HANDLING LIQUID NITROGEN

Liquid nitrogen is manufactured by cooling down air to a temperature of 77 K.Liquid nitrogen is very common and easy to obtain, if you know where to look. It is used by hospitals, physicians, cattle breeders, universities, factories, and welding shops. Liquid nitrogen can be obtained from these sources for a minimal cost.

Small quantities of liquid nitrogen can be stored in Dewar bottles. Dewar bottles are hollow-walled glass-lined containers which provide excellent insulation.Dewar bottles will keep liquid nitrogen for a fairly long period of time. If you do not have a dewar, a standard Thermos bottle with a stainless steel shell will work fine for transporting and storing small amounts of liquid nitrogen for a short time. Thermos bottles have screw-on caps. CAUTION !!! THE CAP MUST NEVER BE SCREWED ON AT ANY TIME LIQUID NITROGEN IS IN THE BOTTLE. If the cap is not vented the liquid nitrogen will boil and build up pressure until the bottle EXPLODES.

Safety procedures for handling liquid nitrogen:

Liquid nitrogen is a hazardous substance. If misused it may cause, frostbite,eye damage, torn flesh, or asphyxiation. FOLLOW THE FOLLOWING SAFETY RULES:

• Keep away from students.

• Always wear safety goggles at all times.

• Use tweezers to handle superconductors, magnets, or other small, cold objects. Plastic tweezers are useful but should be tested for embrittlement (see last caution) before use in classroom.

• Wear insulating gloves when handling liquid nitrogen or large, cold objects.

• Use liquid nitrogen only in well ventilated places.

• Do not allow any liquid nitrogen to touch any part of your body.

• Item in contact with liquid nitrogen becomes Extremely Cold. Do not touch any item that has been immersed in liquid nitrogen until it has warmed to room temperature.
• Do not store liquid nitrogen in any container with a tight fitting lid. A tightly sealed container will build up pressure as the liquid boils and may EXPLODE after a short time.

• Many substances become brittle and may shatter when cold, sending pieces of the material flying. Avoid common glass and large, solid plastics.

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