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