Poor Man's Liquid Nitrogen

Liquid nitrogen is useful for snap freezing cells ready for storage. Our lab doesn't order it in because we don't use enough, so whenever I need it, I have to go to the other labs and 'borrow' it. I cycle between 3 labs, the mycotoxin lab, the virus lab and the fungus lab. They're usually nice enough to give it to me but I always feel bad, because liquid nitrogen is an ever-diminishing commodity.

The other day though, I came across a recipe for Poor Man's Liquid Nitrogen. It's not as good, but works as a substitute. What you need is some dry ice (easier to get than liquid N2) and isopropanol, which is rubbing alcohol. Dry ice comes in chunks that look a little bit like white Cheetos and it tends to stick to things in an unpleasantly cold way. Kind of like a tongue on a frosty pole.

So what you do is punch some holes into a few paper cups and get a small styrofoam box.

Put the cups inside the box and pack the gaps between them with dry ice. Then pour the isopropanol over everything so that the cooled fluid will fill up in the cups. If you don't have isopropanol, you can use 95% ethanol. If you don't have 95% ethanol, you could probably make do with Bacardi 151. Soju would not work, as the lower alcohol content would cause the bath to soldify.

This is what it should look like if things are going well. The alcohol stays as a liquid at very low temperatures, which allows you to dip things in it and snap freeze them. Right now the alcohol is bubbling from the carbon dioxide gas, but is extremely cold. If you put a flower in it and then drop it on the ground, it will shatter. Be careful not to get it on your skin though, because unlike liquid N2, it will cling and give you frostbite.

You can do a regular liquid nitrogen science show with it if you are an elementary to middle school teacher. Use things like rubber bands, super balls and fruit. To make mist like I have in the photo above, just add hot water. Adding detergent will create an endless supply of bubbles, which at first is very entertaining, but later becomes worrisome.

You should refrain from doing these sorts of things in the presence of your lab professor. Unfortunately they're only interested in the kind of science that you can publish. If you do get busted though, just do what I do. Smile and say "Gee, Korean CO2 is really strong!"

Good luck!