Q: You are using a Schlenk line and when you remove the Dewar from the trap, you see a light blue color. What should you do?
🔍 Understanding the Situation
Seeing a light blue color in the cold trap is a strong indication of condensed liquid oxygen (O₂).
⚠️ Important: Liquid oxygen is a highly powerful oxidizer and can react explosively with organic substances. Extreme caution must be taken immediately.
🧪 What Not to Do
- Do not admire the color – it is visually interesting but chemically hazardous.
- Do not empty the trap – rapid release may cause sudden flash evaporation, producing an oxygen-rich environment and increasing explosion risk.
- Do not use a heat gun – rapid heating could lead to violent boiling and possibly an explosion.
❌ All these actions increase the risk of uncontrolled ignition or explosion.
✅ Correct Procedure
The safest course of action is to put the Dewar carefully back on and allow the trap to slowly warm up, ideally in a well-ventilated area or fume hood.
- Gently isolate the trap from the Schlenk line.
- Move the trap to a safe, open environment free of flammable materials.
- Let it warm gradually to room temperature — this allows the liquid oxygen to evaporate naturally.
This avoids any sudden pressure changes or oxygen concentration spikes that might otherwise lead to fire or explosion.
✅ Final Answer
Put the Dewar carefully back on and allow the contents to slowly heat and evaporate on their own. This is the safest way to handle condensed liquid oxygen and avoid hazardous situations.
✔ Correct Choice: Option 4