I dissolved a ≈ 3g sample of high-grade Nickeline (NiAs) in 31% hydrochloric acid. Generated Arsine gas was bubbled and absorbed in a aqueous KMnO4 solution. The leach solution contain mostly Nickel and Arsenic ions, and probably some Antimony, Copper, Iron, etc. Diluting the solution with a lot of water leads to hydrolysis of Arsenic and Antimony to the oxychlorides and oxides.
It was a fine white precipitate, which, upon standing in front of a window for 2 days, turned almost all grey. I search and found nothing about UV light interactions or elemental precipitation such as this situation. Does the light have anything to do with the conversion of Arsenic or Antimony oxychlorides/oxides to elemental Arsenic or Antimony or is it hydrolysis?
Thanks for your time.