Silver halide precipitation

J. C. S., 67, 600.)—This method is used when an ester is not easily obtained by the usual methods owing to steric hindrance or some such cause. The silver salt and alkyl iodide are heated or shaken together with or without an inert solvent, benzene, etc. The precipitated silver halide is filtered off, and the ester separated from the filtrate by distillation or some other method. 

Diorgano tellurium dihalides, when refluxed with silver fluoride in toluene, tetrahydro-furan, or acetone, precipitate silver halides. The diorgano tellurium difluorides crystallize upon cooling the filtrate of the reaction mixture or evaporating the filtrate under vacuum. 

Dimethylaminophenyl 4-Ethoxypheny] Tellurium Dicyanide7 0.78 g (2 mmol) of 4-dimethylaminophenyl 4-ethoxyphenyl tellurium chloride iodide and 0.6 g (4 mmol) of silver cyanide in 30 ml of chloroform are stirred at 20°. The precipitated silver halides are filtered off and the filtrate is concentrated to give the product yield not given m.p. 192°. 

Two grams (0.005 mole) of (-)389-bis(l,2-ethanediamine)oxalatocobalt(lII) iodide3 is suspended in 30 mL of water at 35°, 0.81 g (0.005 mole) of silver acetate is added, and the mixture is stirred for five minutes at 35°. The mixture is then filtered and the precipitated silver halide is washed with 5 mL of warm water (50°). Separately, 2.4 g (0.01 mole) of sodium ciff.m-diammine-carbonato-dicyanocobaltate(UI) dihydrate is dissolved in 10 mL of water. The solution is added to the filtrate and combined with the washings. After removal of the precipitated material, the mixed solution is kept in a refrigerator, whereupon an orange diastereoisomer of the (+ )5g9 form of the carbonato complex precipitates. The product is collected on a filter and washed with cold water. Recrystallization is repeated from water until the CD peak at 24,100 cm-1 reaches a constant value. The crystals are collected on a filter, washed with 50% cold, aqueous methanol, ethanol, and diethyl ether, and finally dried under vacuum. The yield is 0.3 g. Anal. Calcd. for [Co(ox)(en)2][Co(CN)2(C03)(NH3)2]-2H20 C, 21.44 H, 5.16 N, 22.05. Found C, 21.31 H, 5.25 N, 21.78. 

Three grams (0.0075 mole) of (-)589-bis(l,2-ethanediamine)oxalatocobalt(III) iodide1 is suspended in 20 mL of water at 50°. To it 0.225 g (0.0075 mole) of silver acetate is added, and the mixture is stirred for five minutes at 50°. The resulting solution is filtered and the precipitated silver halide is washed with 5 mL of warm water at 50°. To the hot filtrate (combined with the washings) is added 4.4 g (0.015 mole) of sodium cis.cis-diammine-dicyano-oxalatocobal-... 

The complex compoimd AgCNHs) is easily destroyed, i.e., the reaction is reversed, by adding acid to remove dissolved NH3 or by adding a halide ion to precipitate silver halide. 

It may be noted that hydrogen chloride, hydrogen bromide and hydrogen iodide are nearly insoluble in liquid hydrogen fluoride but their solubilities are sufficient to precipitate silver halides from solutions of silver fluoride, Xenon(IV) fluoride is sparingly soluble in anhydrons hydrogen fluoride but xenon(VI) fluoride is very soluble and extensively ionized s. 

Transfer precipitated silver halides to a container labeled for them so that the silver can be recovered. Put the precipitated lead sulfide in a container for heavy metals. Any FAQS that remains may be flushed down the drain, as can the solution from the test for nitrogen. 

A common analysis for the quantity of halide ions (Cr, Br , and I ) in a sample is to precipitate and weigh the halide ions as their silver salts. For example, a given sample of seawater can be treated with dilute silver nitrate, AgNOa, solution to precipitate the halides. The mixture of precipitated silver halides can then be filtered from the solution, dried, and weighed as an indication of the halide content of the original sample. Write the net ionic equations showing the precipitation of halide ions from seawater with silver nitrate. 

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