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Ci Newsletter #7: Chemistry advent calendar & Thanksgiving chemistry

Andy @ Compound Interest
Andy @ Compound Interest
Welcome to the latest Ci newsletter! This fortnight’s edition pre-emptive festive edition includes Thanksgiving food chemistry, chemistry advent countdowns, and some interesting discussion on whether anyone knows what colour gaseous potassium is.
As you’ll have noticed, this edition comes a day later than usual. I’ve decided to shift the usual publication day of these newsletters to a Tuesday, as my Mondays are fairly hectic and I was finding myself struggling to get these together on time to go out. So keep an eye out for the newsletters on every other Tuesday from now on!

Chemistry advent calendars
December is almost here, which would usually mean time for another edition of the Chemistry Advent calendar I’ve been producing most years. As I’m still adapting to life with two children instead of one, however, there won’t be a new advent countdown this year. However, there are still plenty to choose from from the past editions: Christmas chemistry, an advent calendar of periodic tables, or a chemistry history countdown.
If you’ve got any ideas you’d like to see for a future edition of chemistry advent, let me know and I’ll bear them in mind for future years!
What colour is gaseous potassium? Who knows!
Still from a video on Andryj Borys's "Schlenk Line Survival Guide" website
Still from a video on Andryj Borys's "Schlenk Line Survival Guide" website
You’re probably familiar with the fact that potassium ions give a lilac flame in a flame test, but like me, you might not have given much thought to what colour gaseous potassium is. The above image, taken from Andryj Borys’s video, claims to show gaseous potassium in the process of forming a potassium mirror, showing a glorious purple colour.
However, after sharing this on Twitter, it’s become clear that whether or not it’s actually the gaseous potassium causing the colour is subject to some debate:
Peter Scott
@ndbrning Britannica says vapour is green.
Maybe they are wrong, but this from 1874...
I've done this a hundred times and always thought the blue stuff floating about was some other compound. Maybe @SellaTheChemist has some gossip.
SellaTheChemist still wears his mask
@peterscott1965 @ndbrning I've never noticed the vapour to be coloured. The film of metal is bluish. Maybe I should seal some up and put in an oven. What could go wrong?
Schrödinger's Prat
@ndbrning @SellaTheChemist @peterscott1965 It should be green if you're vaporising it without oxygen. I've briefly seen it while making a mirror (before it deposited) and there is one guy who filmed it for YouTube, by reacting it with water without oxygen present.
So, what colour is gaseous potassium? There doesn’t seem to be a clear verdict! If anyone reading this newsletter can shed any light on this apparent mystery, let me know…
Thanksgiving chemistry
Click to view the full graphic on the Ci site
Click to view the full graphic on the Ci site
With Thanksgiving coming up this week, here’s one for any US-based readers who are soon to be tucking into a turkey! The compounds shown in this graphic are products of the Maillard reaction, which I also have a separate graphic on here.
Growing sodium chloride crystals
If you’ve experienced the joy of growing copper sulfate crystals then here’s a trickier challenge: growing sodium chloride crystals. “How hard can growing crystals of the salt we all have sitting in the kitchen be?”, you ask. Well, not hard at all, actually, but growing large ones like these spectacular examples is a bit trickier because imperfections form quite easily.
Want to have a go at making similarly beautiful sodium chloride crystals? There are detailed instructions on how to do so on the Crystalverse website (and they’ve got a guide to growing copper sulfate crystals, too, if you’d prefer to keep it simple).
The chemistry of ice and deicers
As the colder months start to creep in in the northern hemisphere, here’s a couple of seasonal graphics from the C&EN Periodic Graphics archive: one on snow and ice, and another on the various compounds used as deicers.
Chemistry news & features
Textbook electronegativity model fails when it comes to explaining bond strengths
The science of breast milk and baby formula
C&EN’s 2021 holiday gift guide
Please do share these newsletters with friends and on social media if you’re enjoying them, and feel free to hit the reply button and get back to me with any comments or suggestions.
Thanks for reading,
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Andy @ Compound Interest
Andy @ Compound Interest @compoundchem

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