Arsenic cannot be completely separated from either its aqueous
hydrochloric acid, or from a solution to which ammonium oxalate has been
added in excess. From its aqueous as well as from its oxalate solution,
a portion of the metal may be separated, but if the current is passed
through its hydrochloric acid solution for a sufficient length of time,
all the arsenic will be volatilized as arsenious hydride (AsH_3).