Triple Point Cell - Physics Demonstrations - Triple Point Cell | Physics Undergraduate Labs

Dry ice (solid CO₂) is at -78.5°C and will cause severe frostbite on contact with skin. Always use insulated gloves or tongs when handling. Ensure adequate ventilation as sublimating CO₂ can displace oxygen in poorly ventilated spaces. The dry ice/alcohol mixture is extremely cold—avoid contact with skin or eyes.

Purpose

Students observe all three phases of water coexisting in thermodynamic equilibrium at the triple point (273.16 K, 611.657 Pa). Connects phase diagrams to physical reality and demonstrates the Gibbs phase rule prediction of zero degrees of freedom.

Trans-Sonics Equiphase triple point cell: polished stainless steel cylinder with glass reentrant thermometer well protruding from the top, and blue plastic protective cap shown beside it

Figure 1: Trans-Sonics Equiphase triple point cell with glass reentrant thermometer well. The blue cap protects the well during storage.

Safety Warnings

Warning: Dry Ice Handling

Purpose