Buy Now Arsenic in Your Drinking Water Speciation Testing (East)Arsenic exists in two oxidative states in water: either Arsenite (III) or Arsenate (V). Arsenite has a valence of +3 also referred to as trivalent Arsenic. Arsenate has a valence of +5 also referred to as pentavalent Arsenic. When using anion exchange to treat for arsenic it is important to know the valence that is present in the water as most media only remove Arsenate. Arsenic presence in the form of Arsenite must be oxidized into Arsenate in order