Silver chloride cyanide

Silver chloride is readily soluble in ammonia, the bromide less readily and the iodide only slightly, forming the complex cation [Ag(NH3)2]. These halides also dissolve in potassium cyanide, forming the linear complex anion [AglCN) ] and in sodium thiosulphate forming another complex anion, [Ag(S203)2] ... 

To determine which halogen is present, take 1-2 ml. of the filtrate from the sodium fusion, and add dilute sulphuric acid until just acid to litmus. Add about 1 ml. of benzene and then about 1 ml. of chlorine water and shake. A yellowish-brown colour in the benzene indicates bromine, and a violet colour iodine. If neither colour appears, the halogen is chlorine. The result may be confirmed by testing the solubility of the silver halide (free from cyanide) in dilute ammonia solution silver chloride is readily soluble, whereas the bromide dissolves with difficulty, and the iodide not at all. 

Silver Chloride. Silver chloride, AgCl, is a white precipitate that forms when chloride ion is added to a silver nitrate solution. The order of solubility of the three silver halides is Cl" > Br" > I. Because of the formation of complexes, silver chloride is soluble in solutions containing excess chloride and in solutions of cyanide, thiosulfate, and ammonia. Silver chloride is insoluble in nitric and dilute sulfuric acid. Treatment with concentrated sulfuric acid gives silver sulfate. 

Determination of silver as chloride Discussion. The theory of the process is given under Chloride (Section 11.57). Lead, copper(I), palladium)II), mercury)I), and thallium)I) ions interfere, as do cyanides and thiosulphates. If a mercury(I) [or copper(I) or thallium(I)] salt is present, it must be oxidised with concentrated nitric acid before the precipitation of silver this process also destroys cyanides and thiosulphates. If lead is present, the solution must be diluted so that it contains not more than 0.25 g of the substance in 200 mL, and the hydrochloric acid must be added very slowly. Compounds of bismuth and antimony that hydrolyse in the dilute acid medium used for the complete precipitation of silver must be absent. For possible errors in the weight of silver chloride due to the action of light, see Section 11.57. 

Silver bromide Silver chloride Silver perchlorate Silver cyanide Silver fluoride Silver iodide Silver permar>gate Silver nitrate Silver carbonate Silver oxide Silver sulphate Silver sulphide Silver phosphate... 

Kiss An obsolete process for extracting silver from its ores. The ores were roasted with sodium chloride, producing silver chloride, and this was leached out with a solution of calcium thiosulfate. The process was replaced by the cyanide process. 

The redispersion of a sol which has been precipitated by the addition of an electrolyte may also occasionally be effected by the removal of the precipitating agent through washing thus certain precipitates such as silver chloride, zinc sulphide and copper ferro-cyanide are readily redispersed in water where the precipitating salts are removed by thorough agitation and filtration. 

Silver is widely distributed throughout the world. It rarely occurs in native form, but is found in ore bodies as silver chloride, or more frequently, as simple and complex sulfides. In former years, simple silver and gold-silver ores were processed by amalgamation or cyanidation processes, The availability of ores amenable to treatment by these means has declined. Most silver is now obtained as a byproduct or coproduct from base metal ores, particularly those of copper, lead, and zinc. Although these ores are different in mineral complexity and grade, processing is similar. 

The potential of the silver-silver chloride electrode is sensitive to traces of bromide in the solution used to deposit AgCl. The presence of 0.01 mole percent (mol %) of bromide in a KC1 electrolyte is sufficient to alter the potential of electrodes immersed in the solution by 0.1-0.2 mV.28 The potentials are not greatly affected by traces of iodide or cyanide. Light of ordinary intensities does not have a marked effect on the potential of the electrodes, but exposure to direct sunlight should be avoided. 

Surprisingly, when diphenyl tellurium chloride iodide is stirred with an equimolar amount of silver cyanide in chloroform, silver chloride is precipitated instead of the more insoluble silver iodide and diphenyl tellurium iodide cyanide (m.p. 142°) was isolated in almost quantitative yield1."... 

Example 24 What happens if, to a mixture which contains 0-1432 g silver chloride and 0-2348 g silver iodide, (a) ammonia and (b) potassium cyanide solution is added The final volume of the solution is 100 ml, and the concentrations of free ammonia and free potassium cyanide are 2 mol 1 and 0-05 mol "1 respectively. 

To detect silver in a mixture of lead chloride, mercury(I) chloride, and silver chloride) (Group I), the mixture is treated with 10 per cent potassium cyanide solution whereby mercury(II) cyanide, mercury, and dicyanoargentate [Ag(CN2] are formed after filtration (or centrifugation), a little of the clear filtrate is treated on a spot plate with a drop of the reagent and 2 drops nitric acid (2m). A red colouration is formed in the presence of Ag in weakly acid solution. 

Silver nitrate solution white, curdy precipitate of silver chloride, AgCl, insoluble in water and in dilute nitric acid, but soluble in dilute ammonia solution and in potassium cyanide and sodium thiosulphate solutions (see under Silver, Section III.6, reaction 1, also under Complex Ions, Section 1.33) ... 

Chloride and cyanide in the presence of each other Both silver chloride and silver cyanide are insoluble in water, but soluble in dilute ammonia solution. Three methods are available for the detection of cyanide in the presence of chloride. 

Removal of silver salts Warm the insoluble unknown or the residue from 1 (if lead salts are present) with a concentrated solution of potassium cyanide. (If it dissolves completely, only AgCl, AgBr, Agl, and AgCN are present.) Filter and reserve the residue, R, for subsequent treatment. Dilute the filtrate considerably and treat with hydrogen sulphide. Filter off any black precipitate (Ag2S), wash, dissolve in hot dilute nitric acid and add dilute hydrochloric acid. A white precipitate of silver chloride indicates the presence of silver. 

Its heat of formation from the two cyanides is 5-6 Cal.1 Addition of silver chloride to its solution precipitates silver cyanide 2... 

The relative insolubility of some of the salts of silver is in the order chloride, cyanide, thiocyanate, bromide, iodide, and sulphide. The metal is usually estimated gravimetrically as chloride, or by electrolytic deposition. It can also be weighed as chromate.1 Other gravimetric methods are reduction to metal by hypophosphorous acid,2 and by alkaline glycerol and other reagents.3... 

The silver-silver chloride electrode consists of a mounted platinum screen that has been heavily plated with silver from a cyanide bath, rinsed, aged in an acidified silver nitrate solution, rinsed, coated with a thin layer of silver chloride by anodizing in a dilute HCl solution (preferably no more than a few days before use), and kept in dilute HCl pending use. This is mounted in a glass sleeve with a small hole in the bottom to admit the cell... 

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