fish-ar pra.jek-shon) Fischer s salt See cobalt potassium nitrite. fish-3rz solt)... 

Addition of potassium nitrite, KNO2 to a solution of cobalt(lI) chloride yields yellow crystalline potassium hexanitrocobaltate(lIl), K3Co(N02)e. 

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