www jst umn edu Liquid Nitrogen Liquid Nitrogen

www. jst. umn. edu Liquid Nitrogen

Liquid Nitrogen Bp: -320 ˚F (-196 ˚C, 77 K) Expansion ratio: 1 : 694 Burns – similar to frostbite or thermal buns Explosions (Texas A&M, 2006; $~500, 000) • Relief valve was sealed shut Asphyxiation( 8 deaths/yr in US) • Oxygen deficiency from not being able to breathe normally Liquid N 2 ingestion (18 th birthday celebration, England, 2012) • Emergency surgery to remove stomach after drinking a cocktail containing liquid N 2 www. jst. umn. edu

Liquid Nitrogen Liquid N 2 in the lab Can solidify with a vacuum pump (mp 60 K) Can condense oxygen (bp 90 K) • Liquid O 2 can cause explosions • Don’t leave liquid nitrogen traps open to atmosphere! • If liquid O 2 formation is suspected, alert other sto the danger and evacuate the area. • Allow the vented system to warm to room temperature Can condense argon • Use nitrogen gas instead www. jst. umn. edu Liquid oxygen is pale blue

Controls • Always wear appropriate PPE (cryo gloves, lab coat, and goggles) and never allow any unprotected part of the body to come into contact with LN 2 or any uninsulated vessels or pipes. • Do not overfill vacuum flasks and never store LN 2 in a sealed container at a temperature above the BP of LN 2. • Always inspect and maintain vacuum flasks. If they are cracked, they may fail explosively. • Eliminate sources of ignition around the LN 2. The risk of O 2 condensation is also reduced when working with smaller quantities of LN 2. • If pale blue liquid O 2 is seen, remove LN 2 traps (if any), flammables, and any ignition sources and let O 2 boil off slowly. www. jst. umn. edu

References • Material Safety Data Sheet: Nitrogen, Refrigerated liquid. <http: //www. liquidnitrogenservices. com. au/safety/ ln 2_msds_e 1. pdf> • Asphyxiation with liquid nitrogen – hazard alert, Monash University. <http: //www. monash. edu. au/ohs/topics/hazardalerts/liquid-nitrogen-asphyxiation. html> • Standard operating procedure (SOP) for handling cryogenic (liquid nitrogen). <https: //eee. uci. edu/programs/chemstockroom/SO P/Liquid%20 Nitrogen%20 SOP. pdf> www. jst. umn. edu