Sodium arsenate is the inorganic compound with the formula Na<sub>3</sub>AsO<sub>4</sub>. Related salts are also called sodium arsenate, including Na<sub>2</sub>HAsO<sub>4</sub> (disodium hydrogen arsenate) and NaH<sub>2</sub>AsO<sub>4</sub> (sodium dihydrogen arsenate). The trisodium salt is a white or colourless solid that is highly toxic. It is usually handled as the dodecahydrate Na<sub>3</sub>AsO<sub>4</sub><sup>.</sup>12H<sub>2</sub>O.
The compound can be obtained by neutralizing arsenic acid:
The salt (as its dodecahydrate) is isomorphous with trisodium phosphate. The anion AsO<sub>4</sub><sup>3-</sup> exists at high pH, but below pH 11.5, it converts to HAsO<sub>4</sub><sup>2-</sup> (also written HOAsO<sub>3</sub><sup>2-</sup>).