If you have ever attempted to order liquid nitrogen online, then I’m sure you are aware that it’s not quite as easy as it would seem. Not only is liquid nitrogen a volatile substance that requires expensive transportation and careful use, but few online retailers will take the risk to deliver it to individuals not affiliated with a large university, medical facility, or specialized industry. Although some online retailers will let you order liquid nitrogen online if they are located in your vicinity and have the capacity to allow their established customers to request a delivery online, they will only arrive at your location and offer to fill up a vessel that has already been purchased. This means that, regardless of the location, if you don’t work in a career that regularly uses and documents purchase of liquid nitrogen, no retailer will offer to sell you and deliver a full tank of liquid nitrogen.
This would explain why on the "Big Bang Theory", Leslie Winkle, Ph.D.,
an experimental physicist who was one of Leonard Hofstadter's love
interests, was able to flash freeze and shatter a banana for her cereal
(she was unable to find a knife to cut it up). The character works at
the labs at the California Institute of Technology along with the other
scientists on that popular show. She also heats up a cup of instant
soup with a helium-neon laser. Needless to say, these are not a normal
kitchen's food prep accessories, but normal at a lab at Caltech. If you
want to see an example of a Dewar, as described below, watch the Season
1, Episode 5 show, entitled "The Hamburger Postulate", or catch this "Best of Leslie Winkle" video on YouTube.
So now that we’ve addressed the general difficulty of ordering liquid nitrogen online, especially for the layman, let’s talk about the specialized vessels required for storage of liquid nitrogen. The most common storage container is know as a Dewar, and it is a vacuum sealed and insulated vessel specifically designed to slow evaporation of the liquid nitrogen and prolong the life of the liquid. If that is a bit hard to wrap your head around, a common example of the Dewar that sees everyday use in kitchens around the planet is a thermos. Basically, much like how a thermos keeps warm drinks warm and cold drinks cold, a Dewar keeps liquid nitrogen nice and cold. One example of a Dewar is the Brymill Liquid Nitrogen LN2 Storage Tank.
The reason that liquid nitrogen is so often used commercially and medically is its extremely low boiling point and ability to rapidly freeze and cool machinery, food, and even living tissue. That’s why many medical devices rely on it, such as Brymill and Premier liquid nitrogen sprayers, and also why it is commonly used in food preparation and transportation. However, along with the obvious benefits of liquid nitrogen come many risks.
For instance, one should never place liquid nitrogen in a tightly sealed vessel due to the risk of the container exploding—not in the spectacular, Hollywood sense of the word, but improper storage can certainly result in a major safety hazard. Due to its rapid vaporization, liquid nitrogen can quickly vent off huge amounts of pressure. And if that’s not enough reason to be wary around liquid nitrogen, it can also cause very serious burns. Known as ‘cold burns’, contact of human skin with liquid nitrogen can result in an injury much like severe frostbite, and in the worst of cases, result in amputation of fingers, toes, or even require skin grafts on larger areas of the body. Liquid nitrogen also has many helpful medical uses, however, such as in the removal of skin cancers, warts and skin tags. So in conclusion, while liquid nitrogen has many helpful uses, care must be taken in its transport and storage.