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Terpenes unite the graphics for day 21 of #ChemAdvent

Menthol in candy canes is responsible for the cooling sensation in your mouth when you eat one ❄️

The muddy flavour of carp is dominated by the compound geosmin, another terpene 🐟

Infographic on candy canes. The chemical structures of sucrose and menthol are shown. Menthol from peppermint triggers cold-sensitive receptors when eaten, making your mouth feel cold.

Infographic on carp. The earthy flavour of freshwater fish is due to the compound geosmin, produced by bacteria. The structure of geosmin is shown.

Some cracking chemistry for day 20 of #ChemAdvent!

First up are Christmas crackers, taking advantage of friction-sensitive silver fulminate to deliver a big bang 💥

For tamales, preventing cracking of the corn husk wrapping is the aim, so they're soaked in water to make them flexible 🌽

Infographic on Christmas crackers, showing the structure of silver fulminate and explaining how this friction-sensitive compound is placed on the ends of the two strips of card that form the cracker snap and detonates when the snap is pulled.

Infographic on tamales, made from a corn-based dough and steamed inside a corn husk. Nixtamalisation is the process of cooking and steeping corn kernels in an alkaline solution to degrade the outer layer of the corn kernel and soften the corn, making it easier to grind into flour.

Mulled wine and tangyuan for day 19 of #ChemAdvent!

Both wine and tangyuan contain long, chainlike molecules. In wine, it's the polymeric tannins that influence astringency and mouthfeel.

In tangyuan, made from glutinous rice flour, branched chains of amylopectin make the rice sticky

Infographic on mulled wine, showing the structures of two key flavour compenents: eugenol from cloves and cinnamaldehyde from cinnamon.

Infographic on tangyuan, Chinese dumplings made from glutinous rice flour. Low amylose content and higher amylopectin content makes glutinous rice sticky. Simplified structures of amylose and amylopectin are shown.

For the final #PeriodicGraphics of 2025, we look at C&EN's most-read stories of 2025: from lead in protein shakes, through underground hydrogen reserves, to chemistry peer review concerns.

Find links to each of the individual stories here: https://cen.acs.org/policy/publishing/Periodic-Graphics-most-read-stories-2025/103/web/2025/12

Infographic titled “C&EN Most-read stories of 2025,” listing the top 10 Chemical & Engineering News articles as of Nov. 5, 2025. Items are numbered 1–10 with brief summaries and icons. #1 reports that 1 in 5 chemists admitted adding errors to papers to get published. #2 explains why lead was found in protein powders. #3 covers concerns over NIH policy changes and alleged “banned words.” #4 features expert predictions for the 2025 Nobel Prize in Chemistry. #5 highlights how chemists with disabilities solve problems and advocate for inclusion. #6 discusses underground hydrogen as a climate solution. #7 presents C&EN’s Global Top 50 chemical firms for 2025. #8 reports Ethiopia having the highest scientific paper retraction rate. #9 describes bacteria converting plastic waste into paracetamol. #10 covers a study retracted over genetics ethics concerns. Branding and credits appear at the bottom.

Very contrasting smells for day 18 of #ChemAdvent!

Olibanic acid isomers contribute to the fragrance of Frankincense, traditionally associated with Christmas.

The aroma of hákarl, fermented Greenland shark, is a much less welcome one, dominated by ammonia and other pungent compounds.

Infographic on frankincense, showing the chemical structure of olibanic acid isomers, the key compounds responsible for the characteristic aroma of frankincense.

Infographic on harkal, fermented Greenland shark, traditionally eaten ad part of the mid-winter festival Þorrablót. It contains urea, trimethylamine oxide and ammonia, which dominate the pungent smell and taste of the fish.

If you brushed up on stinky skunk science with the previous edition of #PeriodicGraphics in C&EN, see how much you remember about the chemistry with this quiz!

For last-minute pre-test cramming, check the graphic here: https://cen.acs.org/biological-chemistry/Periodic-Graphics-makes-skunk-spray/103/web/2025/11
https://cen.acs.org/biological-chemistry/Quiz-much-know-chemistry-skunk/103/web/2025/12?sc=230901_cenrssfeed_eng_latestnewsrss_cen

It’s #Chemistree season! Here’s one I made back in 2016. The use of an upside-down pear-shaped flask as a tree topper was, in retrospect, an unfortunate choice…

Photo of a “Chemistree” – a Christmas tree decorated with chemistry glassware. The flasks are filled with tonic water (blue) and fluorescein solution (green/yellow) which both fluoresce under a UV light.

There's a whole graphic with more detail on the silver mirror reaction here: https://www.compoundchem.com/2017/09/06/silver-mirror/

Infographic titled "Making silver mirrors with chemistry". The infographic highlights the reagents: silver nitrate, ammonia, sodium hydroxide and dextrose. It also details the reaction which takes place, with the dextrose reducing Tollens' reagent to form a silver mirror.

Decorations and wrapping for day 17 of #ChemAdvent!

Baubles were traditionally silvered using the reduction of silver nitrate with glucose - a chemical test used in classrooms to detect aldehydes.

Wrapping paper and tape are both cellulose-based 🎁

Infographic on how baubles are silvered using silver nitrate solution, concentrated ammonia and glucose solution. Glucose reduces the silver ions to silver metal. The chemical structures of silver nitrate and glucose are shown.

Infographic on wrapping paper and tape. Both are based on cellulose, with tape also containing a pressure-sensitive acrylic or rubber-based adhesive. The structure of cellulose is shown.

Fermentation is the chemical connection for day 16 of #ChemAdvent: both Korean kimchi and Inuit kiviak take advantage of lactic acid bacteria fermenting carbohydrates and producing flavour compounds.

Infographic on kimchi, explaining how lactic acid bacteria produce key flavour compounds. A selection of flavour compounds are shown, including dimethyl trisulfide from garlic and onions, 2,3-butanedione which has a buttery flavour, and beta-phenyl acetate which has a rose/honey/sweet flavour.

Infographic on kiviak, an inuit delicacy eaten on special occasions, including Christmas. It's made by packing hundreds of little auks into a seal skin then fermenting them for 18 months. Lactic acid bateria ferment carbohydrates producing flavour compounds. A reaction scheme shows the lactic acid fermentation of glucose, starting with glucose, passing through 2-pyruvic acid and producing lactic acid.

With the current surge in flu cases, here's a useful graphic examining the different viruses responsible for colds and flu 🤒

I first made this one back in early 2020 – remember when we didn't all know what a coronavirus was?

Infographic titled “The viruses behind colds and flu.” It explains that adults get 2–5 colds per year and children 7–10, with symptoms peaking after 2–4 days and lasting about 7–10 days. Over 200 viruses cause colds. Rhinoviruses cause 30–50% of colds, coronaviruses 10–15%, influenza viruses 5–15%, and other viruses smaller percentages, with some unknown. Sizes of viruses are shown in nanometres, along with brief notes on transmission, mutation, vaccines, and treatment limits.

Looks like the US could finally be getting a new sunscreen molecule next year - 30 years since the last (via C&EN)
https://cen.acs.org/policy/Dec-12-Policy-Watch-FDA/103/web/2025/12?sc=230901_cenrssfeed_eng_latestnewsrss_cen

For day 15 of #ChemAdvent, the most tenuous connection so far.

Deep-fried caterpillars are a Christmas delicacy in South Africa, and tinsel... kind of looks like a giant sparkly festive caterpillar?

Yeah, it's a stretch.

Infographic on the chemical history of tinsel, from the use of shredded silver pre-1900, to the use of aluminium and lead foil, through to the polyvintyl chloride used today.

Infographic on deep-fried caterpullars, a Christmas delicacy in South Africa. The graphic compares the protein and iron content of the mopane worm (57% and 31-77 mg per 100 g respectively) to that of beef (22% and 6 mg per 100 g)

For day 14 of #ChemAdvent, we've got two fruity-themed graphics.

The first is on festive flamethrowers with orange peel and limonene 🍊 🔥

The other is on nastar, Indonesian pastry-based desserts filled with spiced pineapple jam 🍍

Infographic on orange peel flamethrowers, explaining how the presence of flammable D-limonene in orange peel oils makes it very flammable. The structure of D-limonene is shown and there's also a safety disclaimer.

Infographic on nastar, Indonesian pastry-based desserts filled with spiced pineapple jam. The structures of some key chemical contributors to pineapple flavour and aroma are shown; these include esters, such as ethyl-2-methylbutanoate and allyl hexanoate, and furaneol, also known as pineapple ketone.

St Lucia's Day links day 13 of #ChemAdvent: The saint is often depicted with a wreath of candles around her head, and in Sweden they celebrate with saffron buns (lussekatter)

Infographic showing how a blown-out candle can relight when a match is held in its smoke trail. The “smoke” is wax vapour that ignites. An example wax combustion equation is also shown.

Infographic about Swedish lussekatter saffron buns. Saffron gives colour via crocin and flavour from picrocrocin and safranal, the molecular structures of which are shown.

More vibrant anthocyanins link the graphics for day 12 of #ChemAdvent: they colour both cranberries and puto bumbong, steamed purple rice cakes eaten in the Phillipines at Christmas.

Infographic on cranberries antioxidants showing the chemical structure of quercetin. Quercetin is a polyphenol antioxidant in cranberry which may have positive health effects in humans. Suggestions that cranberry juice is an effective treatment for urinary tract infections have not been proven in research studies.

Infographic on puto bumbong, steamed purple rice cakes eaten in the Phillipines at Christmas. Anthocyanin pigments such as cyanidin 3-glucoside and peonidin 3-glucoside, the structures of which are shown in the graphic, give the rice its purple colour. The rice lightens when cooked as the bran (the outside of the rice grain) mixes with the endosperm (inside the rice grain).

Fascinating account of how analysis of Pompei’s building materials and tools gives us clues to the Roman empire’s concrete manufacturing methods: https://www.chemistryworld.com/news/romans-hot-recipe-for-self-healing-concrete-unravelled-in-pompeii/4022682.article
https://www.chemistryworld.com/news/romans-hot-recipe-for-self-healing-concrete-unravelled-in-pompeii/4022682.article

For day 11 of #ChemAdvent, we have a slightly tenuous medicinal link... 💊

Theobromine, found in holly berries (and chocolate), is prescribed for persistent cough in South Korea 🇰🇷

Opioids are well known for their painkilling abilities and appear in trace amounts in poppy seed bejgli from Hungary 🇭🇺

Infographic on holly and ivy. Holly berries contain bitter alkaloids such as theobromine, the structure of which is shown on the graphic. Poison ivy contains a the other compound depicted, urushiol, which can irritate the skin.

Infographic on bejgli, a sweet roll eaten in Hungary that is filled with poppy seeds, walnut paste or chestnut paste. The poppy seeds can contain trace amounts of opioid compounds such as morphine and codeine (the structures of which are provided in the graphic), which can cause opiate-positive urine test results.

This is a great dive into anthocyanins, tannins, and the oxidation chemistry of port in Chemistry World 🍷
https://www.chemistryworld.com/features/the-chemistry-of-port/4022483.article

Two poisonous plants for day 10 of #ChemAdvent! ☠️

Brazilian farofa is made from cassava flour, itself made from cassava roots which are soaked to remove toxic cyanogenic glycosides.

Mistletoe is much less likely to be eaten but is also toxic due to the presence of toxic peptides and tyramine.

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