Platinum

Denser than gold at 21,450 kg/m³, and one of the few metals that can be worked as a crucible material for molten glass and oxides because it neither melts nor reacts. Platinum resistance thermometers are the defining instrument of the international temperature scale from -200 °C to over 900 °C, precisely because the metal is so reproducible. Most of the world's production is not jewellery but catalysis, which is why catalytic converter theft tracks the metal price.

Properties

Density

21,450 kg/m³ — 21.45 g/cm³

Melting point

1,768.3 °C

Tensile strength

125–240 MPa

Young's modulus

168 GPa

Thermal conductivity

71.6 W/(m·K)

Thermal expansion

8.8 µm/(m·K)

Floats in water

No

Magnetic

No

What it is used for

• Catalytic converters and fuel cell catalysts
• Laboratory crucibles and thermocouples
• Spark plug electrodes
• Jewellery

How it compares

Does it rust?

Platinum does not corrode in air or water. That chemical inertness is much of why it has been used for coinage and contacts for millennia.

Is it magnetic?

Platinum 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.