Potassium cyanide

“ We find x = 5E−7 mole, or approximately 0.03 milligram potassium cyanide (cyanide-ion) per liter. This minute quantity of free cyanide, if not originally present in the solution used, would be formed by the liberation of potassium cyanide from the complex (according to KAg (CN) 2 + KCl → AgCl + 2 KCN) as soon as 2.5E−7 mole, or 0.036 milligram, of silver chloride per liter have been formed, a quantity too small to be perceptible. ”

“ Animal matters always contain more carbon than is necessary for the formation of cyanogen by combining with the nitrogen also present. Consequently, when such substances are heated with pearlash, the excess of carbon reduces a portion of the carbonate to the metallic state, and this potassium combines with the cyanogen to produce potassium cyanide. The manufacture of yellow prussiate of potash may be conveniently divided into three stages: (1) The production of the molten mass technically known as “metal” ”

“ Skey, for the purpose of ascertaining the value of cyanide of potassium as a preventive of the flouring of mercury iised for the extraction of gold, shows that cyanide of potassium does certainly prevent the sickening and flouring of mercury, or its tarnishing and granulation; but as cyanogen appears capable of dissolving metallic mercury, and is certain to be liberated from cyanide of potassium by carbonic acid, always present, it is questionable if cyanide of potassium could ever be profitably substituted for sodium as a preventive to the flouring of mercury. ”

“ It is scarcely safe to recommend the handling of cyanide of potassium, in any form whatever, to our young readers, as it is one of the most terrible of poisons, and works much mischief and suffering by merely coming in contact with a slight cut on the finger. ”

“ J.C.S., 1907, i. p. 299) , or by the addition of a concentrated solution of potassium cyanide to one of copper sulphate, the mixed solutions being then heated. It also occurs in blast-furnace gases. When cyanogen is prepared by heating mercuric cyanide, a residue known as para-cyanogen, (CN) x, is left; this is to be regarded as a polymer of cyanogen. It is a brownish amorphous solid, which is insoluble in water. Cyanogen is a colourless gas, possessing a peculiar characteristic smell, and is very poisonous. It burns with a purple flame, forming carbon dioxide and nitrogen ”

“ An excellent reducing agent for single coins, the characters of which are rendered illegible by a layer of silver chloride, is molten potassium cyanide, or a mixture of this substance with sodium or potassium carbonate. ”

“ The salts of cyanic acid are known as the cyanates, the two most important being potassium cyanate (KOCN) and ammonium cyanate (NH4OCN) . Potassium cyanate may be prepared by heating potassium cyanide with an oxidizing agent, or by heating potassium ferrocyanide with manganese dioxide, potassium carbonate or potassium dichromate (J. v. Liebig, Ann., 1841, 38, p. 108; C. Lea, Jahresb., 1861, p. 789; L. Gattermann, Ber., 1890, 23, p. 1224) , the fused mass being extracted with boiling alcohol. It crystallizes in flat plates and is readily soluble in cold water. ”

“ The symbols [H+] , [CN−] and [HCN] denote the final concentrations for the condition of equilibrium, indicated in the equations on p. 180; in such a mixture [H+] is not equal to [CN−] , as it is in pure solutions of hydrocyanic acid in water. [CN−] , representing the total concentration of the cyanide-ion, is very much larger than [H+] , since the salt, potassium cyanide, produces the cyanide-ion in large concentrations. ”

“ Phosphate of soda, 5 parts, and caustic potash, 3 parts, and in 250 parts of water, gold chloride, 1 part, and potassium cyanide, 16 parts. Mix both {577} solutions well and cause the mixture to boil, whereupon the brass articles to be gilded are immersed. The gold in the mixture can be utilized almost entirely. When the solution does not gild well any more a little potassium cyanide is added, and it is used for pre-gilding the articles, which can then be gilded again in a fresh solution. This solution is very weak. ”

“ Thus, for instance, in the blast furnace a considerable quantity of cyanogen compounds are formed. This takes place because the nitrogen of the air blast comes into contact with incandescent carbon and various alkaline matters contained in the foreign matter of the ores. A considerable quantity of potassium cyanide is formed when wood charcoal is employed for iron smelting, as its ash is rich in potash. ”

“ On the other hand, as much silver nitrate is required to give the yellow turbidity due to silver iodide as would be required if no zinc were present.
Unfortunately the difference in the two titrations does not depend merely on the quantity of zinc present; as it is also influenced by the extent of dilution, the degree of alkalinity of the solution, and the quantity of cyanide present. In an experiment with .055 gram of zinc sulphate and .1 gram of potassium cyanide the difference in the two finishing points was only .1 c.c. ”

“ It may be well here, as a caution, to remark that the analyst must not commit the unpardonable error of first producing a cyanide by reagents acting on animal matters, and then detecting as a poison the cyanide thus manufactured. If, for example, a healthy liver is carbonised by nitric acid, saturated with potash, and then burnt up, cyanide of potassium is always one of the products ”

“ The potassium-cyanide process may be used with all small iron objects. For larger ones molten potassium rhodanide is recommended. This converts the iron oxide into iron sulphide that is easily washed off and leaves the surface of a fine black color.
Old coins may be cleansed by first immersing them in strong nitric acid and then washing them in clean water. Wipe them dry before putting away.
To Clean Old Medals.—Immerse in lemon juice until the coating of oxide has completely disappeared; 24 hours is generally sufficient, but a longer time is not harmful. ”

“ The potassium cyanide solution is standardized by dissolving 0.5 gramme of pure copper in 5 cc. of nitric acid, diluting, adding 10 cc. of ammonia, and titrating exactly as described above.
When potassium iodide is added to a solution of cupric acetate, the reaction Cu (C2H3O2) 2 + 2KI = CuI + 2K (C2H3O2) + I takes place; that is, for each atom of copper one atom of iodine is liberated. If a solution of sodium thiosulphate (hyposulphite) is added to this solution, hydriodic acid, sodium iodide and tetrathionate are formed ”

“ The cyanide liked the gold better than the potassium, but it has the bad taste to prefer zinc even to gold. It releases the gold and flies to the embrace of the zinc. The gold, suddenly deserted of the friendship of the cyanide, powders down to the bottom of the tank, in absolutely pure form, ready to be melted down into bars. By other processes, which I won't bother you by describing now, the zinc is released from the cyanide, and the cyanide is led to its old friend the potassium, ready to begin work anew. ”

“ The diazo cyanides, C6H5N2·CN, and carboxylic acids, C6H5·N2·COOH, may also be considered as mixed azo derivatives. Diazobenzenecyanide, C6H5N2·CN, is an unstable oil, formed when potassium cyanide is added to a solution of a diazonium salt. Phenyl-azo-carboxylic acid, C6H5·N2·COOH, is obtained in the form of its potassium salt when phenylsemicarbazide is oxidized with potassium permanganate in alkaline solution (J. Thiele, Ber., 1895, 28, p. 2600) . It crystallizes in orange-red needles and is decomposed by water. ”

“ Assay of commercial cyanide of potassium.—Break off 20 or 30 grams of the cyanide in clean fresh pieces, weigh accurately to the nearest centigram. Dissolve in water containing a little sodium hydroxide; transfer to a 2-litre flask: dilute to 2 litres; add a few grams of white lead; shake up and allow to settle. Run 50 c.c. of the clear liquor from a burette into an 8 oz. flask; add 2 or 3 c.c. of soda solution and 3 drops of potassium iodide. Titrate with the standard solution of silver nitrate. The percentage may be calculated by multiplying the number of c.c. ”

“ Richard Brunquell passes ammonia through tubes filled with charcoal, and heated to redness so as to form cyanide of ammonium, which is converted into the ferrocyanide of potassium by contact with potash solution and suitable iron compounds. Ferrocyanide of potassium is in large beautiful transparent four-sided tabular crystals, of a lemon-yellow color, soluble in four parts of cold and two of boiling water, insoluble in alcohol. Exposed to heat it loses three eq. of water, and becomes anhydrous; at a high temperature it yields cyanide of potassium, carbide of iron, and various gases. ”

“ When cyanide of potassium is being used it should never be allowed to come in contact with the skin, and even a slight odor of the gas should be avoided. Should the operator have any cut or break in the skin of the hands or face it should be carefully covered with court-plaster to prevent the gas coming in contact with the flesh, or a small particle of the solid compound getting into the cut might cause death by poisoning in a few minutes’ time. ”

“ Carbonic oxide or not, Templeton and Miss Wainwright were asphyxiated.”
It was now Whitney's chance to air his theory.
“I have always inclined toward the cyanide-of-potassium theory, either that it was administered in a drink or perhaps injected by a needle,” he said. “One of the chemists has reported that there was a possibility of slight traces of cyanide in the mouths.”
“If it had been cyanide,” replied Craig, looking reflectively at the two jars before him on the table, “these blood specimens would be blue in colour and clotted. But they are not. ”

“ Cyanide of Potassium (Vol. ix., p. 230.) .—I have for a long time been in the habit of using a solution of the above-named substance for fixing collodion positives, because the reduced silver has a much whiter appearance when thus fixed, than when the hyposulphite of soda is used for the same purpose; but I cannot quite agree with Mr. Hockin that it is equally applicable to negatives, though in many cases it will do very well. I find the reduced metal is more pervious to light when fixed with the cyanide solution, particularly in weak negatives. ”

“ The real cause of this rapid decomposability of the plasm, and of the accompanying formation of carbonic acid, is found in the cyanogen, a remarkable body composed of an atom of carbon and an atom of nitrogen, which, in conjunction with potassium, forms the well-known and very virulent poison, cyanide of potassium. The non-nitrogenous decomposition-products of the dead and the living albumin agree in the main, but their nitrogenous products are totally different. ”

“ When the sulphuric acid comes in contact with the cyanide of potassium the result is the formation of sulphate of potash, which remains in the jar, and the hydrocyanic acid is liberated and {419} escapes into the air. The chemical action is so violent as to cause a sputtering, and frequently particles of the acid are thrown over the sides of the jar ”

“ Where a large number of results are wanted quickly it is a very convenient method. The iodide process is very satisfactory when worked under the proper conditions.
CYANIDE METHOD.
The process is based upon the facts— (1) that when ammonia is added in excess to a solution containing cupric salts, ammoniacal copper compounds are formed which give to the solution a deep blue colour; and (2) that when potassic cyanide is added in sufficient quantity to such a solution the colour is removed, double cyanides of copper and potassium or ammonium being formed. ”

“ Hydrocyanic acid gas should not be used in closely built apartments with single walls between, as more or less of the gas will penetrate a brick wall. An inexperienced person should never use cyanide of potassium for any purpose, and if it be found practicable to treat buildings in general for the extermination of insects, the work should be done only under the direction of competent officials. ”

“ Hydrocyanic or prussic acid, which consists of 1 atom of cyanogen = 26, + 1 of hydrogen = 1, is prepared by distilling the mercurial bi-cyanide in a glass retort with the saturating quantity of dilute muriatic acid. Prussic acid may also be obtained by precipitating the mercury by sulphuretted hydrogen gas from the solution of its cyanide; as also by distilling the ferrocyanide of potassium along with dilute sulphuric acid. Prussic acid is a very volatile light fluid, eminently poisonous, and is spontaneously decomposed by keeping, especially when somewhat concentrated. ”

“ Expose well-dried and powdered ferrocyanide of potassium to a moderate red heat, in a close vessel; when cold, powder the fused mass, place it in a funnel, moisten it with a little alcohol, and wash it with cold water; evaporate the solution thus formed to dryness, expose it to a dull red heat in a porcelain dish, cool, powder, and digest it in boiling rectified spirit; as the spirit cools, crystals of cyanide of potassium, nearly pure, will be deposited. The alcohol employed in both this and the preceding process may be recovered by distillation from calcined sulphate of iron. ”

“ For making these, some sulpho-cyanide of potassium is poured into a solution of nitrate acid on mercury, which forms a precipitate of sulpho-cyanide of mercury. This is a white, combustible powder, which after passing through a filter, should be transformed into a stiff pulp by means of water containing a solution of gum. The pulp is afterwards mixed with a small quantity of nitrate of potash, and fashioned into cones or cylinders of about an inch and a quarter in length, which should be thoroughly dried. ”