Atomistry » Arsenic » Chemical Properties » Silver Thioarsenates
Atomistry »
  Arsenic »
    Chemical Properties »
      Silver Thioarsenates »

Silver Thioarsenates

Silver Orthothioarsenate, Ag3AsS4, is formed as a dark brown precipitate when an aqueous solution of silver nitrate is treated with sodium orthothioarsenate. If, however, silver nitrate is added to a solution of sodium orthothioarsenate, silver orthothioarsenate is not formed but silver sulphide is precipitated and arsenious acid, nitric acid and sodium nitrate are formed in solution. The reactions involved probably take the following course:

2Na3AsS4 + 6ArNO3 = 3Ag2S + As2S5 + 6NaNO3
As2S5 + 10ArNO3 + 8H2O = 5 Ag2S + 2H3AsO4 + 10HNO3

the nitric acid then liberates hydrogen sulphide from the thioarsenate and this reduces the arsenic acid: -

2Na3AsS4 + 6HNO3 = 3H2S + As2S5 + 6NaNO3
H3AsO4 + H2S = H3NaO3 + H2O + S

the sulphur being partly oxidised to sulphuric acid, which is also found in the solution. The presence of mineral acid in the thioarsenate solution favours the above decomposition; in ammoniacal solution arsenic acid remains in the solution and no arsenious acid is formed.

Silver orthothioarsenate readily decomposes on heating, yielding sulphides of silver and arsenic and free sulphur. It is found in Nature as a yellow or orange-red mineral, generally in the form of powder, known as xanthoeonite, and sometimes associated with selenium as rittingerite.

Last articles

Xe in 6AYK
Xe in 6QII
Xe in 6ASM
Xe in 5NSW
Xe in 6FY9
Xe in 5O1K
Xe in 5O27
Xe in 5M69
Xe in 5KPU
Xe in 5I63
© Copyright 2008-2020 by atomistry.com
Home   |    Site Map   |    Copyright   |    Contact us   |    Privacy