Silver arsenites

Silver Arsenites.—Silver Orthoarsenite, Ag3As03, is obtained as a yellow precipitate when an aqueous solution of silver nitrate is treated with an alkali orthoarsenite,9 metarsenite10 or tetrarsenite,11 or when ammoniacal silver nitrate is added to an aqueous solution of arsenious... 

Silver Arsenite Sol.—A colloidal solution of silver arsenite has been prepared by the following method.11 A 10 per cent, solution of sodium lysalbinate was added to aqueous silver nitrate and the precipitate separated, washed, and dissolved in an alkaline solution of sodium dihydrogen arsenite. After dialysis, the solution melded on evaporation to dryness a pale yellowish-brown mass which could be dispersed in water to form a sol. 

Yellow precipitate of silver arsenite in neutral solution... 

Silver nitrate yellow precipitate of silver arsenite in neutral solution (distinction from arsenates) ... 

If the silver chloride precipitate is filtered off, washed with distilled water, and then shaken with sodium arsenite solution it is converted into yellow silver arsenite (distinction from silver bromide and silver iodide, which are unaffected by this treatment). This may be used as a confirmatory test for a chloride. 

Trimetho.xyarsine was first reported by Crafts. It was obtained by three methods from silver arsenite and methyl iodide, from arsenic trioxide and tetramethoxysilane, and from arsenic trihalide and sodium methox ide. Better yields have been obtained by applying the method of this synthesis the procedure seems to be generally applicable to the preparation of trialkoxyarsines. 

Characters and Tests.—Heavy, white, glistening powder, or in translucent masses resembling porcelain. Completely volatile at 400° F. Sublimed in a test-tube, it condenses in brilliant octahedral or triangular crystals. Its aqueous solution furnishes a yellow precipitate (silver arsenite) with silver ammonio-nitrate, and a green precipitate (copper arsenite) with copper ammonio-sulphate. These precipitates are soluble in ammonia and in nitric acid. 

When ignited, the yellowish-white silver arsenite turns brown-black metallic silver and silver metarsenate result from the inner molecular redox reaction ... 

Calcium arsenite yields yellow silver arsenite under these conditions. Accordingly, a comparsion test with pure calcium arsenite is advisable when small amounts of arsenate are to be detected in mixture with much arsenite. Calcium arsenite can be detected by treating a portion of the test material on a spot plate with one drop of a 5 % solution of sodium hydroxide followed by one drop of 5 % silver nitrate. The resulting silver oxide is reduced by the arsenic i. 

Aqueorrs Ag precipitates from neutral solutions of arsenites, silver arsenite, Ag3As03, bright yellow, readily solirble in dilute acids or NH3. 

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