The alteration of arsenopyrite, tennantite and other primary arsenates can form pharmacosiderite. One of the arsenates that he prepared, was arsenic pentoxide. Arsenate-reducing bacteria are bacteria which reduce arsenates. It is an organo-arsenate; less toxic than the inorganic form of arsenates. The other sodium arsenates are NaHAsO and NaAsO, the latter being called sodium arsenate. Leaching with water extracts the sulfate together with the arsenates. Some wood is treated with copper arsenates as a preservative. It is generally assumed that arsenates bind to cysteine residues in proteins. Those minerals may contain hydrated or anhydrous arsenates. Some bacteria obtain energy by oxidizing various reduced substrates while reducing arsenates to form arsenites. Scheele prepared a number of arsenates by the action of arsenic acid on the alkalies. Pharmacolite and picropharmacolite, which are different arsenates, are not associated besides via nomenclature. Phosphates, arsenates and silicates, gemstones and the rock collection are exhibited in hall 4. The products that Paracelsus and Libavius found were all impure alkali arsenates. Arsenates occur naturally in a variety of minerals.