An alloy of sodium and mercury. Readily prepd by adding sodium metal in small portions at a time to mercury. The combination takes place with evolution of much heat. The sodium contents of the amalgam can be varied, as desired, up to about 20% sodium, corresponding to approx Na2Hg. The consistency and mp vary with the sodium content; the amalgam corresponding to NaHg2, 5.4% Na, has the highest mp, +360°.