How To Make Dry Ice
I know many people who learn about dry ice want to try and make it for themselves at home. I mean, there’s carbon dioxide in the air all around us, right? Why can’t we harness that in some way at home? It’s true that knowing how to make dry ice doesn’t involve all that complicated a procedure.
However, it is a process that requires a good deal of sophisticated equipment. Also, handling dry ice does pose a safety hazard because of its extreme cold temperature. Trying to make something like that around the house can wind up creating an unsafe situation for you and anyone else on the premises.
So how is dry ice really made? The process actually begins with liquid carbon dioxide. Just liquefying carbon dioxide to begin with is difficult because, as we already know, solid carbon dioxide naturally sublimates into a vapor, skipping the liquid step entirely.
Liquefying Carbon Dioxide
Unlike many other substances, liquid carbon dioxide and carbon dioxide gas can exist at many of the same temperatures. In fact, while dry ice becomes a gas at about -78.5°C, liquid carbon dioxide can exist up to temperatures of about 31°C.
So what’s different that makes some carbon dioxide take on a gas form and some remain a liquid at the same temperature? Well, it turns out that the major difference is the pressure being exerted on the substance. At normal atmospheric pressure, carbon dioxide will remain a gas. But if it’s put under enough pressure while also being kept at temperatures below 31°C, a liquid can be obtained.
The Next Step on How To Make Dry Ice
Once liquid carbon dioxide is made, it must be kept at a minimum pressure at all times or it will revert to gas form. Making dry ice actually takes advantage of this characteristic. Removing the liquid carbon dioxide from its pressurized tank will cause it to evaporate quickly.
This evaporation uses so much energy that it will instantly cool the surrounding air dramatically. When this happens, a considerable amount of the carbon dioxide will freeze. This frozen carbon dioxide usually resembles snowflakes and is essentially dry ice.
All that remains is for the flakes to be compressed into a solid block. Also, in order to get the most out of the liquid carbon dioxide, the portion of carbon dioxide that didn’t freeze can be extracted and recycled for later use in the same process.
Forms of Dry Ice
While you’re probably most familiar with dry ice in a block form, there are actually quite a few different ways that dry ice is produced commercially. These forms include various sizes of pellets and a few different types of blocks. Dry ice can also be formed into large blocks and then cut down to meet a customer’s specific requirements.
Depending on what you plan to use your dry ice for, you’ll be better off with one or another of these products. For instance, large blocks of dry ice are used to maintain temperatures when shipping large quantities of frozen foods, while the smaller pellets can be used for anything from meat processing to dry ice blast cleaning.
I hope this has helped you on how to make dry ice.