Sodium cyanide solution

Zinc cyanide. Solutions of the reactants are prepared by dis solving 100 g. of technical sodium cyanide (97-98 per cent. NaCN) in 125 ml. of water and 150 g. of anhydrous zinc chloride in the minimum volume of 50 per cent, alcohol (1). The sodium cyanide solution is added rapidly, with agitation, to the zinc chloride solution. The precipitated zinc cyanide is filtered off at the pump, drained well, washed with alcohol and then with ether. It is dried in a desiccator or in an air bath at 50°, and preserved in a tightly stoppered bottle. The yield is almost quantitative and the zinc cyanide has a purity of 95-98 per cent. (2). It has been stated that highly purified zinc cyanide does not react in the Adams modification of the Gattermann reaction (compare Section IV,12l). The product, prepared by the above method is, however, highly satisfactory. Commercial zinc cyanide may also be used. 

Conduct the preparation in the fume cupboard. Dissolve 250 g. of redistilled chloroacetic acid (Section 111,125) in 350 ml. of water contained in a 2 -5 litre round-bottomed flask. Warm the solution to about 50°, neutralise it by the cautious addition of 145 g. of anhydrous sodium carbonate in small portions cool the resulting solution to the laboratory temperature. Dissolve 150 g. of sodium cyanide powder (97-98 per cent. NaCN) in 375 ml. of water at 50-55°, cool to room temperature and add it to the sodium chloroacetate solution mix the solutions rapidly and cool in running water to prevent an appreciable rise in temperature. When all the sodium cyanide solution has been introduced, allow the temperature to rise when it reaches 95°, add 100 ml. of ice water and repeat the addition, if necessary, until the temperature no longer rises (1). Heat the solution on a water bath for an hour in order to complete the reaction. Cool the solution again to room temperature and slowly dis solve 120 g. of solid sodium hydroxide in it. Heat the solution on a water bath for 4 hours. Evolution of ammonia commences at 60-70° and becomes more vigorous as the temperature rises (2). Slowly add a solution of 300 g. of anhydrous calcium chloride in 900 ml. of water at 40° to the hot sodium malonate solution mix the solutions well after each addition. Allow the mixture to stand for 24 hours in order to convert the initial cheese-Uke precipitate of calcium malonate into a coarsely crystalline form. Decant the supernatant solution and wash the solid by decantation four times with 250 ml. portions of cold water. Filter at the pump. 

Suberic acid. Prepare hexamethylene dibromide from hexamethy-lene glycol (Section 111,15) according to the procedure described in Section 111,35). Convert the 1 6-dibromohexane, b.p. H4r-115°/12 mm., into hexamethylene dicyanide, b.p. 178-180°/15 mm., by refluxing it with a 20-25 per eent. excess of aqueous - alcoholic sodium cyanide solution (compare Section 111,114), distilling off the hquid under diminished... 

Chrysean (10), prepared by bubbling hydrogen sulfide through a sodium cyanide solution, was among the first described thiazoles (53-57). Other 5-aminothiazoles are also most easily prepared bv hetero-cyclization (see Chapter 11. Section II.5.A). 

A German process produces a high (99%) sodium cyanide assay by absorbing the gases from a BMA-type hydrogen cyanide reactor direcdy in sodium hydroxide solution (56). The resulting sodium cyanide solution is heated in a crystallizer to remove water, and form sodium cyanide crystals. 

Nowadays, the gold content of ores is much too low for these simple mechanical separation methods to be effective. Instead, the ore is treated with very dilute (0.01 M) sodium cyanide solution, through which air is blown. The following redox reaction takes place ... 

To a flask equipped with two dropping funnels and containing 2 liters of saturated sodium chloride solution, 50.0 gm (0.51 mole) of cuprous chloride, 2.0 gm of copper powder, and 50 ml of concentrated hydrochloric acid warmed to 75°C is added a 30% sodium cyanide solution until the pH approaches approximately 3-4. At this time 150.0 gm (2.0 mole) of propargyl chloride is added dropwise over a 4-hr period. At the same time, more of the aqueous 30 % sodium cyanide is added to keep the pH constant at 3-4. The reaction product is later steam-distilled from the catalyst solution, separated from the water, dried, and fractionally distilled to afford 96.0 gm (73 %), b.p. 60°-67°C (95 mm), n ° 1.44-1.45. This product is contaminated with propargyl cyanide and is refractionated to afford pure cyanoallene, b.p. 50°-51.5°C (50 mm), d° 1.4612, Amax 46,500 cm 1, emax 14,200 (methanol). 

Gold particles in crushed rock can be brought into solution as Au(CN)2 ion by leaching the rock with aerated sodium cyanide solution (see Exercise 15.2) the aluminosilicates remain undissolved ... 

Cyanide Method of Dissolving Gold. Put 0.01 g of gold foil into a test tube, add the calculated amount of a 0.03% sodium cyanide solution (in a fume cupboard ), and, while shaking the contents of... 

Sodium cyanide solution dissolves certain metals (I) with absorption of oxygen, e.g.. gold, silver, mercury, lead, and (2) with evolution of hydrogen, e.g.. copper, nickel, iron. zinc, aluminum, magnesium and solid sodium cyanide, when heated with certain oxides, e.g.. lead monoxide PhO. stannic oxide SnO.. yields the metal of the oxide, e.g.. lead. tin. respectively. and sodium cyanate NaCNO. Two classes of esters arc known, cyanides or nitriles, and isocyanides, isonitriles or carbylatnincs. the latter being very poisonous and of marked nauseating odor... 

In a 5-I. round-bottom flask, fitted with a mechanical stirrer and surrounded by an ice-salt bath, are placed 1500 cc. of technical formaldehyde (sp. gr. 1.078/20°) (Note 1) and 540 g. of ammonium chloride. A thermometer is placed in the liquid, which is cooled to o°. This temperature is maintained throughout the entire reaction (Note 2). Stirring is commenced (Note 3) and a solution of 490 g. of 98 per cent sodium cyanide in 850 cc. of water is dropped into the mixture of ammonium chloride and formaldehyde at such a rate (about 90 drops per minute) that at least six hours will be required for this addition. When one-half the sodium cyanide solution has been added, all of the ammonium chloride will be in solution. At this point, the addition of 380 cc. of glacial acetic acid is started at such a rate (2 to 2.5 cc. per minute) that the addition of both the acid and the remainder of the sodium cyanide solution will be completed at the same time. The methylene aminoacetonitrile begins to separate in white crystals shortly after the addition of the glacial acetic acid has commenced. After all the sodium cyanide solution and acetic acid have been added, the mixture is stirred for an hour and a half longer then the precipitate... 

When one-half the sodium cyanide solution has been added, all of the ammonium chloride will be in solution. At this point, the addition of 380 cc. of glacial acetic acid is started at such a rate (2 to 2.5 cc. per minute) that the addition of both the acid and the remainder of the sodium cyanide solution will be completed at the, same time. The methylene aminoacetonitrile begins to separate in white crystals shortly after the addition of the glacial acetic acid has commenced. After all the sodium cyanide solution and acetic acid have been added, the mixture is stirred for an hour and a half longer then the precipitate... 

Sodium Cyanide Solutions. Cover the cyanide solution with a 1 1 1 mixture by weight of sodium carbonate or calcium carbonate, clay cat litter (bentonite), and sand. Scoop this mixture into a container in the fume hood. Slowly add this slurry to a large pail containing household bleach (about 70 mL/g of cyanide). Proceed as per waste disposal procedure.4,6... 

After heating to 623 K in helium, which also effected reduction according to XAFS, treatment with sodium cyanide solution removed the Au°, and left 10% of gold as cationic Au111.54 The specific rate of carbon monoxide oxidation was constant, irrespective of the treatment with sodium cyanide, as were activation energy and orders of reaction. It appeared that the Au111 was reduced under reaction conditions, and was not an active species. 

Triphenyl Tellurium Cyanide1 20 g of a Baker CHA-541 resin are treated with aqueous sodium cyanide solution, the column is washed with ethanol/water mixtures with increasing ethanol content, and, finally, the column is covered with 95% ethanol. A solution of 0.1 g (2.5 mmol) of triphenyl telluronium chloride in 60 ml of 95% ethanol is slowly passed through the column. The column is eluted with 200 ml of ethanol, the cluate is evaporated, the oily residue is triturated with ethyl acetate, and the crystals are collected, washed with ethyl acetate, and dried under vacuum yield 0.82 g (85%) m.p. 184° (dec.). 

The sodium cyanide solution added for the reaction is as follows (enough is always charged for 100 percent DCB conversion no matter what the actual conversion is) ... 

After the sodium cyanide solution is added, the. bottle is stoppered securely, placed in a mechanical shaker, and shaken for four hours at room temperature. At the end of this time the solution is transferred to a 3-I. distilling flask and 600 cc. of concentrated hydrochloric acid (sp. gr. 1.19) is added (Note 3). 

Similar to the cyanohydrin synthesis for hydroxy acids is the Strecker synthesis of amino acids. Aldehydes and ketones are converted to a-amino cyanides by ammonia and hydrogen cyanide or by aqueous ammonium chloride and sodium cyanide solutions. Amino cyanides may also be obtained by the action of gaseous ammonia on cyanohydrins (cf. method 391). The preparation of DL-alanine (60%) is typical. "... 

Heap leaching, ie, spraying of sodium cyanide solution over roughly cmshed ores heaped on an impervious pad, has become the most economical way of recovering precious metal values from very low grade ores. Recoveries are lower, however, ca 70%, for heap leaching ca 85% for milling and cyanidization. 

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