Cobalt nitrite

Oxime 85 with sodium cobalt nitrite Na3Co(N02)6 forms a poorly water soluble Cobalt(III) complex CoL3 that, by contrast to 85, is relatively stable to acids. 

Triammino-cobaltic nitrite is not ionised in solution, so that in this particular ease the principal valency bonds do not show the characteristics at first laid down for them by Werner. If the substance is treated with ammonia, one, two, or even three of the nitro groups may he replaced by ammonia and the following results are obtained. The entrance of one molecule of ammonia causes the compound to become ionised, and in solution one (N02) ion may be detected. A nitro-group has therefore been expelled from the undissociated zone with production of a new compound of formula... 

Ionisation Metamerism.—Numerous examples of this type of isomerism occur in the cobalt-ammine series, such as the two metameric substances, ehloro-nitrito-tetrammino-cobaltic chloride, [Co(NH3)4Cl. NOJC1, and dichloro-tetrammino-cobaltic nitrite, [Co(NH3)4C12]N02.1... 

Nitro-pentammino-cobaltic Nitrite, [Co(NH3)5(N02)](N02)2. 2H20, is prepared by heating aquo-pentammino-eobaltic sulphate with barium nitrite, or by treating a solution of chloro-pentammino-cobaltie 1 Werner, Ber., 1907, 40, 284. 

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. 

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 Nitrites,Cobaltous Nitrite, Co(NOz)2, red crysts, mp-decomp on slight heating was first prepd in 1848 (Ref 1) on treating an aqueous suspension of Co pdr with Ag nitrite soln. Several other methods of prepn are listed in Ref 2. There are also known basic cobaltic nitrite and basic cobalto-cobaltic nitrite (Ref 2), but no cobaltic salt, Co(N02)3... 

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),... 

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. 

A. Rosenheim and I. Koppel obtained a green compound, thought to be copper cobaltic nitrite, by the action of sodium cobaltic nitrite on a cupric salt. 

S. M. Jorgensen prepared cobaltichexamminohexanitrite,l[Co(NH3)6][Co(NOa)6], as a yellow powder by mixing soln, of cobaltic hexamminochloride, and sodium cobaltic nitrite. It is almost insoluble in water and when treated with thallium sulphate gives scarlet-red thallous cobaltic hexanitrite, [Co(N0a)6]Tl3. P. Jacobson prepared cobaltic hexamminotrinitrite, [Co(NH3)6](NOa)3, by the action of solid sodium nitrite on cobaltic hexamminotrichloride. This salt was also prepared by C. Duval. E. Birk, and W. Biltz studied the mol. vol. 

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