Chemistry Pic of the Week: King’s Water



A little bit of a spin on the concept of “picture” this week. Instead, it’s a GIF of a freshly prepared batch of aqua regia. We were using it to remove any and all traces of metal from this piece of glassware so we could use it for a sensitive reaction later that day. Aqua regia means king’s water and it is so named because it will easily react with and dissolve what have historically been called “noble metals” like gold.

Aqua regia is incredibly dangerous and corrosive. The gases that come out of solution are also toxic and corrosive. It may be hard to see this, but the bars in the back of this fume hood have been corroded. All we do in this fume hood is make aqua regia and clean glassware. It’s not supposed to ever be removed from the hood, and because it generates gas, it cannot be kept inside of a closed container. Instead we make it in small quantities as needed, and work carefully inside of a fume hood. Minor technical note: There are some compression artifacts that make it look like there are particles on the finger of the person holding it, this is just how the GIF turned out after I made it small enough that it would load easily.

If you want some idea of why we use it to clean glassware, this flask had black iron staining that hadn’t come off after several days in a bath of hydrochloric acid. They disappeared almost instantaneously when we added the aqua regia. This picture was taken a moment after the flask was filled. There is a fascinating story that I’m researching at the moment about aqua regia that will have to wait for another post, so stay tuned for that, some time before the month is out!


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