![]() If you are ever working with a laboratory vacuum line and find a pale blue liquid in your trap, immediately replace the trap and back away. Liquid oxygen is exceedingly dangerous and reacts violently with most organic substances, including Teflon® tape, vacuum grease, and organic solvents. Liquid oxygen - If a constant stream of air is pulled through a vacuum trap cooled with liquid nitrogen, liquid oxygen may condense in the trap (see item 1b above!).Fire and Explosion - While nitrogen is a non-flammable inert substance, some cryogens, such as hydrogen are flammable.See the carbon dioxide entry for more on this topic. NEVER STORE CRYOGENS IN A SEALED CONTAINER. Pressure Explosion - Cryogens are at their boiling point or sublimation point which means that they are rapidly converting from liquid or solid into large volumes of (invisible) gas.Perform hazard/risk assessments of your cryogen use to decide if you should install oxygen deficiency alarms in the areas where cryogens are stored or handled. ![]() The vapors are generally heavier than air, so stairwells and basements can be particularly hazardous. Do not enter an oxygen deficient area, even to rescue someone. If gas is formed in an unventilated enclosed area, death or coma from oxygen deficiency can result. Asphyxiation - Small amounts of liquid cryogen expand into very large volumes of gas, displacing oxygen.Seek medical assistance for severe cases. In the event of contact with cryogens, use appropriate first aid procedures such as warming the affected areas with lukewarm ( never use hot) water. Therefore, splash goggles, non-porous aprons and insulated gloves which can be quickly removed are always recommended when handling liquid or solid cryogenic substances. Frostbite can occur quickly, especially if the liquid nitrogen saturates your clothing or gloves. Brief exposure to liquid nitrogen can cause painful blistering. Frostbite - Liquid nitrogen freezes human tissues within seconds, a behavior exploited by dermatologists to remove warts and other cosmetic blemishes.When glass Dewars are dropped or treated roughly, they tend to implode with a loud bang, so most laboratory Dewars are enshrouded in a plastic mesh, aluminum jacket, or tape to contain shrapnel.Ĭryogens present a number of serious physical and health hazards: While Dewar flasks can be made out of steel or plastic, common laboratory ones are usually made of silvered glass. These have have a loose-fitting cap to vent the evolved gases while preventing air and moisture from entering. Liquid cyrogens such as liquid nitrogen are stored in special vacuum-jacketed vessels called Dewar flasks (named after the first person to liquify helium, James Dewar) which are essentially fancy versions of a common Thermos® flask. ![]() Handling of cryogens requires special equipment and training. For example, chemists will often use a slush bath made of acetone and solid carbon dioxide to maintain a temperature of -78 ☌. Cryogens can be pure substances or mixtures of different substances. 4.2 K = -270 ☌ = -450 ☏), and carbon dioxide (a solid that converts directly to gas at 195 K (-78 ☌ = -109 ☏). ![]() You can get metal-cased Dewars like these from Safety Emporium.Įxamples of common cryogens include liquid nitrogen which has a boiling point of 77 Kelvin (-196 ☌ = -321 ☏), liquid helium (b.p. ![]()
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