506-64-9 silver cyanide

Note.—Silver cyanide in these circumstances gives the isoCyanide, CH,NC. 

REACTIONS AND IDENTIFICATION 325 drop. JNote that the white precipitate of silver salts turns black (showing the presence of silver cyanide). Now add an excess of mercurous nitrate the black precipitate redissolves, but the silver halide remains undissolved. 

Many silver compounds are unstable to light, and are thus shipped ia brown glass or opaque plastic bottles. Silver compounds that are oxidants, eg, silver nitrate and iodate, must be so identified according to U.S. Department of Transportation (DOT) regulations. Compounds such as silver cyanide, which is toxic owiag to its cyanide content, must carry a poison label. However, most silver compounds are essentially nontoxic. 

Silver Cyanide. Silver cyanide, AgCN, forms as a precipitate when stoichiometric quantities of silver nitrate and a soluble cyanide are mixed. Sdver(I) ion readily forms soluble complexes, ie, Ag(CN) 2 01 Ag(CN) 2> die presence of excess cyanide ion. 

Cyanide Complexes. Insoluble silver cyanide, AgCN, is readily dissolved in an excess of alkah cyanide. The predominant silver species present in such solutions is Ag(CN) 2) with some Ag(CN) 3 and Ag(CN) 4. Virtually all silver salts, including the insoluble silver sulfide, dissolve in the presence of excess cyanide because the dissociation constant for the Ag(CN) 2 complex is only 4 x 10 (see Cyanides). 

Silver compounds having anions that are inherently toxic, eg, silver arsenate and silver cyanide, can cause adverse health effects. The reported rat oral LD values for silver nitrate, silver arsenate [13510-44-6] and silver cyanide are 500—800 (29), 200—400 (29), and 123 mg/kg (30), respectively. Silver compounds or complexes ia which the silver ion is not biologically available, eg, silver sulfide and silver thiosulfate complexes, are considered to be without adverse health effects and essentially nontoxic. 

Electroplating. Most silver-plating baths employ alkaline solutions of silver cyanide. The silver cyanide complexes that are obtained in a very low concentration of free silver ion in solution produce a much firmer deposit of silver during electroplating than solutions that contain higher concentrations. An excess of cyanide beyond that needed to form the Ag(CN)2 complex is employed to control the concentration. The silver is added to the solution either directly as silver cyanide or by oxidation of a silver-rod electrode. Plating baths frequently contain 40—140 g/L of silver cyanide... 

Typical equipment made from tantalum includes heat exchangers, reaction vessels liners, thermowells, and heating elements or heat shields for high temperature vacuum sintering furnaces. Tantalum fabricated parts are found in the manufacturing of pharmaceuticals, explosives, insecticides, dyes, acidic baskets for silver cyanide barrel platers, and in hydrochloric and hydrobromic acid condensers. 

The metal-plating baths used are acidic copper sulfate and alkaline silver cyanide. Acid contamination ia the alkaline silver cyanide bath will release extremely poisonous hydrogen cyanide gas. Eor this reason, the two plating setups should be isolated from each other. Both plating baths should be weU... 

Silver-plating bath compositions are somewhat variable a typical composition contains 36 g silver cyanide, 60 g potassium cyanide, 45 g potassium carbonate, and 1000 mL distilled water. A pure silver anode is required (179). 

The polysulfide mbbers are capable of beiag electroplated by a special technique. Either copper or silver can be used, but the alkaline silver cyanide plating system gives more rehable results. 

Silver cyanide [506-64-9] M 133.9, m dec at 320 , d 3.95. POISONOUS white or grayish white powder. Stir thoroughly with H2O, filter, wash well with EtOH and dry in air in the dark. It is very insoluble in H2O (0.000023g in lOOmL H2O) but is soluble in HCN or aqueous KCN to form the soluble Ag(CN) complex. [Chem Ber 72 299 I939 J Am Chem Soc 52 184 1930.]... 

Cyanide Copper cyanide Nickel cyanide Potassium cyanide Silver cyanide Sodium cyanide Zinc cyanide... 

With alkali cyanides, a reaction via a SN2-mechanism takes place the alkyl halide is attacked by cyanide with the more nucleophilic carbon center rather than the nitrogen center, and the alkylnitrile is formed. In contrast, with silver cyanide the reaction proceeds by a SnI-mechanism, and an isonitrile is formed, since the carbenium intermediate reacts preferentially with the more electronegative center of the cyanide—i.e. the nitrogen (Kornblum s rule, HSAB concept). ... 

Hydrocyanic acid may be approximately estimated by dissolving 1 gram of oil in 5 c.c. of alcohol, and adding 50 c.c. of water. Then add ammonio-silver nitrate solution and shake well. Acidify slightly with nitric acid, and collect, wash, and dry the silver cyanide precipitated. Ignite and weigh the silver, 4 parts of which correspond to practically 1 of hydrocyanic acid. 

Cyan-saure, /. cyanic acid cyano acid, -schlamm, m. cyanide sludge, -senf l, n. cyanomustard oil. -silber, n. silver cyanide. -stickstoS, m. cyanonitride. -toluol, n. cyanotoluene. 

Silber-weisfi, n. silver white, -wismutglanz, m. matildite. -zyanid, n. silver cyanide. 

A soluble cyanide added to silver nitrate solution precipitates silver cyanide as an ionic compound ... 

Silver cyanide, reaction with alkyl halides in synthesis of iso-cyamdes, 46, 77... 

Allyl cyanide has been found in oil of mustard 1 and has been prepared from allyl chloride and potassium cyanide,2 allyl bromide and potassium cyanide,3 allyl iodide and potassium cyanide4 and silver cyanide.5 The method described in the procedure is essentially that of Bruylants, who has shown that the yields are much better when dry cuprous cyanide is treated with allyl bromide.6... 

With the salts of certain weak acids, such as carbonic, sulphurous, and nitrous acids, an additional factor contributing to the increased solubility is the actual disappearance of the acid from solution either spontaneously, or on gentle warming. An explanation is thus provided for the well-known solubility of the sparingly soluble sulphites, carbonates, oxalates, phosphates(V), arsenites(III), arsenates(V), cyanides (with the exception of silver cyanide, which is actually a salt of the strong acid H[Ag(CN)2]), fluorides, acetates, and salts of other organic acids in strong acids. 

When potassium cyanide solution is added to a solution of silver nitrate, a white precipitate of silver cyanide is first formed because the solubility product of silver cyanide ... 

When the above reaction is complete, further addition of silver nitrate solution yields the insoluble silver cyanoargentate (sometimes termed insoluble silver cyanide) the end point of the reaction is therefore indicated by the formation of a permanent precipitate or turbidity. 

The only difficulty in obtaining a sharp end point lies in the fact that silver cyanide, precipitated by local excess concentration of silver ion somewhat prior to the equivalence point, is very slow to re-dissolve and the titration is time-consuming. In the Deniges modification, iodide ion (usually as KI, ca 0.01 M) is used as the indicator and aqueous ammonia (ca 0.2M) is introduced to dissolve the silver cyanide. 

Discussion. The theory of the titration of cyanides with silver nitrate solution has been given in Section 10.44. All silver salts except the sulphide are readily soluble in excess of a solution of an alkali cyanide, hence chloride, bromide, and iodide do not interfere. The only difficulty in obtaining a sharp end point lies in the fact that silver cyanide is often precipitated in a curdy form which does not readily re-dissolve, and, moreover, the end point is not easy to detect with accuracy. 

Current-voltage curve 594 Cyanide, D. of as silver cyanide, (g) 48l with silver nitrate, (ti) 358 titration with silver nitrate, 309, 358 Cyclohexane, D. of (ir) 756 Cyclohexane-1,2-dione dioxime see Nioxime... 

An analogous regioselective effect of silver ions on an addition reaction of arene-diazonium ions was found by Ignasiak et al. (1975) with cyanide salts. Potassium cyanide yields diazocyanides (Ar— N2 — C = N see Sec. 6.6), i.e., C-coupling products, but with silver cyanide - albeit in low yield (7-9%) - diazoisocyanides (Ar—N2 — N = C) are formed (a better synthesis of diazoisocyanides is described in Sec. 6.4). 

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