Chemistry jokes get the best reactions

Today, 24th March, is Red Nose Day 2017 in the UK. I decided to see if I could collect some new chemistry jokes. There are some, of course, that we’ve all heard before – we might even say that all the best ones argon.

So, I promised to donate £10 if I got sent at least five new jokes. And I did! So I have! And here are my favourite five, in no particular order. Enjoy!

“I’ll tell you a joke about a tiny amount of iron for a small Fe.”@hullodave

“Chemistry Fact: There’s really no such thing as hydrogen. The inventor of the Periodic Table just needed a place to land a tiny helicopter.”@hullodave

“Why don’t they galvanise ships to stop corrosion? …That would make them zinc.”

“Do you know why everyone wants to work with bismuth? Because there’s no bismuth like showbismuth!” — @GriceChemistry

“I know a great long Justus Von Liebig joke but it needs condensing to get it on Twitter.” — 

If you’ve enjoyed these, if they’ve even so much as made you crack a little smile, please go and donate a couple of quid to Comic Relief. It’s a brilliant charity which helps people all over the world.

Donate here

Glow sticks or sparklers: which is riskier?

by Unknown artist,print,(circa 1605)

Remember, remember the 5th of November… (Image by Unknown artist, circa 1605)

It’s fireworks night in the UK – the day when we celebrate a small group of terrorists nearly managing to blow up the Houses of Parliament in 1605 by, er, setting fire to stuff. No, it makes perfect sense, honestly, because…. look, it’s fun, all right?

Anyway, logical or not, Brits light fireworks on this day to mark the occasion. Fireworks, of course, are dangerous things, and there’s been more than one petition to ban their sale to members of the general public because of safety concerns. It hasn’t happened yet, but public firework displays, rather than private ones at home, are more and more popular.

Which brings me to this snippet from a letter a friend of mine recently received.


In case you can’t read it, it says:

“NO SPARKLERS PLEASE – with so many children runni[ng] around, we believe it is too dangerous fro children to be [words missing] lighted sparklers around.
Last year we had a few incidents of children drinking the [words missing] glowsticks – please advise against this.”

Now there are some words missing here, but it’s fairly clear that sparklers are prohibited at this event, and it seems to be suggesting that children have managed to get into, and swallow, the contents of glowsticks. But they, by contrast, haven’t been banned. Indeed, parents are merely being asked to “advise” against it.


Does this seem like an appropriate response? Well, let’s see…

1024px-sparklers_moving_slow_shutter_speedWhat are these things? Let’s begin with sparklers. They’re hand-held fireworks, usually made of a stiff metal wire, about 20 cm long, the end of which is dipped in a thick mixture of metallic particles, fuel and an oxidising agent. The metal particles are most commonly magnesium and/or iron. The fuel usually involves charcoal, and the oxidiser is likely to be potassium nitrate. Sometimes metal salts are also added to produce pretty colours.

Sparklers are designed to burn hot and fast. The chemical-dipped end can reach temperatures between 1000-1600 oC, but the bit you hold doesn’t have time to heat up before the firework goes out (although gloves are still recommended). The sparks, likewise, are extremely hot but burn out in seconds. This makes sparklers relatively safe, if they’re held well way from the face and body, and if the hot end isn’t touched.

If. Every year there are injuries. Sparkler injuries aren’t recorded separately from other firework injuries in the UK, but the data we do have suggest we might be looking at a few thousand A&E admissions each year, and probably a lot more minor injuries which are treated at home.

Sparklers are most dangerous once they've gone out.

Sparklers are most dangerous after they’ve gone out.

The biggest danger comes from people, usually children, picking up ‘spent’ sparklers. The burny end takes a long time to cool down, but once the sparkles are finished and it’s stopped glowing it’s impossible to judge how hot it is just by looking.

The burns caused by picking up hot sparklers are undoubtedly very, very nasty, but they’re also relatively easy to avoid. Supply buckets of cold water, and drill everyone to put their spent sparklers into the buckets as soon as they go out. Hazard minimised. Well, assuming everyone follows instructions of course, which isn’t always a given. Other risks are people getting poked with hot sparkers – which can be avoided by insisting sparkler-users stand in a line, facing the same way, with plenty of space in front of them – and people lighting several sparklers at once and getting a flare. Again, fairly easily avoided in a public setting, where you can threaten and nag everyone about safety and keep an eye on what they’re doing.

Although I do understand the instinct to simply ban the potentially-dangerous thing, and thus remove the risk, the idea does worry me a little bit. I was born in the 70s and I grew up with fire. I remember the coal truck delivering coal to us and our neighbours. I was taught how to light a match at an early age, and cautioned not to play with them (and then I did, obviously, because in those days it was usual for kids to spend hours and hours entirely unsupervised – but fortunately I emerged unscathed). Pretty much everyone kept a supply of candles in a drawer, in case the lights went out. And bonfires were a semi-regular event – this being long before garden waste collections.

These days things are very different. It’s not unusual to meet a child who, by age 11, has never lit a match. If their home oven and hob are electric, they may never have seen a flame outside of yearly birthday cake candles. But so what? You may be thinking. Aren’t fewer burns and house fires a good thing?

Of course they are, but people who’ve never dealt with fire tend to panic when faced with it. If the only flame you’ve ever met is a birthday cake candle, your instinct might well be to blow when faced with something bigger. This can be disastrous – it can make the fire worse, and it can spread hot embers to other nearby flammable items.

I’m personally of the opinion that children ought to be taught to handle fire safely, how to safely extinguish a small fire, when to call in the experts, and not to disintegrate into hysterics the presence of anything warmer than a cup of tea. Sparklers, I think, can be part of that. Particularly if they’re used in a well-supervised setting, with plenty of safety measures and guidance on-hand. (As opposed to, say, picking them up for the first time at university with some drunk mates, setting fire to half a dozen at once and immediately dropping them.)

Now. Onto glowsticks. They’re pretty neat, aren’t they? We’ve already established that I’m quite old, and I remember these appearing in shops for the first time, sometime in the very early 90s, and being utterly mesmerised by that eerie, cold light.


Diphenyl oxalate (trademark name Cyalume)

They work thanks to two chemicals. Usually, these are hydrogen peroxide (H2O2 – also used to bleach hair, as a general disinfectant, and as the subject of a well-known punny joke involving two scientists in a bar) and another solution containing a phenyl oxalate ester and a fluorescent dye.

These two solutions are separated, with the hydrogen peroxide in a thin-walled, sealed glass vial which is floating in the mixture of ester and dye solution. The whole thing is then sealed in a tough, plastic coating. When you bend the glowstick the glass breaks, the chemicals mix, and a series of chemical reactions happen which ultimately produce light.

How Light Sticks work (from - click image for more)

How Light Sticks work (from – click image for more)

Which is all very well. Certainly nice and safe, you’d think. Glowsticks don’t get hot. The chemicals are all sealed in a tube. What could go wrong?

I thought that too, once. Until I gave some glowsticks to some teenagers and they, being teenagers, immediately ripped them apart. You see, it’s actually not that difficult to break the outer plastic coating, particularly on those thin glow sticks that are often used to make bracelets and necklaces. Scissors will do it easily, and teeth will also work, with a bit of determination.

How dangerous is that? Well… it’s almost impossible to get into a glowstick without activating it (the glass vial will break), so it’s less the reactants we need to worry about, more the products.

And those are? Firstly, carbon dioxide, which is no big deal. We breathe that in and out all the time. Then there’s some activated fluorescent dye. Now, these vary by colour and by manufacturer, but as a general rule they’re not something anyone should be drinking. Some fluorescent dyes are known to cause adverse reactions such as nausea and vomiting, and if someone turns out to be allergic to the dye the consequences could be serious. This is fairly unlikely, but still.

Another product of the chemical reactions is phenol, which is potentially very nasty stuff, and definitely not something anyone should be getting on their skin if they can avoid it, let alone drinking.

Inside every activated glowstick are fragments of broken glass.

Inside every activated glowstick are fragments of broken glass.

And then, of course, let’s not forget the broken glass. Inside every activated glowstick are fragments of broken glass – it’s how they’re designed to work. If you break the plastic coating, that glass is exposed. If someone drinks the solution inside a glow stick they could, potentially, swallow that glass. Do I need to spell out the fact that this would be a Bad Thing™?

The thing with hazards is that, sometimes, something that’s obviously risky actually ends up being pretty safe. Because people take care over it. They put safety precautions in place. They write risk assessments. They think.

Whereas something that everyone assumes is safe can actually be more dangerous, precisely because no one thinks about it. How many people know that glowsticks contain broken glass, for instance? Probably not the writer of that letter back there, else they might have used stronger language than “please advise against this.”

So glowsticks or sparklers? Personally, I’d have both. Light on a dark night, after all, is endlessly fascinating. But I’d make sure the sparkler users had buckets of water, cordons and someone to supervise. And glowstick users also ought to be supervised (at least by their parents), warned in the strongest terms not to attempt to break the plastic, and all efforts should be made to ensure that the pretty glowy things don’t fall into the hands of a child still young enough to immediately stuff everything into his or her mouth.

The most important thing about managing risks is not to eliminate every potentially hazardous thing, but rather to understand and plan for the dangers.

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Feet of clay? The science of statues

Concept art for the Terry Pratchett statue (c) Paul Kidby

Concept art for the Terry Pratchett statue (c) Paul Kidby

Yesterday we received the exciting news that a statue to commemorate Sir Terry Pratchett and his work has been approved by Salisbury City Council. Hurrah! So, even if we don’t quite manage to get octarine into the periodic table (and thus into every science textbook for ever more), it’s looking very likely that there will still be something permanent to help keep his memory alive.

But this got me thinking about everyday chemistry (who am I kidding, I’m always thinking about everyday chemistry!) and, in particular, bronze – the material from which the statue will be made.

Bronze, I hear you say, what’s that good for apart from, well, statues? And maybe bells? Is it really that interesting?

Well, let’s see. Bronze is an alloy. Alloys are mixtures that contain at least one metal, but they’re stranger than the word ‘mixture’ might perhaps suggest. Imagine combining, say, sand and stones. You still be able to see the sand. You could see the stones. You could, if you could be bothered to do it, separate them out again. And you’d expect the mixture to behave like, well, stony sand.

Alloys aren’t like this. Alloys (other well-known examples include steel, brass and that silver-coloured stuff dentists use for filling teeth) look, on all but the atomic level, like pure metals. They’re bendy and shiny, they make pleasing ringing sounds when you hit them and they’re good electrical conductors. And unlike more simple mixtures, they’re difficult (though not impossible) to separate back into their constituents.

Perhaps the most interesting this about alloys is that their properties are often very different to any of the elements that went into making them. Bronze, in particular, is harder than either tin or copper, and hence The Bronze Age is so historically significant. Copper is one of the few metals that can (just about) be found in its pure form, and so is one of the oldest elements we know, going back at least as far as 9000 BC. But while quite pretty to look at, copper isn’t ideal for making tools, being fairly soft and not great at keeping an edge. Bronze, on the other hand, is much more durable, and was therefore a much better choice for for building materials, armour and, of course, weapons. (War, what is it good for? Er, the development of new materials?)

Hephaestus was the God of fire and metalworking; according to legend he was lame.

Hephaestus was the God of metalworking. According to legend he was lame, could it have been because of exposure to arsenic fumes?

Today we (well, chemists anyway) think of bronze as being an alloy of tin and copper, but the earliest bronzes were made with arsenic, copper ores often being naturally contaminated with this element. Arsenical bronzes can be work-hardened, and the arsenic could, if the quantities were right, also produce a pleasing a silvery sheen on the finished object. Unfortunately, arsenic vaporises at below the melting point of bronze, producing poisonous fumes which attacked eyes, lungs and skin. We know now that it also causes peripheral neuropathy, which might be behind the historical legends of lame smiths, for example Hephaestus, the Greek God of smiths. Interestingly, the Greeks frequently placed small dwarf-like statues of Hephaestus near their hearths, and this is might be where the idea of dwarves as blacksmiths and metalworkers originates.

Tin bronze required a little more know-how (not to mention trade negotiations) than arsenical bronze, since tin very rarely turns up mixed with copper in nature. But it had several advantages. The tin fumes weren’t toxic and, if you knew what you were doing, the alloying process could be more easily controlled. The resulting alloy was also stronger and easier to cast.

teaspoon in mugOf course, as we all know, bronze ultimately gave way to iron. Bronze is actually harder than wrought iron, but iron was considerably easier to find and simpler to process into useful metal. Steel, which came later, ultimately combined superior strength with a relatively lower cost and, in the early 20th century, corrosion resistance. And that’s why the teaspoon sitting in my mug is made of stainless steel and not some other metal.

Bronze has a relatively limited number of uses today, being a heavy and expensive metal, but it is still used to make statues, where heaviness and costliness aren’t necessarily bad things (unless, of course, someone pinches the statue and melts it down – an unfortunately common occurrence with ancient works). It has the advantages of being ductile and extremely corrosion resistant; ideal for something that’s going to sit outside in all weathers. A little black copper oxide will form on its surface over time, and eventually green copper carbonate, but this is superficial and it’s a really long time before any fine details are lost. In addition, bronze’s hardness and ductility means that any pointy bits probably won’t snap off under the weight of the two-millionth pigeon.

So how are bronze statues made? For this I asked Paul Kidby, who designed the concept art for the statue. He told me that he sculpts in Chavant, which is an oil-based clay. It’s lighter than normal clay and, crucially, resists shrinking and cracking. He then sends his finished work away to be cast in bronze at a UK foundry, where they make a mould of his statue and from that, ultimately (skipping over multiple steps), a bronze copy. Bronze has another nifty property, in that it expands slightly just before it sets. This means it fills the finest details of moulds which produces a very precise finish. Conveniently, the metal shrinks again as it cools, making the mould easy to remove.

And just for completeness, Paul also told me that the base of the statue will most likely be polished granite, water jet cut with the design of the Discworld sitting on the back of Great A’Tuin. I can just imagine it – it’s going to be beautiful.

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