Mercury

The only metal that is liquid at room temperature, and at 13,534 kg/m³ dense enough that steel and lead ballast float on it. That density is why a barometer using mercury is 760 mm tall while a water one would need to be over 10 metres. It has no useful tensile strength or modulus because it is a liquid, and its vapour is cumulatively neurotoxic, which is why it has been designed out of thermometers and switches almost everywhere.

Properties

Density

13,534 kg/m³ — 13.53 g/cm³

Melting point

-38.8 °C

Thermal conductivity

8.3 W/(m·K)

Floats in water

No

Magnetic

No

What it is used for

• Barometers and manometers
• Fluorescent and discharge lamps
• Tilt switches and thermostats (largely phased out)
• Laboratory reference standards

How it compares

Does it rust?

Mercury does not rust — rust is iron oxide specifically — but it does corrode, forming its own oxide or salts over time.

Is it magnetic?

Mercury is not ferromagnetic. It is often assumed to be because it is a metal, but most metals are not — only iron, nickel, cobalt and a few alloys are attracted to an ordinary magnet.