Silver residues, purification

Silicon, higher chlorides of, 42 Silicon tetrabromide, 38, 40 Silicon tetrachloride, 44 Silicopropane, octachloro, 44 Silicotungstic acid, 129 analysis, 131 ether complex, 131 Silver, metallic, 4 Silver chloride, reduction of, 3 Silver cyanamide, 98 Silver residues, purification of, 2 Sodium amalgam, 10 Sodium amide, 74 Sodium azide, purification of, 79 Sodium azidodithiocarbonate, 82 Sodium butoxide, 88 Sodium hypochlorite (solution), 90 Sodium iodate, 168 Sodium metaperiodate, 170 Sodium paraperiodate, chlorine method, 169 persulfate method, 170 Strontium amalgam, 11 Sulfur hexafluoride, 121 Sulfuryl chloride, 114... 

The a-methoxy ester is prepared following a literature procedure 3 5 To a mixture of methyl iodide (0.3 mL) and the ene product (104 mg, 0.50 mmol) in ether (1-2 mL) is added silver(l) oxide (0.23 g). The reaction mixture is stirred for 1 day at room temperature. The suspension is filtered through a pad of Celite and the filtrate is evaporated under reduced pressure. Chromatographic purification of the residue gives the a-methoxy ester in quantitative yield (110 mg). 

An alternative method of purification is to wash the silver iodide with 250 ml. of methanol instead of benzene. The ether is evaporated, and the residue is combined with the methanol solution. The product is crystallized at—70°. Recrystallization of this crude product from methanol at —70° gives the same yields as the other method of purification. 

Silver chloride is a common source and intermediate product in many extractive metallurgical processes, for example it occurs in the anode slimes from copper refineries, the residues of leaching processes for base metals, as a product of the chlorination of impure gold—silver bullion, and in photographic waste. A novel process for the leaching and purification of silver chloride, which was devised by Parker et a/.,26 is based on the observation that silver chloride is very soluble in some dipolar aprotic solvents containing chloride ion but is much less soluble when water is present. The very different behaviour of the equilibrium... 

Iodine, recovery of, from silver iodide residues, 2 6, 8 Iodine-131, purification of activity of carrier-free solutions of, 6 166... 

Exchange resins are also employed for the concentration of ions present in very dilute solutions instances are the recovery of silver from photographic residues, chromate from the waste liquor of chromium plating and magnesium from sea water. They have also been used for the separation of rare earths (p. 426), and of uranium, plutonium and radio-active fission products (p. 437), and for plutonium and uranium-233 purification. A striking application was the historic separation of single atoms of mendelevium on a sulphonated polystyrene resin and their elution therefrom, at 87 , with a-hydroxyisobutyrate (Seaborg, 1955). 

Preparation of silver trifluoroacetate from silver oxide and trifluoroacetic acid in water, and purification of the crude evaporation residue by extraction with ether, are described in Organic Syntheses 1 ... 

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