Home > chemistry, Nature, Science > Cold, damn cold.

Cold, damn cold.

After writing much of these posts and then showing off my work, my wife, more often than not, will ask questions of stuff that I never even considered. In telling her about water bears, she just had to ask how they managed to freeze the water bears to near absolute zero. This eventually led to me looking up how liquid nitrogen is made (it’s actually a really cool process, just you wait) and then I started looking at other stuff related to the cold. Which, unfortunately is going to lead to a meandering totally disorganized post. So strap yourselves in because in the words of Martin Lawrence, “Shit just got real.”

When looking stuff up about water bears, I wanted to learn more specifically about how they are able to survive being frozen. It turns out that when temperatures drop water bears and other cold-blooded animals make chemicals known as cryoprotectants. These cryprotectants lower the freezing temperature of cells to prevent the damage caused when cells freeze and crystallize. It’s crazy that these animals can go so far as changing their body’s chemical make up to survive.

Along with cryoprotectants many cold-blooded animals will bury themselves during winter months. Many will do this in the mud at the bottom of rivers or lakes. Cold water is more oxygenated than warm water and the animals actually get all the oxygen they need through their skin.

Cryoprotectants are actually administered to those who choose to be cryogenically frozen. This is to avoid cell damage when the water in the body freezes and crystallizes. Despite the widespread knowledge of the process of cryogenic freezing, only about 200 Americans have actually gone through the process in the forty years that its been around. Instead of being frozen before death occurs in hopes that future medicine will be able to cure whatever ailment the patient has, a person has to phyisically die in order to be preserved. The hope is that later science will be able to not only cure the ailment but also reverse the death. The theory behind all of this is that the brain may be able to retain long term memories for a short time after the body has died.

Unfortunately, one of the big problems with cryonic freezing, is that the cryoprotectants can protect the body from freezing, at the cost of essentially poisoning it. However, it’s assumed that the poisoning effect will be easier to undo than the cell damage that would otherwise occur.

Oddly enough, the best way to pay for the staggering costs of the initial freezing, not to mention the ongoing cost of storage, is to use life insurance to cover it. Apparently if you set up a plan when you’re young, freezing can actually be quite affordable. I’m setting up an account for my daughter first thing Monday. I can’t wait to see the look on my insurance agent’s face when I ask her about it.

Morbidly, I wanted to find out more about what happens to cells when they get frozen. it turns out that when people get frostbite, it’s actually the result of a defensive measure taken by the body. When the extremities are subjected to very cold conditions, the body will dilate the blood vessels going to those extremities. Hence, the extremities slowly undergo cell death due to a lack of oxygen and also freeze. The body will choose to kill off a portion of itself in order to keep the rest alive. While not exactly the same, this reminds me of the way that the body will sometimes cause a person to faint. If blood vessels dilate for some reason (say a dashing young southern gentleman chooses to call upon me and kisses my wrist), blood pressure will happen to drop. The brain will sense this and choose to cause the body to pass out so that the head (and the brain encased so deliciously within that head) will drop down. Less pressure is then required to drive blood to brain. The brain therefore saves itself by shutting down part of the body.

If the body is subjected to extremem cold for too long, the blood vessels will eventually tire out. This causes a surge of blood flow to the extremeties which makes people believe that they’re warmer than they actually are. This is combined with the hypothalamus shorting out. The hypothalamus usually regulates body temperature, and when it shorts out people think that they’re warmer than they are. A number of people who die of hypothermia are found having shed their clothes because of this.

So in much less depressing SCIENCE!, the way they make liquid nitrogen is awesome. If you like sauce it’s also awesomesauce.  First, they have to liquid air. You can do that by taking air air and cooling it down a bunch. The easiest way to do that is to compress it down a lot. But according to PVT, by lowering the volume, the pressure and temperatures have to go up. To counteract this, the air is cooled in a heat exchanger and then vented into another chamber to begin the process again. It’s repeated again and again until droplets are formed.

Once you have liquid air, all you have to do is distill off the other elements that make up air, and any hillbilly worth his moonshine knows how to distill. What you are left with is about 20% liquid oxygen and 79% liquid nitrogen and 1% other stuff. Once made, liquid nitrogen has to be kept in a special container that lets it vent occasionally. Liquid nitrogen will generally stay a liquid for quite a while if pressurized correctly. However, unless kept at -331 F, ambient temperature will slowly cause some of it to revert to its gaseous form. This can cause a bit of a problem since gaseous exerts a tremendous amount of pressure (nearly 700 times as much as liquid kind). Unless liquid nitrogen is kept in a ventable container, it can rapidly decompress and cause the container it’s in to explode, like a monkey in space.

Bonus! In searching for the answer to how liquid nitrogen is made, I found this neat little website which lets you run an applet that shows PVT in action. Go ahead and start wasting time with it.

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