Potassium acetate ferrocyanide

Silver carbonyl ferrocyanide, Ag3[Fe(CN)5CO], is obtained as a white curdy precipitate on addition of the potassium salt to silver nitrate solution in the presence of acetic acid.4 It rapidly darkens even when protected from the light. Insoluble in boiling acetic acid, it is slightly soluble in dilute mineral acids evolving hydrogen cyanide. Potassium hydroxide liberates silver oxide, potassium carbonyl ferrocyanide being simultaneously produced. 

Potassium Acetate Potassium Acid Sulfate Potassium Acid Tartrate Potassium Antimonate Potassium Bicarbonate Potassium Bichromate Potassium Bisulfate Potassium Bisulfite Potassium Bitartrate Potassium Borate Potassium Bromate Potassium Bromide Potassium Carbonate Potassium Chlorate Potassium Chloride Potassium Chromate Potassium Cyanide Potassium Dichromate Potassium Ferricyanide Potassium Ferrocyanide Potassium Fluoride Potassium Hexacyanoferrate (III) Potassium Hydrogen Carbonate Potassium Hydrogen Sulfate Potassium Hydrogen Sulfite Potassium Hydroxide Potassium Hypochlorite Potassium Hyposulfite Potassium lodate Potassium Iodide Potassium Manganate Potassium Nitrate Potassium Perborate Potassium Perchlorate Potassium Permanganate Potassium Peroxydisulfate Potassium Persulfate... 

Copper(ll) nitrate, being an oxidizing agent, can undergo violent reactions with readily oxidizahle substances. Reaction with acetic anhydride is violent, and heating with potassium or ammonium ferrocyanide at 220°C may cause an explosion. It can ignite paper on prolonged contact. 

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. 

Copper and Iron, — On acidifying 10 cc. of lead subacetate solution with 2 cc. of dilute acetic acid, and adding potassium ferrocyanide solution, a precipitate forms which should have a pure white color. 

The evidence for the formation of complex heteropoly-acids with tantalic acid is very comparable to that set forth in the case of niobic acid (see p. 165). Solutions of tantalates are readily hydrolysed in aqueous solution by boiling, and even more readily by the addition of mineral acids, acetic acid or succinic acid in the presence, however, of arsenious add, arsenic add, tartaric add or dtric add no precipitation of tantalic add takes place. Again, tincture of galls yields a yellow predpitate with solutions of tantalates which have been rendered feebly acid with sulphuric add this reaction does not, however, take place in the presence of ordinary tartaric add, racemic add or citric acid. Tartaric add also prevents the formation of the predpitates which are thrown down on the addition of potassium ferrocyanide or potassium ferricyanide to faintly acid solutions of tantalates, and hinders the precipitation of tantalic add from solutions in inorganic acids by the action of ammonia. In all these cases it is assumed that complex acids or their salts are produced, in consequence of which the usual reaction does not take place. 

The titration is then repeated, all but 2 c.cs. of the volume of glucose solution used in the first determination being run in at once, and the remainder in drops until the blue colour just vanishes. The end point is more easily observed when the dish is slightly tilted. Several determinations are made until concordant results are obtained. If the end point is indistinct, a dilute acetic acid solution of potassium ferrocyanide spotted on a white plate may be used as external indicator. A brown coloration is observed so long as copper is present in solution. 

Copper is tested for by digesting the minium with ammonia solution and filtering in presence of copper the filtrate is bluish and after addification with acetic acid gives the brown coloration with potassium ferrocyanide. 

Broth Samples. Clarification with Zinc Acetate-Potassium Ferrocyanide. Transfer an aliquot of filtered broth expected to contain between 5 and 15 mg. of... 

Sbberellic acid to a 50-ml. volumetric flask, add 10.0 ml. of absolute alcohol, and lute to about 40 ml. with water. Add 2.0 ml. of zinc acetate solution, followed, after 2 minutes, by 2.0 ml. of potassium ferrocyanide solution. Adjust the contents of the flask to 50 ml. with water, mix, allow the flask to stand at room temperature for 5 minutes, and filter the contents through a Whatman No. 52 filter paper. Transfer 10.0-ml. aliquots of the filtrate to each of two 100-ml. volumetric flasks and add 8.0 ml. of absolute alcohol to each. Complete die determination as described above commencing with the addition of dilute hydrochloric acid (30%) to the first (sample) flask. 

Zinc salts, in the presence of sodium acetate, yield a white precipitate with hydrogen sulfide. This precipitate, which is insoluble in acetic acid, is dissolved by 2.7 N hydrochloric acid. A similar precipitate is produced by ammonium sulfide TS in neutral or alkaline solutions. Solutions of zinc salts yield with potassium ferrocyanide TS (10%) a white precipitate that is insoluble in 2.7 N hydrochloric acid. 

There are several salts that behave in this way at atmospheric temperatures, the more important being ammonium acetate potassium bromate, carbonate, cyanide, ferricyanide, ferrocyanide, iodate, and permanganate disodium hydrogen phosphate and sodium borate and carbonate.4 In the case of potassium chlorate the points L and S appear to be practically coincident, whilst for the majority of salts the point S lies somewhere to the left of L, namely at S —that is to say, saturation occurs before the limiting concentration is reached. Generally speaking, at the ordinary temperature, concentrated solutions of salts are less corrosive than distilled water—that is, the point S lies below the level of A, exceptions being 5 ammonium sulphate, aluminium... 

Copper, Nitric Acid, etc. (Alkali Salts, Calcium). — Dilute 20 iM. of ferric chloride solution (1 1) with 100 cc. of water, fuld 25 cc. of ammonia water, and filter. On evaporating 50 cc. of the colorless filtrate and igniting the residue, the weight of the latter should not exceed 0.001 gm. On mixing 2 cc. of the filtrate with 2 cc. of concentrated sulphuric acid, and overlaying tliis mixture with 1 cc. of ferrous sulphate solution, no brown zone should form at the contact-surfaces of the two licpiids. 20 cc. of the filtrate acidulated With acetic a

potassium ferrocyanide solution. 

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. 

Testa for the Purity of Acetic Acid. By heat it escapes entirehj in vapor. Either nitrate of silver or chloride of banum being added to it, will produce no precipitate. When a thin plate of silver is digested in it, and hydrochloric acid subsequently dropped in, no precipitate is formed. Its color is nn-changM by the addition of hydrosulpburic acid, or ammonia, or by ferrocyanide of potassium added after the ammonia. The presence of sulphuric acid is indicated by a white precipitate being formed on the addition of a little peroxide of lead. 

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