Potassium barium ferrocyanide

Potassium barium ferrocyanide, K2BaFe(CN)6.3lT20, results as a... 

The formula of potassium arsenate is K3ASO4. The formula of potassium ferrocyanide [systematically called potassium hexacyanoferrate(II)] is K4Fe(CN)6. Write the formulas of (a) calcium arsenate, (b) iron(III) arsenate, (c) barium ferrocyanide, (d) aluminum ferrocyanide. 

Ammonium cyanide may be prepared in solution by passing hydrogen cyanide into aqueous ammonia at low temperatures. It may also be prepared from barium cyanide and ammonium sulfate, or calcium cyanide with ammonium carbonate. It may be prepared in the dry state by gentiy heating a mixture of potassium cyanide or ferrocyanide and ammonium chloride, and condensing the vapor in a cooled receiver. Ammonium cyanide is soluble in water or alcohol. The vapor above soHd NH CN contains free NH and HCN, a very toxic mixture. 

The hematite with adsorbed Co-57 or Sb-119 along with the solution was subjected to emission Mossbauer measurement at 24 1°C with the experimental setup shown in Figure 2. The absorber, Fe-57-enriched potassium ferrocyanide (0.5 mg Fe-57/cm2) or barium stannate (0.9 mg Sn-119/cm2), was driven by a Hanger 700-series Mossbauer spectrometer connected to a Tracor-Northern TN-7200 multi-channel analyzer. The Mosssbauer gamma-rays of Co-57 and Sb-119 were detected respectively with a Kr(+3% carbon dioxide)-filled proportional counter and with a 2 mm-thick Nal(Tl) scintillation counter through 65 pm-thick Pd critical absorber for Sn K X-rays. The integral errors in the relative velocity were estimated to be of the order of 0.05 mm/s by repeated calibration measurements using standard absorbers. 

Sulphates, Copper, and Alkalies. — Boil for a few minutes a solution of 5 gm. of ferrous chloride in 10 cc. of water and 5 cc. of nitric acid (sp. gr. 1.3), dilute to 120 cc., add 20 cc. of ammonia water, and filter evaporate 50 cc. of the filtrate and ignite the residue. The weight of the latter should not exceed 0.001 gm. Slightly acidulate 20 cc. of the filtrate with hydrochloric acid and add barium nitrate solution. No change should appear. 20 cc. of the filtrate acidified with acetic acid should show no change upon addition of potassium ferrocyanide solution. 

Sulphates. — Dissolve 1 gm. of potassium ferrocyanide in 20 cc. of water, and add 1 cc. of hydrochloric acid followed by barium chloride solution. No immediate turbidity should ensue. 

Hydrogen nitroso ferricyanide or nitroprussic acid, H2[Fe(CN)5NOJ, is obtained by decomposition of the silver salt with hydrochloric acid or by the action of dilute sulphuric acid upon the barium salt. It is also formed when nitric oxide is bubbled through an acidified solution of potassium ferrocyanide.4 The reaction proceeds in two stages, namely, (a) oxidation to the ferricyanide, and (b) substitution of the cyanogen radicle by NO —... 

Vanadium compounds (vanadic acid and vanadium chloride) have been proposed as substitutes for copper sulphide, but without much practical success. Potassium ferrocyanide and ferricyanide are also used to a certain extent. A mixture of these salts with aniline salt and potassium chlorate is printed, and the goods aged. The probable action is that the ferricyanide oxidises the aniline, and is continually regenerated from the ferrocyanide formed by the chloric acid present. Thus these salts play the part of oxygen carriers in a similar manner to the copper and vanadium compounds. In the opinion of technologists, the hlack produced by this process differs somewhat in its properties from that obtained with copper, but this may be ascribed to the presence of prussiaii blue in the former. In place of the aniline hydrochloride and potassium chlorate, a mixture of aniline sulphate and barium chlorate has recently been employed in black-printing. 

Characters and Tests.—Blue crystalline salt, in oblique prisms, soluble in water, forming a pale blue solution which strongly reddens blue litmus. The aqueous solution gives with barium chloride a white precipitate (barium sulphate), insoluble in hydrochloric acid, showing the salt to be a sid-phate and with potassium ferrocyanide a maroon-red precipitate, indicating the presence of copper (cupric ferrocyanide). If an aqueous solution of the salt be mixed with twice its volume of chlorine water, to peroxidize any iron that may be present, and solution of ammonia be added, the precipitate (cupric hydrate) formed by the first addition of the ammonia will be dissolved by a further and sufficient addition of the alkali, and a violet blue solution (copper ammonio-sulphate) will be produced, leaving nothing un ssolved unless iron be present, in which case a reddish-brown precipitate will be left. 

---