Safety Warnings
Dry ice causes severe cold burns on contact with skin. Always use tongs or insulated gloves when handling. Ensure adequate ventilation as subliming CO₂ can displace oxygen in poorly ventilated spaces. Never seal dry ice in closed containers.
The cryophorus is evacuated glass that can implode if damaged. Handle carefully and inspect for cracks before use. Thermal shock from rapid temperature changes can cause failure—remove the cold bulb from the bath after freezing occurs to prevent excessive cooling.
Isopropanol and ethanol are flammable. Keep away from open flames and hot surfaces. Use in a well-ventilated area. The cold temperature of the dry ice mixture reduces vapor pressure, but normal safety precautions still apply.
Purpose
Water freezes inside a partially evacuated glass bulb solely through evaporative cooling -- the dry-ice-cooled second bulb acts as a cold trap that continuously removes water vapor, driving rapid evaporation and heat loss from the remaining liquid. Dramatically demonstrates the latent heat of vaporization.
