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Suppose you were trying to invent a bright orange powder that could easily dye clothes and be hard to wash off. Using your knowledge of quantum mechanics you'd design this symmetrical molecule where an electron's wavefunction can vibrate back and forth along a chain of carbons at the frequency of green light. Absorbing green light makes it look orange! And this molecule doesn't dissolve in water.
Yes: you'd invent turmeric!
Or more precisely 'curcurmin', the molecule that gives turmeric its special properties.
The black atoms are carbons, the white are hydrogens and the red are oxygens.
Read on and check out what pure curcurmin looks like.
(1/n)
Ain't it pretty? People extract curcumin from turmeric to use as a food coloring in curry powders, mustards, butters, cheeses, and prepared foods. It's also used in dietary supplements due to its unproven and dubious health benefits.
It doesn't dissolve well in water, but it does in alcohol. If you dissolve some curcurmin in vodka and shine a black light on it, you'll see it's fluorescent! That is: it absorbs the high-energy ultraviolet photons and emits lower-energy green photons... the same kind of light it usually likes to *absorb.* Due to the principle of reciprocity, if a substance is good at absorbing some frequency of light, it's also good at emitting that frequency.
Let's see that fluorescence! Check out my next post.
(2/n)
Here's curcumin dissolved in a hydrocarbon called xylene with ultraviolet light shining on it! It's fluorescent. You can also dissolve it in ethanol, e.g. vodka.
Curcurmin also makes a good pH detector: if you mix it with a base it turns red. This video by @compoundchem illustrates it:
https://www.youtube.com/watch?v=PsVtME5o69I
(3/n, n = 3)
@johncarlosbaez @compoundchem this explains many culinary experiences I had, amazing
@mc - I've spent a lot of time trying to wash turmeric out of my clothes; I should have been using vodka.
@johncarlosbaez @mc i use sanitary alcohol for cleaning stubborn stuff, it’s really great for getting the rubber coating off of “rubberised” plastic.
Dagnabbit, Pascaline! @johncarlosbaez
I loved this entire post, thanks! Fun to read and informative 
As a teacher, I can appreciate that 
@pascaline - thanks very much! That's what I aim for: informative yet fun.
@johncarlosbaez Aha, that explains why when I was washing a turmeric-covered spoon the other day, I saw a brief glimpse of red! I think the water sitting in our faucet can end up a bit basic at times, based on past observations. (Or possibly something else is going on with the chlorine in the water?)
@johncarlosbaez @compoundchem xylene is toxic and absorbs UV light
@johncarlosbaez Huh! This booze I picked up recently has a VERY strong and persistent yellow color. It lists saffron as the top billing flavor/ingredient, but I always wondered how much of the color was really from the turmeric.
Did not think to try shining UV light on it before drinking it all!
@alopex - interesting! Saffron sounds a lot more high-class than turmeric. Next time you get one, break out the black lights for your party!
@johncarlosbaez @compoundchem And tonic water also fluoresces thanks to the quinine!
@johncarlosbaez In Dutch turmeric is called either “kurkuma” (after the Sanskrit name, I guess the source of both the name of the genus and of “curcumin”), “geelwortel” (= yellowroot), or kunyit/koenjit (from Indonesian)
@happydisciple - nice! I was wondering where that word 'curcumin' came from, and I was confused by 'cucurbits'.
@happydisciple @johncarlosbaez Same for Finnish, we also call it kurkuma. :)
(we're also one of the languages that aknowledge Peru as the origin of potatoes in it's name, we call them "peruna")
- @johncarlosbaez The dietary effects are absent, which is a good thing. The oral bioavailability of curcumine is close to zero. If a suspension is ingested with the help of a substance that improves solubility (e.g. piperine extracted from black pepper) or injected, it acts as a poison. So we can enjoy it as a spice and food colorant without having to fear anything.
@johncarlosbaez can it stop oil?
@bracken - I don't know what that means.
@johncarlosbaez When you say "Suppose you were trying to invent a bright orange powder that could easily dye clothes and be hard to wash off" it sounds like you're preparing a protest relevant to current events in the UK.
@johncarlosbaez
In Tamil (the oldest language that is still widely spoken), turmeric is called 'manjal' ( மஞ்சள் ) and the color yellow is also called 'manjal'!
@ThamizhKudimagan - cool! I guess turmeric was one of the most important yellow things for some culture.
