Periodycal #23: Auroras, self-digesting mushrooms and pet kibble

Plus compounds that imply the presence of elements they don't contain

Oct 02, 2024

Welcome to another edition of the Periodycal newsletter! This edition is a packed one as I’ve had a fairly productive month, so there are three new graphics for you to enjoy on auroras, inkcap mushrooms and pet kibble. As well as that there’s a new project I’m quite excited about that I’ve started working on. Plus there’s the usual round-up of chemistry news stories that I’ve found interesting and more!

What causes the colours of the aurora?

Usually, the aurora is only visible closer to the poles than most of us live. However, due to solar storms as solar activity hits a maximum, there’ve been points in recent months where it’s been visible much further away. If you’ve been lucky enough to spot them, here’s a graphic explaining what causes the different colours!

Infographic on the colours of the aurora. Auroras result from charged particles from the sun hitting the Earth’s magnetic field. The particles follow Earth’s magnetic field lines and enter Earth’s atmosphere at the poles. When they enter the atmosphere, the charged particles collide with atoms and molecules in the air. The collision results in the excitation of atoms and molecules, which give off varying colours of light as they lose the additional energy. The different colours of the aurora are caused by the collision of charged particles, usually electrons, with different gases at varying altitudes in the atmosphere. Red is rare and caused by oxygen atoms high in the atmosphere, green is caused by oxygen atoms lower down, and blues and purples originate from molecular nitrogen. — Click to view and download on the Ci site

Self-digesting, sometimes-poisonous mushrooms

September was National Mushroom Month and over the past few weeks, I’ve enjoyed hunting mushrooms in forests with the kids. It’s also an opportunity to discover some interesting mushroom chemistry, and inkcaps, in particular, are fascinating. Self-digesting AND poisonous (but only with alcohol), there’s more in this graphic, and you can see a brilliant time-lapse video of them dissolving here.

Infographic on inkcap mushrooms, titled "Inkcaps: Self-digestion, inks, and poisoning." Most species of inkcap mushrooms appear only fleetingly before self-digesting themselves into a black liquid. They do this to spread their spores. Inkcaps break themselves down by producing the enzyme chitinase in their cells. Chitinase breaks down chitin, the sugar in fungi cell walls that holds them in shape, causing the mushroom to disintegrate into a black goo. This process is called deliquescence. The black liquid produced by inkcaps’ self-digestion can be used as an ink due to the melanin pigment that it contains. Coprinopsis atramentaria, the common inkcap, is not considered edible due to the presence of coprine, which can cause unpleasant symptoms if it is consumed with alcohol. Our bodies metabolise coprine into aminocyclopropanol and glutamic acid. Aminocyclopropanol interferes with alcohol metabolism. It inhibits the aldehyde dehydrogenase enzyme, inhibiting the breakdown of the acetaldehyde that is formed from ethanol. Acetaldehyde build-up causes a flushed face, racing heart rate, nausea and vomiting. — Click to view and download on the Ci site

Cat and dog kibble chemistry

What’s in cat and dog kibble and what makes it so appealing to our furry friends? That’s what this latest edition of Periodic Graphics in C&EN looks at. It includes a look at a key difference between cat and dog kibble, how “cat crack” makes it irresistible to cats, and how compounds from decaying meat are also key.

Infographic on the chemistry of dog and cat kibble.   Kibble is a mix of proteins, carbohydrates, fats, and fiber. Manufacturers also add important vitamins and minerals to keep pets healthy.   Cats have a higher dietary protein requirement than dogs. They also need fewer carbohydrates. Cat kibble protein is often from animal sources so that it contains taurine. Most dogs synthesize sufficient taurine from the amino acids methionine and cysteine. Cats have to obtain it from their food.  Manufacturers add palatants to make kibble appealing to cats and dogs. In cat food, these include pyrophosphate salts. Scientists think they intensify the taste of amino acids in the food. Other common palatants for cats and dogs are the amines putrescine and cadaverine, compounds that decaying meat produces. — Click to view and download on the C&EN site

Ci Concentrates

For over ten years now, I’ve been creating chemistry infographics, so I decided it’s about time I branched out to other media too. So, here it is: the first of a new series of videos, Compound Interest Concentrates, in which I’m challenging myself to condense my graphics into less than a minute. This first one looks at the chemical compounds that colour autumn leaves, appropriately timed as this week is National Fall Foliage week.

Let me know what you think and which graphics you’d like me to tackle next!

Deceptive compound names

Off the back of sharing one of my graphics on chocolate chemistry, the discussion turned to why theobromine has the word ‘bromine’ in its name when it doesn’t contain the element bromine. Here’s the answer, which then kicked off further chat about other compounds whose names suggest elements they don’t actually contain. Find some of the suggestions in the Bluesky thread here!

Theobromine: No bromine Chlorophyll: No chlorine Fluorene: No fluorine Any other examples of compound names that hint at elements they don’t contain? — Click to view full thread on Bluesky

Chemistry news and features

Here’s the regular selection of chemistry news and features I’ve found interesting over the past few weeks:

Doritos dye makes mouse skin see-through – A fascinating finding that rubbing a solution of tartrazine, a yellow food dye used in Doritos, on mouse skin made the skin transparent. Sadly, not an effect you can replicate at home as a much higher concentration of tartrazine than is found in Doritos was used.
Earthquakes may be key to gold nugget formation – The electrical properties of quartz combined with gentle jiggling from earthquakes slowly drags gold particles into nuggets.

That’s all for this month! If you’ve got any suggestions for graphics, or comments about existing ones, please let me know in the comments below.

Expect a Halloween special before the end of October!

Thanks for reading,

Andy