Cooled organic liquids should be allowed to return to room temperature before re-bottling.
Organic liquids used in cold-baths and recovered for reuse should be allowed to off-gas and then stored in self–venting containers.
Effects of Incident
This incident was an injury-free event, however exposure to flying debris and chemicals could have occurred had the container been left to cool on a laboratory workbench during normal work hours. Mixed chemical reactions could have increased severity of incident.
A researcher employed acetone in conjunction with dry-ice as a cooling bath in the distillation of toluene / tetrahydrafuran with aluminum hydride. When the distillation activity was complete and no dry-ice remnants were visible in the liquid, the acetone was recovered for reuse and re-bottled in the original glass container from which it was dispensed. The capped bottle was then placed in the lab's flammable liquids storage cabinet and the lab was closed for the day. Due to the late time of day (approximately 6:00 p.m.) the acetone was not allowed to return to room temperature before being re-bottled, capped, and stored.
Upon initial morning entry into the laboratory, the researcher discovered broken glass and liquid in the flammable storage cabinet. The researcher immediately notified the lab custodian who barricaded the room and made appropriate notifications to EHS personnel. Industrial hygiene staff conducted room air monitoring and once the scene was considered stable, personnel with appropriate PPE verified the absence of chemical incompatibility risks in the flammable storage cabinet. Five bottles of solvent were broken inside the storage cabinet. The broken bottles contained acetonitrile, acetone, pentane and triethylamine. The chemicals were cleaned by the laboratory’s spill response team.
Due to the increased solubility of gas in cold solvents, the acetone, as a result of contact with the dry ice, became saturated with CO2 gas. As the acetone warmed in the capped bottle, CO2 was liberated causing the capped bottle to become over-pressurized and ultimately fail. Glass projectiles from the acetone bottle failure caused the breakage of the four additional bottles of solvent.
Failure to allow acetone saturated with CO2 to return to room temperature and off-gas prior to re-bottling.
Assumption - Acetone solvent when absent of dry-ice crystals is safe to rebottle.
Unexpected condition - CO2 is highly soluble in acetone at low temperatures.
Time Pressure - Acetone was not allowed to return to room temperature because of the late time of day.
Inadequate hazards analysis - Failure to identify CO2 solubility in dry ice/acetone bath resulted in failure to realize pressure hazard when acetone was rebottled and capped.
Corrective Actions to Prevent Reoccurrence
The incident report will be shared with management and laboratory staff.