Thursday, December 27, 2007

Carbonates and housecleaning

It's winter break. I'm home with the four-year-old, building a lot of things with Legos, playing snow leopards (we've been watching the Planet Earth series), and pretending to do some year-end cleaning.

There are a few household maintenance things that I... well, I should do them more often than I do. Turn the mattress on the bed, for instance. Change the air filter on the heating system. And change the wicking filter on the humidifier.

We got a medium-sized humidifier during the summer of 2002, when we were about ten miles from the edge of one of the many fires that were burning in the western US. Normally we cool our house in the summer by simply opening the windows at night. We live at 7000 feet, and it gets pretty cool here. But during the fire, the smoke settled into the valleys at night, and we kept the windows closed to keep it out. I had just finished my second year teaching here, and I had taught Earth Systems Science four times in a row, and I was all psyched to try cooling using evaporation. I wanted a swamp cooler, but I had no idea what I was looking for, so I came home with a humidifier and a fan. I'm not sure the humidifier did anything for the temperature, but it made the air in the house easier to breath. So now we usually turn it on at night, and fill it with water that we collect in old yogurt containers when we're getting ready to get into the shower. (Yes, I know a grey-water system might have been a better use, and might have allowed us to have a lawn that consists of more than twelve blades of buffalo grass. But I'm not a plumber. That's on the list of renovations I want to do.)

Anyway, whether or not the humidifier is useful, it only works when water can soak into its wick and then evaporate. That works for a while, but eventually, minerals precipitate on the top of the wick, and it needs to be replaced. So one of my missions yesterday was to find a new wick for the humidifier.

My first try was the locally-owned hardware store where I had bought the humidifier. They still carried the wicks, but they were out. So I tried Wal-mart. No luck; they only carried a handful of humidifiers. Same with Home Depot. In fact, the guy working there rolled his eyes and showed me the shelf full of DE-humidifiers that the main office kept sending them.

"They don't understand 25% humidity," he told me.

"Are they in Houston?" I asked.

"Atlanta," he replied.

So: three places in town that sold hardware, and no luck finding the wicks. I went home and looked at the crusty stuff on the wick, and thought cranky thoughts about the precipitation of calcite and other annoying non-silicate minerals. At least, I figured it was probably mostly calcite. Calcium is by far the most abundant cation dissolved in the nearest river, and even though my groundwater comes from a poorly sorted sandstone, I figured calcite was the most likely mineral. No acid to test it, though...

Wait a minute.

No, I don't keep a stash of hydrochloric acid at home. (Four-year-old in the house.) But I do, however, keep vinegar around. And vinegar's acidic.

In fact, I thought, maybe I could just clean the wick with vinegar. Dissolve off the precipitates, and put it back in the humidifier, good as new.

So I pulled out the wick and put it in the bathtub, and brought the bottle of vinegar upstairs. I poured a little vinegar on the precipitates, and...

Oh, yes. The satisfying FIZZZZZZZZZZZZZ of calcite in acid.

I poured more vinegar on it. It fizzed some more.

I plugged the tub, and kept pouring vinegar, trying to think of a way to make sure the vinegar had time to dissolve as much carbonate as possible.

Half an hour later, I had orange vinegar in my bathtub (not sure where the orange came from; I don't think there's much iron dissolved in my water), and an empty vinegar bottle.

The wick is still pretty crusty, and very soggy, and still needs to be replaced.

Maybe I'll have to try HCl next time.


Dr. Lemming said...

What is the bathtub made of? And how big is this wick, anyway?

Kim said...

The bathtub is plastic. And the wick... it's about 20 cm by 30 cm. It would have fit in a sink, but the bathroom was the nearest room, and the bathtub was the nearest Water Containment Device. Something smaller would have been better, though.