Adding Dry Ice to Pool

[chem geek]

I bought around 20 pounds of Dry Ice (frozen carbon dioxide) for our Halloween party and wasn't very attentive at feeding the cauldron of water with dry ice to make bubbling and fog (condensed water vapor from the cold carbon dioxide gas). It looked great each time I dumped a chunk of dry ice into the warm water cauldron (a pot with a hot plate under it to keep the water warm), but my lack of attention meant that I had around 8 pounds of Dry Ice left over when the party ended. So I did what anyone with a pool might do...

I dumped the 8 pounds of Dry Ice into the warm pool (around 86 degrees). It bubbled a lot and produced a fog over the area where I dumped it. I figured that it would lower the pH of the pool, but didn't know how much carbon dioxide would dissolve into the pool vs. get bubbled out. It looked like it was mostly bubbling out, but I wouldn't know for sure until the next day...

So now it's the day after the fun experiment and I measured the pH of the pool and sure enough, it's lower by around 0.5 (from 7.5-7.6 to 7.0-7.1). My calculations show that around 1/4th of the carbon dioxide from the dry ice dissolved into the pool to cause the pH to drop. My plan is to just keep my pool open and exposed to air to slowly outgas the CO2. If I had something to aerate my pool more effectively, I'd use it, but I don't. If the pH doesn't move, I'll add some base to get the pH up.

Better living through chemistry!

Richard

[sevver]

LOL, gotta love it. You guys are truly chemistry nutz.

[CarlD]

Richard!!!!

OY!!!

[chem geek]

Yes, it was fun, but oh so educational...

If anyone wants to do this for Halloween, you could probably get by with 5 pounds of dry ice dropping in chunks when trick-or-treaters arrive. However, if you have lots of guests continually over many hours you'll need at least 10 pounds or more. You must use gloves (leather gloves work great) when handling dry ice as it is very cold and will freeze your skin if you touch it for more than a few seconds eventually leading to frostbite -- not as bad as liquid nitrogen, but not something to fool around with. See this website for lots of great info on dry ice.

Be sure to use a heavy old pan/pot -- thick metal, but not aluminum as the acidity of the water (from the dissolved CO2) might ruin the pan. If you don't want to use a hot plate, then just change the water when it gets cool and refill with hot water (hot tap water is plenty hot enough -- even warm water is OK).

I was actually (briefly) concerned that I was contributing significantly to greenhouse gasses by using dry ice so I did some calculations. Since the body exhales about 200 ml of CO2 every minute, this is about 0.36 grams per minute or about a pound per day. So using 20 pounds of dry ice is equivalent to having 20 people breath for a day. One gallon of gasoline produces around 20 pounds of carbon dioxide so using 20 pounds of dry ice is equivalent to using a gallon of gasoline or driving 20-40 miles depending on your MPG. There, now I've made you feel appropriately guilty, so have some fun and plant a tree (one tree absorbs around 1400 pounds of CO2 over its lifetime, mostly in the first 15 years of its growth).

Richard

[matt4x4]

I used to do this yearly on out front lawn, a witch with glowing eues, a couldren kept warm via a hotplate and a "fake" fire underneath, most parents were scared to step on out property, but that might have been because oif the lifesized "working" Guillotine i built which gets "remote controlled" by a friend hiding in the bushes - our display used to take up 2 front lawns (thanks to my old neighbours for the 2nd lawn) , now we're in the country with 5 acres and it takes up this little corner of our front lawn and is no longer as scary. Every year I build more, but I'll be 100 before I can get near filling THIS lawn!

[RavenNS]

Rotfl

You guys crack me up


Happy Halloween