Dry ice Coolers

I would like to know if i can create a lunch box with dry ice in the wall to keep it cooler for longer then water is it safe and does it require special license
- Yehudah (age 28)
Brooklyn NY USA

You don't need a special license for dry ice, at least around our town. There are a number of things you will have to watch out for, however.

1. Dry ice is very cold, so you can get frost bite if you touch it with moist hands and they stick to it. 

2. Some foods will be ruined by being frozen.

3. It turns into gas rather than liquid as heat reaches it. That gas takes up a lt of volume. You can't put it in a sealed region because the gas will cause an explosion. (My kids used to do that with plastic bottles, but you don't want it to happen with your lunch box.)

4. This may be a surprise, but the latent heat of fusion of dry ice is just over half the latent heat of fusion of ice for a fixed weight. That means that ice soaks up a lot more heat as it melts than dry ice does as it sublimates. So ice is better for keeping a lunch cold.

Mike W.

(published on 09/04/2014)