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Ci Newsletter #15: Guinness, green rivers, and crocus imposters

Andy @ Compound Interest
Andy @ Compound Interest
A day later than usual, here’s the latest Ci Newsletter, this week with a definite Spring theme. First, there’s a new graphic with a focus on crocus chemistry, along with a nod back to an older graphic on flower aromas. Then there’s some Guinness chemistry for St Patrick’s Day, along with some thoughts on the dyes some cities use to turn rivers green. Along with all that, there’s a new Women in Chemistry History graphic and the usual round-up of chemistry news and features from elsewhere on the web.

Crocuses, saffron, and poisonous imposters
Click to view and download the graphic on the Ci site
Click to view and download the graphic on the Ci site
I’ve learned several fun facts about saffron this week, both during and after making this graphic. Firstly, I hadn’t realised that saffron is obtained from the stigmas of one species of crocus. Secondly, I hadn’t realised that a town not too far from me, Saffron Walden, does indeed take its name from its historical production of saffron.
This new graphic focuses on the chemistry of crocus colour, and also takes a look at the potential dangers of confusing the different plants which are nicknamed ‘autumn crocus’.
I also made a crocus pH indicator from one of the purple crocuses in our garden, worth it for the vibrant blue produced!
Andy Brunning
#GardenIndicators, purple crocus edition. Beautiful blue indicator solution, turning a vibrant red in acidic solution and yellow in alkaline solution @CrocodileChemi1 https://t.co/GMleBUd2IT
St Patrick's Day: Guinness
Click to view and download the graphic on the C&EN site
Click to view and download the graphic on the C&EN site
With St Patrick’s Day coming up here’s an old classic from the C&EN Periodic Graphics archive: a look at the chemistry of a pint of Guinness, including what’s in the bubbles and why they appear to fall.
St Patrick's Day: Green rivers
Chicago's river dyed green for St Patrick's Day
Chicago's river dyed green for St Patrick's Day
Since 1962, Chicago has dyed its river green for St Patrick’s Day. Initially, this was done using fluorescein, a dye commonly used to detect leaks in plumbing, but environmental concerns led to a switch to a different dye in 1966. Is dyeing a river green a sensible thing to do from an environmental perspective? Almost certainly not, but the dye used would definitely be a factor in this.
Despite my best efforts to find out what this dye is (i.e. I googled it for a bit), Chicago officials seem to have done a remarkably good job of keeping its identity under wraps. Some clues have been divulged: it’s a vegetable-based dye, an orange powder when dry but green when mixed with water, and the EPA has stated that it’s “a food-grade dye also used in medicine, as the colourant for antifreeze and as a tracer dye”.
An investigation by Isaac Green, then a student in the Institute of the Environment and Sustainability at Western Michigan University, concluded that it’s probably BrightDyes Fluorescent FLT Yellow/Green that’s being used, as this is used for a similar purpose in other cities. But there’s still no definite confirmation of this. If any readers are in the know, do feel free to get in touch…
Women in chemistry history
Click to view and download the graphic on the Ci site
Click to view and download the graphic on the Ci site
For International Women’s Day last week, I added another edition to the Women in Chemistry History series of graphics. This one features another 12 women from chemistry history with short summaries of their achievements. To address the inevitable ‘Where’s Marie Curie?’ question these always seem to be met with, you can find her in part 1, and others in parts 2 and 3.
If you’ve got ideas for women in chemistry history who I’ve yet to feature, do let me know!
Flower aromas
Click to view and download the graphic on the Ci site
Click to view and download the graphic on the Ci site
Spring is getting going in the northern hemisphere, and as the flowers start to bloom here’s a reminder of some of the different key compounds that contribute to their aroma. It’s worth noting that this is somewhat reductive – many different compounds contribute to flower aroma – but highlighting some of the most significant makes for some interesting comparisons.
Chemistry news and features
Massive Australian wildfires caused new damage to the ozone layer
Learning about women chemists is an entitlement
That’s it for this fortnight – as always, let me know about any thoughts or suggestions you’ve got for this newsletter. Graphics on solar panels, arrows in chemistry and buffer solutions are in the pipeline, and should be featured in coming editions!
Thanks for reading,
Andy
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Andy @ Compound Interest
Andy @ Compound Interest @compoundchem

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