Cobalt ferrocyanide

A further method for the determination of caesium isotopes in saline waters [60] is based on the high selectivity of ammonium cobalt ferrocyanide for caesium. The sample (100-500 ml) is made 1 M in hydrochloric acid and 0.5 M in hydrofluoric acid, then stirred for 5-10 min with 100 mg of the ferrocyanide. When the material has settled, it is collected on a filter (pore size 0.45 im), washed with water, drained dried under an infrared lamp, covered with plastic film and / -counted for 137caesium. If 131caesium is also present, the y-spectrometric method of Yamamoto [61] must be used. Caesium can be determined at levels down to 10 pCi/1. 

The latter statement refers to concurrent work by A. Bilewicz et al. [4] who studied the sorption of Zr, Hf, Th, and Rf on cobalt ferrocyanide surfaces. These ferrocyanides are known to be selective sorbents for heavy univalent cations such as Fr+, Cs+, and Rb+. However, some ferrocyanides such as Co ferrocyanide have been found to exhibit also particularly high affinities for tetravalent elements such as Zr4+, Hf4+, and Th4+ involving the formation of a new ferrocyanide phase between the 4+ cation and the Fe(CN)4 anion. 

Cobalt ferrocyanide, Co2Fe(CN)6.7H20,9 is obtained by neutralising the free acid with cobalt hydroxide. It is less stable than the corresponding nickel salt. It is green in colour oxidised by chlorine water to ferricyanide and by bromine water to hydrated cobaltic oxide.10... 

Adsorbents have been widely used to collect dissolved Cs in both fresh and seawater. Ferrocyanide compounds are known as specific adsorbents for cesium (Krylov et al., 1973 Folsom et al., 1975 Mann and Casso, 1984) and are used in two forms, granular or impregnated on fiber. Milham and Kantelo (1984) used a granular form of potassium cobalt ferrocyanide (KCFC) to collect Cs in the Savan-... 

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. 

The yield of enriched 61Cr is, however, only about 15% of the total slCr produced, and this decreases appreciably with increase in the bombardment time. Under similar conditions, both potassium cobalti-cyanide and ferrocyanide show considerable enrichment of cobalt-60 andiron-55 and -59 although the yields are also relatively low (about 10 and 30% respectively). 

Arthur Adamson If I may, I would like to mention a reaction that I think is an example of substitution which paves the way for a redox reaction, and yet is not a case of the charge following the oxidant into the coordination sphere. This is the reaction of ferrocyanide with cobaltous EDTA. 

The final product is ferrocyanide and cobaltic EDTA, but this goes through an intermediate which can be isolated, and which is an adduct of these twro. Dr. Wilkins tried this system out in his rapid flow rate system and found a rate of association which was about right for substitution rates on a cobaltous ion. So this seemed to be a case where perhaps the nitrogen end of a cyanide was able to coordinate into a cobaltous complex, with either concomitant cr subsequent charge transfer. Yet no transfer of ligand occurs in the overall reaction. 

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. 

TiOz coated with potassium ferrocyanide proved to be an effective catalyst for the reduction of C02 to formic acid and formaldehyde.169 A very stable and reproducible catalytic system was prepared by immobilizing Ni2+ and Ru2+ complexes into Nation membrane, which was used for the selective reduction of C02 to formic acid.170 Formic acid was again formed when Zn and Co phthalocyanines were adsorbed onto a Nation membrane on irradiation with visible light in acidic aqueous solution containing triethanolamine as a hole scavenger. Cobalt comns (B i2) acting as homogeneous catalysts in acetonitrile-methanol solutions induced the formation of formic acid and CO.172... 

C. Add 1 mL of a 1 100 aqueous solution and 2 mL of a 1 50 solution of potassium ferrocyanide to 2 mL of cobaltous chloride TS. An emerald green color develops immediately. Assay Not less than 98.0% of C9H19N07, calculated on the anhydrous basis. 

Kinetics.- Kinetic tuns were carried out in the thermostated cell compartment of a Hitachi 150-20 UV-visible spectrophotometer. The cell temperature was kept at 298.2 0.1 K. The kinetics were followed at 420 nm. The cobalt(in) complex concentration was always 5 10" mol dm". All mns employed an excess of ferrocyanide. Na(H2edta) had to be added to prevent precipitation of C03[Fe(CN)6]2- The pH was kept constant at 5.7 by using the appropriate acetic/acetate buffer. The ionic strength was fixed at 0.5 mol dm by adding the adequate quantity of sodium perchlorate to the working medium in each case. 

The carbonates, sulphates, and borates are decomposed. The sulphides of the alkalies and alkaline earths are decomposed while the sulphides of arsenic, antimony, molybdenum, zinc, cadmium, tin, iron, lead, copper, mercury, and palladium are not attacked. Cobalt sulphate is not attacked, while the sulphates of the alkalies and alkaline earths are attacked and dissolved. Alkali tungstates, ammonium arsenite and arsenate, copper arsenite, ammonium magnesium arsenate, ammonium molybdate and vanadate, potassium cyanide and ferrocyanide are decomposed. Paraffin is not attacked shellac, gum arabic, gum tragacanth, copal, etc., are decomposed. Celluloid is slowly attacked. Silk paper, gun cotton, gelatin, parchment are dissolved. M. Meslans 22 has studied the esterification of alcohol by hydrofluoric acid. 

For this the easiest method is to use potassium ferrocyanide and sponge or spray it with a dilute solution of iron sulphate or use copper sulphate and sponge or spray with ammonium hydrate. If we use acetate of cobalt—then this when heated gives a very similar result. 

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