Mercury (element)

Mercury is a chemical element with the symbol Hg and atomic number 80 on the Periodic table. It is a heavy metal that is liquid under standard temperature and pressure.

The remaining debris of the Caretaker's array contained mercury, hydrogen, helium, and argon. 

Mercury was used in an instrument called a barometer to measure gaseous pressure. The atmospheric pressure of Taurus II measured 70 milimeters of mercury. 

Background Information

 * The script of the Star Trek: Deep Space Nine episode describes the liquid latinum as having "the consistency of mercury."