#9 – Ammonium Chloride | Project Chemistree

#9 – Ammonium Chloride | Project Chemistree

Flask number 9 wins the prize for “most appropriately themed Chemistree decoration, 2018”.

I mean, look at it. There’s a tiny white forest of crystal pine trees with snow! What could be more Christmas-y?

Flask #9 is a really special ongoing reaction – Chemists call them saturated solutions. Have you ever tried to make caramel? You know how you get to that point adding the sugar where no matter how much you stir, you can never get it to dissolve? That’s the point where the water is “saturated” with sugar. The only way to get all the sugar to dissolve is to heat it up.

PhD student, Anthony Carroll was walking past a bunch of stored chemicals in his lab one day when he noticed something about the saturated solutions they often use. On days where it was hotter, there was much less white solid powder down the bottom of the jar. Just like making caramel – if you heat a saturated solution, you can get more solid to dissolve.

The opposite is also true – if you cool something down, then less solid dissolves. It starts to recrystalise.

So Anthony started playing around with the beautiful crystals he found in the ammonium chloride they use to keep pH stable in a bunch of different reactions. He found that if you put enough ammonium chloride in hot water, you could get it to start snowing onto the bottom of the flask when it cools.

Check out the video below to see it in action!

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