#AskAChemist: Turn distill for what?

In this episode of #AskAChemist, I answer a question for mammalogist and field biologist @DNLee. She works with pouched rats and, very shortly, a fog machine.

Yes, a fog machine.

The not-so-secret recipe Dr. Lee’s fog machine uses to generate fog requires distilled water. “Why can’t I just use tap water? It’ll work in the recipe the same,” said Dr. Lee. Water is water, right?

Doctors never do give short answers

H2O is H2O is H2O. Thing is, tap water isn’t just H2O. Tap water contains all kinds of stuff other than H2O. Here in the US of A, our tap water is generally safe to drink partly because we add stuff to our municipal water to disinfect and protect. We also add fluoride to our water for dental heath. Organic compounds are in there too! Our water might be okay to drink, cook with, and bathe in, but it’s not the best choice for fog machines, humidifies, and more sciency (and expensive) scientific instruments. Why?


Solids. All that other stuff besides H20 in tap water can be left behind when water is raptured* inside fog machines. This left behind solid gunk all over the internal parts of a fog machine builds-up with use and funks things up. And not the good kind of funk. To keep the fog machine tip top, you gotta…

Beyonce knows what’s up

…to distilled water. Distilled water has already gone through the rapture – left behind cycle, just not inside the fog machine. In distillation, we collect the raptured* water and condense it to get liquid water. This liquid water is more pure because it’s free of the left behind stuff.

The new hotness

The more distillation cycles tap waters goes through, the more pure it is and the less gunk it’ll leave behind in our fog machines, humidifies, and more sciency (and expensive) scientific instruments. How much is this water upgrade? You can get a gallon of distilled water for <$1 at Walmart. If you want distilled water that’s been verified and comes with a fancy report, ChemWorld offers a 4-pack of 1-gallon jugs for $49.99.

Distillation. OBVIOUSLY.




HIMYM’s Barry gif from Buzzfeed

10th Doctor gif from tumblr

Beyonce gif from tumblr. Enjoy her ‘Upgrade U’ video here

Undercover Brother gif from tumblr

Distillation gif from USGS

TDFW gif from Buzzfeed


DrRubidium is an analytical chemist that spends her days finding needles in needlestacks. Also a science communicator, she focuses on the the science behind everyday stuff and pop culture.

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  1. I’ve seen ice cubes completely sublimate in my freezer, leaving behind a small deposit of solids, presumably mostly salts as a result. Really cool!

  2. I pay 60 cents per gallon for distilled water at a “pure water” store where customers fill their own jugs. People always ask me why I do this. I tell them about the strange oily chemical slick which forms when I brew ordinary black tea in tap water. I suppose I could use the 25-cents-per-gallon bottled water, but I think my brewer has lasted this long because I do use only distilled water in the heating chamber.

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