The arsenate ion is AsO43&#8722. An arsenate (compound) is any compound that contains this ion.The arsenic atom in arsenate has a valency of 5 and is also known as pentavalent arsenic or As[V].Arsenate resembles phosphate in many respects, since arsenic and phosphorus occur in the same group (column) of the periodic table. In acidic conditions arsenate exists as arsenic acid, H3AsO4;in weakly acid conditions it exists as dihydrogen arsenate ion, H2AsO4&#8722;; in weakly basic conditions it exists as hydrogen arsenate ion HAsO42&#8722;; and finally, in basic conditions, it exists as the arsenate ion AsO43&#8722. Arsenate can replace inorganic phosphate in the step of glycolysis that produces 1,3-bisphosphoglycerate, yielding 1-arseno-3-phosphoglycerate instead. This molecule is unstable and quickly hydrolyzes, forming the next intermediate in the pathway, 3-phosphoglycerate. Therefore glycolysis proceeds, but the ATP molecule that would be generated from 1,3-bisphosphoglycerate is lost - arsenate is an uncoupler of glycolysis, explaining its toxicity.[1]. Some species of bacteria obtain their energy by oxidizing various fuels while reducing arsenates to form arsenites. The enzymes involved are known as arsenate reductases. In 2008, bacteria were discovered that employ a version of photosynthesis with arsenites as electron donors, producing arsenates (just like ordinary photosynthesis uses water as electron donor, producing molecular oxygen). The researchers conjectured that historically these photosynthesizing organisms produced the arsenates that allowed the arsenate-reducing bacteria to thrive. (Wikipedia). Arsenic acid is the chemical compound with the formula H3AsO4. More descriptively written as AsO(OH)3, this colorless acid is the arsenic analogue of phosphoric acid. Arsenate and phosphate salts behave very similarly. Arsenic acid as such has not been isolated, but only found in solution where it is largely ionized. Its hemihydrate form (H3AsO4_а__H2O) does form stable crystals. Crystalline samples dehydrate with condensation at 100  C.