Warning – the dangers of PHMEA!

This is a warning about a chemical that, you’ll be amazed to hear, is found in homes all Surprised womanaround the country. Indeed, all over the world. You can readily buy it in shops.

The chemical is called polyhexamethylene adipamide, PHMEA for short (also known by a number of other names). It’s made from some really toxic substances: hexamethylenediamine and adipic acid. Hexamethylenediamine in particular is known to cause serious burns and severe skin irritation. And yet PHMEA turns up all over the place, even in clothing.

In fact it was shown on a popular TV program to be incredibly dangerous when used in clothing, particularly when combined with other common chemicals, and yet no one has done anything about it – it’s still on the shelves everywhere!

A steady increase in the production of PHMEA over recent years in Western countries correlates closely with a rise in obesity, leading some researchers to question whether they might be linked.

It has even been associated with crime, with criminals using it in a number of different ways. It can be used to incapacitate people as well as actually change their facial appearance! One criminal even blamed his entire crime spree on his exposure to it.

PHMEA exposure has been closely correlated with a number of different diseases, everything from chicken pox to cancer. Yes CANCER! One professional was quoted as saying, “I think it’s safe to assume that nearly 100% of people suffering from a disease have been in contact with [PHMEA] at some point”. It might even affect your brain directly. This is a true fact from the Apollo medical team.

It could even make men infertile, it’s been proven that PHMEA in clothing worn close to the body can reduce sperm count. And even give you smelly feet! One totally random member of the public said: “I found out that my socks are made of PHMEA – I had no idea. My feet were so stinky when when I took my shoes off my cat fainted!”. Another totally invented person said, “I developed a horrible sensitivity to PHMEA. I had terrible headaches and rashes. It’s all around you; it’s impossible to avoid. I’ve switched to tinfoil socks and now I’m sleeping much better. Mind you, the blisters are murder.”

Can you believe this dreadful substance is still so widely available? Most of you probably have it in your closets – check your labels now! Write to your local politician and demand better regulation of this dreadful chemical. SEND THIS WARNING TO ALL YOUR FRIENDS AND FAMILY NOW, if you don’t you’ll definitely get terrible athlete’s foot within 3 days. Don’t say I didn’t warn you. It’s also really important that you transfer $8008 into my Nigerian bank account.

Dr Kat Day suggests you pay attention to, well, the day. And would like to point out that she actually posted this the day AFTER the 31st March but due to some weird timey wimey stuff WordPress got the date wrong.

(P.S. Correlation is not causation.)

(P.P.S. the bit about hexamethylenediamine is true.)

The chemistry of chocolate

A lot of people believe there’s a deep religious significance to the holiday we’re enjoying right now.  Others argue it’s older than that: an ancient spring festival, celebrating the spring equinox, fertility and new growth.

funny-chocolate-Periodic-Table-chemistryBut every child knows what Easter is really all about.  Yes.  Chocolate.  Yummy, delicious chocolate.

So with that in mind, let’s talk a little about the chemistry of chocolate.  For it is very interesting stuff.  What’s in the lovely, creamy, sweet brown stuff?  And how do they get it to melt so perfectly in your mouth?  And does it really give you a happy high?

How do they get chocolate to melt so perfectly at body temperature?  There is more to this than you might imagine.  First of all you have to know something about crystals.  Most people, upon hearing the word crystals, think about clear, shiny things twinkling from from Katie Price’s latest wedding dress.  But in fact lots of substances form crystals, because a crystal is just a piece of any solid material that has regular shapes arranged symmetrically.  Crystals don’t have to be transparent.  Metals are crystalline.  Pure iodine forms rather pretty grey-silver crystals.  And, crucially, fat also crystallises.

In fact the fat in chocolate, cocoa butter, can crystallise in many different forms.  Only one of these is the lovely, hard, shiny one that is so nice and snappy at room temperature.  If you’ve ever cooked with chocolate, or indeed just left it in the car on a hot day by accident, you probably know that if you melt it and then just let it solidify again the result is dull-looking and crumbly.  Getting the right form of chocolate crystals to form is called tempering, and it’s a complicated business.  First the chocolate has to be melted at a high enough temperature to melt all the crystals.  Then it needs to be cooled to just the right temperature for the best crystals to grow, then agitated, then warmed up a tiny bit (but not too much), then cooled again.  There are other methods, but this is the one that’s used in the big chocolate factories.  Just ask the Oompa Loompas.

This ideal fat crystal form not only looks good and snaps nicely, it also melts at 34 oC.  Normal body temperature is actually around 36 oC, with the oft-quoted 37 oC actually being a tad on the high side.  Skin temperature, on the other hand (geddit?), is somewhere between 32-35 oC depending on how warm the environment is.  This means that chocolate will just about stay solid in your fingers if you don’t hold it too long, but put it in your mouth and the temperature is just right to melt it perfectly, releasing delicious sweetness, creamy fats and other chemicals that stimulate your tastebuds and give chocolate its flavour (craving your easter eggs yet?)

What about the other question: does chocolate really give you a ‘happy high’?  Well, it turns out there’s a whole cocktail of naturally-occurring bioactive chemicals (some people see ‘natural chemicals’ as a bit of an oxymoron and that’s ironic in a way, since the very brain that learned big words like oxymoron is actually stuffed full of natural chemicals that make it work) in chocolate.  Firstly, caffeine, otherwise known its less tongue-tripping name of 1,3,7-trimethylxanthine, but we’ll stick to caffeine.

We’re all familiar with caffeine from tea and coffee, and that drink that’s falsely advertised as giving you wings, but its presence in chocolate is sometimes forgotten.  It is of course a stimulant, exciting the central nervous system (it’s very excitable), boosting heart rate and contracting muscles.  It also acts on receptors in the brain and causes them to release pleasure-producing chemicals.  There isn’t a lot in chocolate though: it varies by type but even in the darkest of dark chocolate, there’s generally less caffeine than you’d get from even a single cup of tea.  Milk chocolate has even less and white chocolate has none at all.

But there’s more of another chemical, also a stimulant: theobromine.  This is interesting stuff.  It’s a heart stimulant and, like caffeine, a diuretic (it makes you wee).  More recently it’s use as a potential treatment for cancer tumours has been investigated.  There is roughly eight times more theobromine in chocolate than caffeine, but we metabolise it quickly so it doesn’t hang around in our bodies for long.  It’s less safe for animals: as any responsible dog owner will tell you, chocolate is very bad for dogs.  This is mostly due to the theobromine (the caffeine isn’t great either, but there’s not so much of that).  If your pooch gets into your Easter eggs, they could suffer nausea and vomiting, diarrhea, muscle tremors and, potentially, heart failure.  So keep your eggs out of reach.

It’s not just stimulants.  Chocolate also contains fatty acids called cannabinoids.  Guess what they’re similar to?  The clue is in the name… yes, their cousin is called tetrahydrocannabinol, and it’s found in the cannabis plant.  When cannabinoids hit the brain they make you feel relaxed and intoxicated.  And that’s not all, chocolate also contains phenethylamine, sometimes dubbed ‘the love drug’ because levels increase in the body when you’re feeling romantic.  Although there isn’t much and it’s metabolised too quickly to  have a significant effect.

So with this delicious swirly mixture of stimulants and suppressants, surely chocolate ought to be on some sort of controlled drug list?  Well, no.  All of these chemicals are present in relatively small amounts, and have a limited effect on the body (human bodies anyway).  People who suffer chocolate cravings aren’t satisfied by just swallowing capsules that contain the relevant chemical compounds, but eating white chocolate – which contains no cocoa solids and therefore none of the psychoactive ingredients – does the trick.  This suggests that the real reason we like chocolate is simply the same reason we like cream cakes: lots of sugar and fat – yummy!

So now you’ve stuffed your brain full of sciencey-stuff, go ahead and stuff your mouth with lots of yummy chocolate.  Happy Easter!

P.S. have you noticed that it’s kem-is-try but cho-ko-late?  This alliteration spoiling bit of linguistics is because the word chemistry derives from the word alchemy, which (probably, people argue over these things) comes from the ancient Egyptian name for Egypt – khem or khame, or khmi.  Hence al-khmi, ‘the Egyptian art’.  

Why is chemistry the forgotten science?

I recently had the privilege of talking to radio DJ and author Simon Mayo and he asked me what I thought of his book, Itch.  I said I loved it, and I really do.  (I have yet to read the sequel, Itch Rocks – released at the end of February – but it’s definitely on my list.)  I like Itch for many reasons.  I liked it because the lead character is a teenage boy who’s interested in science and actually finds arty subjects rather difficult, and yet is not a nerdy stereotype.  I like it because there was lots of action and an interesting story, coupled with just the right amount of research.  I liked it because the main female character is strong-willed, principled and absolutely doesn’t get involved in any sort of love triangle (this is not, to paraphrase my favourite film, ‘a kissing book’).  And most of all, I like it because it’s science fiction about chemistry.chemistry

As a chemist, it’s long seemed to me that, when it comes to the media and fiction, it’s the forgotten science. I can think of any number of famous science fiction works that hinge around physics and astronomy.  I can think of things based on biology.  I can even recall one or two that have both, for example Christian Cantrell’s Containment, a novel about a brilliant young scientist living on Venus and working on artificial photosynthesis.  But when it comes to chemistry I’m struggling.  Poisoning turns up in quite a few murder mysteries of course, as does forensics.  I suppose you could argue that some of the medical thrillers with plots that hinge around drugs might count.   Nanotechnology, as in Prey by Michael Crichton, is often thought of as a chemical field in the real world (TM), but thrillers on the subject tend to be less about matter on the atomic scale and more about improbably aggressive tiny robots.

It’s not just fiction.  In recent years there has been a noticeable increase in the amount of science programming, particularly on the BBC.  This is fabulous, but the large majority has been focused on physics and biology.  Radio 4’s The Infinite Monkey Cage often takes great glee in ignoring, and even ridiculing, chemical disciplines (I still listen to it mind you, in the manner of someone poking at a sore tooth).  The current run of BBC’s Horizon has exactly one episode (The Truth about Taste) that might be considered to have a chemistry focus.  At the end of last year Dara O Briain’s Science Club managed a whole series of six episodes without a single one on a chemical topic.  And so on and so on.  At least the most recent Royal Institution Christmas Lectures redressed the balance a bit, even if they were tucked away on BBC Four.  And as I posted recently, the quiz show Pointless seems to be quite fond of chemistry as a topic, so that’s something.

But why the general lack of chemistry?  Especially when you consider that the A-level is not only desirable but an essential requirement for so many degrees, including medicine, veterinary science, dentistry and pharmacy.  Whereas physics and, perhaps more surprisingly, biology aren’t. Since it’s so important you’d imagine there would be a bit more enthusiasm for the subject.

Is it linked to the background of the presenters?  Dara O Briain, in a previous life, studied mathematics and theoretical physics.  Professor Brian Cox, presenter of the Infinite Monkey Cage, is of course a physicist.  The only regular presenter I can think of with anything resembling a chemistry degree (actually biochemistry) is Liz Bonnin of Bang Goes the Theory.  But surely it isn’t impossible to find a chemist capable of presenting?  Peter Wothers did a cracking job with the Royal Institution lectures for starters.  And surely, surely, there’s room for the fabulously eccentric-looking Martyn Poliakoff somewhere?  (Please go and look at The Periodic Table of Videos if you have five minutes – it’s brilliant.)

But I’m not sure that’s the problem.  I imagine presenters largely talk about what they’re told to talk about.  No, I fear it might be simply the fact that chemistry is a bit, well, hard.

Early in my teaching career an exasperated A-level student complained, “miss, I thought chemistry was all setting fire to things and explosions and stuff, but it’s mostly just numbers and symbols”.  I’m afraid there’s some truth to this, particularly by the time we get to A-level chemistry, although I do like to set fire to things wherever possible (in a controlled manner of course – I’m not an arsonist, I swear).

I often joke with students that chemists use equations because we’re lazy.  For example, take this very simple experiment that you probably do every day if you have a gas cooker – it’s what happens when you set fire to methane:

CH4 + 2O2 –> CO2 + 2H2O

Now let’s write that in words: One molecule of methane, which contains one carbon atom bonded to four hydrogen atoms, reacts with exactly two molecules of diatomic oxygen irreversibly to produce exactly one molecule of carbon dioxide, which contains one atom of carbon bonded to two oxygen atoms, and two molecules of water, which contains two atoms of hydrogen bonded to an oxygen atom. 

Phew.  You can see why chemists prefer the equation.  Imagine if we had to write something like that every time we wanted to describe a reaction?  We’d never get anywhere.  Plus, once you understand them, the equations allow you to see similarities between different reactions that could be easily missed otherwise.  The symbols are essential.  But they’re also a bit, well, impenetrable.  A TV show with lots of chemical symbols would be as impossible to understand as one presented in French for many, and rather more difficult to subtitle.

So yes, it can look a bit scary.  But it’s not impossible.  After all you need advanced mathematics to understand physics in depth, but plenty of physics programmes explain their subject matter without even hinting at the dreaded doublet of differentiation and integration.  A good chemist can make the subject accessible with a bit of creativity.

It’s not as if there’s not lots of interesting material (pun entirely intended).  Chemistry is the science behind explosives, cooking, medicines, bubbles, pigments and poisons.  It has a fascinating history, populated with characters such as Fritz Haber, the father of chemical warfare who also solved the problem of global food security, Glenn Seaborg who discovered ten (ten!) of those elements that loiter at the bottom of the periodic table, Henry Cavendish – discoverer of hydrogen and famously so shy he was unable to talk to women, Antoine Lavoisier, tax collector, traitor and the person who named both oxygen and hydrogen and let’s not forget Carl Wilhelm Scheele, discoverer of some of the most dangerous substances known to man.  There are endless stories that could be told, from the legal case of the Carbolic Smoke Ball to Kekule’s dreams of snakes eating their own tails, to bizarre medical practices such as antimony pills and the mystery of the Bradford Sweets poisoning.

If Simon Mayo can write a series of highly successful novels featuring chemistry aimed at young adults, it must surely be possible to make a few more shows on the topic.  So writers, editors and producters I beseech you not to be scared of chemistry.  Find yourself someone with a bit of knowledge in the area and get on with it.  For whatever chemistry is, it’s far from boring.

Do you know of any chemistry science fiction I’ve missed?  Have you got any favourite chemical stories that you think should be on telly?  Please tell me about them!

My Pointless addiction

I love the TV show Pointless (5:15pm weekdays on BBC1, and I didn’t have to look that up).  I am an unashamed addict.  For those that have never watched, they give 100 members of the public 100 seconds to answer questions, and the aim of the contestants is to name the most obscure answer provided in particular category, in other words the one the fewest people answered correctly.  As I write, the current topic is TV Armstrong 4elements of the periodic table.  They use the periodic table quite a bit – they must have a chemist in their team of research elves (it’s sort of implied that the lovely Richard Osman makes up all the questions, but I’ve always assumed he has at least some help).

Naturally I can name all the answers in this round.  They are: sulfur, copper, mercury, sodium, fluorine, nitrogen and barium.  Yes all right, I’m showing off now.  I reckon nitrogen might be the lowest, since its clue is about its boiling point.  We’ll see in a bit…

I’m actually rather comforted by some of the high scores.  34 people out of 100 recognised sodium and 39 barium.  54 got copper and 80 mercury.  There is hope for the nation after all.

Ah, it turns out that fewer people knew it was a compound of fluorine in toothpaste.  Heston Blumenthal and his habit of chucking liquid nitrogen around has a lot to answer for.  It was close though, the second lowest score.

Now for the next round.  Now I’m helped here by the fact that they’ve included atomic numbers, else I’m not sure I’d have got the one referring to album sales.  I’m vaguely aware that gold and platinum albums are possible (and silver?), but I’m clueless as to the sales numbers required.  Ok: oxygen, zinc, platinum, magnesium, bromine, radon and carbon.  I reckon the lowest is going to be… um… well probably platinum.

And while I wait, thank you Richard for stating the correct spelling of sulfur in two episodes now.  I’m always arguing with people about that.

Hmm, I couldn’t have been more wrong.  Platinum was in fact the second highest answer on the board after oxygen.  As Alexander Armstrong pointed out, I suppose that’s really about your knowledge of the music business (an area in which I am pitifully uninformed).  The lowest score was bromine.  I should have realised.

Oh dear the next round is on English Football.  I’d be straight out.

Women who ignored the limits: five famous female chemists

Browsing a popular newspaper site the other day I came across this very funny article by Dean Burnett, inspired by the brilliant Harry Enfield ‘Women, know your limits!’ sketch of a few years ago in which a woman dares to offer a dangerous opinion of her own.  In the sketch, filmed in the style of a 40’s black and white public information film, Mr Enfield claims that over-education leads to ugliness, premature ageing and beard growth, and beseeches women to stick to what they know best, namely, fluffy kittens.  know your limits

All very funny and yet… ask anyone to name some famous scientists and I bet you anything that at least the first five names they come up with are men.  Perhaps this is to be expected, after all the scientific method has been kicking around for ooh, well, it’s debatable, but at least 1000 years if not more.  Whereas the ludicrous idea that most women might be capable of learning about tricky things like numbers and and stuff has only been widely accepted, in this country in any case, for a few decades or so.

So to balance the books a bit, here’s my list of five famous(ish) women chemists, none of whom had beards (as far as I can tell).  Absorb and learn.  If nothing else, should the topic of scientists ever come up on the TV quiz show Pointless I can guarantee most of these will be down there in single figures, if not actually pointless.

Cleopatra the Alchemist (dates unknown)
Not the same person as Cleopatra VII, this one lived (probably) in the 3rd or 4th century.  The title Cleopatra the Alchemist is a pseudonym and her real name has been lost.  She was thought to be one of only four women who knew how to make the mythical philosopher’s stone (yes, just like in Harry Potter.  Well sort of) and, perhaps more scientifically, her work also contained several descriptions and drawings of the technical process of furnaces.  She’s also sometimes credited with the invention of an early type of distillation apparatus.  Without this useful chemical technique, we wouldn’t have petrol, plastics or, indeed, vodka.  Cheers!

Marie Curie (1867-1934)
The Polish Madame Marie Curie is most famous for her work on radioactivity and is often thought of as more of a physicist.   However she definitely earned her chemical chops for discovering two (count ’em, two) whole new elements: polonium (Po) and radium (Ra).  She painstakingly managed to isolate about 0.1 g of radium chloride from 1 ton (907185 g) of the mineral pitchblende.  Now that’s patience.  In 1948 the element curium (Cm) was named in her, and her husband Pierre’s, honour.

Elizabeth Arden (1884-1966)
A famous name, if not one we necessarily associate with science, she was born Florence Nightingale Graham and changed her name in 1909.  Although not formally educated as such, she counts as a chemist for formulating, as well as manufacturing and marketing, her cosmetic products.  She pioneered the idea that cosmetics could and should be scientifically formulated, a concept that many other companies subsequently copied.  She did wear an awful lot of pink, but nobody’s perfect.

Rosalind Franklin (1920-1958)
Who discovered the structure of DNA? Wasn’t that Watson and Crick? Actually it was x-ray crystallographer Rosalind Franklin who produced the first images of deoxyribonucleic acid, and Watson and Crick even publicly admitted to using her data to develop their hypothesis.  Sadly Franklin was a cautious scientist and her work, based on experimental results, was published after their theoretical paper.  Subsequently she’s often forgotten about, particularly because, as she died in 1958 and the rules forbid posthumous nominations, she was never included included in the Nobel Prize awarded to Crick, Watson and Wilkins in 1962.  Don’t hide your light girls.

Anna Jane Harrison (1912-1998)
Harrison, who unlike many historical chemists (when you spend your days messing about with substances that so often turn out to be toxic, you’re invariably in danger of shuffling off this mortal coil earlier than most) managed to live until the ripe old age of 86, was an American organic chemist and the first female president of the American Chemical Society.  She was also the recipient of twenty honorary degrees, none of which were bought from dodgy internet sites.  She worked on toxic smoke during the second world war, and also contributed to research on ultraviolet light.

Sadly, none of these ladies are alive today.  Can you think of any other female chemists who’ve made important discoveries?  Tell me about her…

Jellyfish and wee – should you rely on the movies for first aid advice?

Hello and welcome to ‘the chronicle flask’, a blog of interesting chemical bits and pieces. Jumping right in, we begin with a tale of jellyfish, wee and wittertainment.  Here goes…

ImageLast week I was listening to the Kermode and Mayo ‘wittertainment‘ film podcast in which the esteemed film critic Mark Kermode was discussing the film The Paperboy.  There’s a scene in this film in which Nicole Kidman’s character wees (urinates, for the benefit of any non-Brits) on Zac Efron‘s jellyfish sting. It’s an idea that’s been used before, famously in an episode of Friends, and the question arose: does this actually work?  For those that aren’t aware, Simon Mayo is also an author of the rather wonderful Itch series of books, which hinge around a character with an interest in chemistry, and he wanted to know what the chemical equation might be for the wee + jellyfish venom reaction.  So, being a chemist and a big fan of the show, I fired off an email on this very subject.  Here it is:


First of all a quick reminder of the pH scale: it goes from 0-14 where 0 is very, very acidic (think battery acid) and 14 is very, very alkaline (think drain cleaner), and 7 is neutral (think water).

I mention this because acids neutralise alkalis, and vice versa.  If you mix exactly the right amount of acid with the right amount of alkali you get just water and salts.

Since you asked for an equation the general one is:

acid + alkali –> salt + water

Human urine is, actually, about pH 7, i.e. the same as plain water.  People often think it’s alkaline because they have the idea there’s ammonia in it, but there isn’t and it’s not (well not usually).  It varies a bit from 4.6-8, and if anything it tends to be a tiny bit acidic.  If you have a urinary infection it can become more acidic, but we’ll assume for our purposes that Nicole Kidman didn’t.

Jellyfish venom not surprisingly varies by species.  I’m relying on the internet here as I’m not a zoologist, and it seems that there are lots of different varieties of jellyfish in Florida, so the sting could be anything.  But as far as I can work out, they tend to be alkaline (greater than 7).

So if jellyfish venom is slightly alkaline, and human urine is slightly acidic, one MIGHT neutralise the other, and this is probably what lies behind this.  Obviously TV shows and films like this endlessly perpetrate the idea, so it sticks.  In truth this ‘remedy’ is unlikely to do anything much though.

In fact it might actually make it worse.  The proper, official medical advice is to rinse the area with salty seawater, because that apparently deactivates the stinging cells whereas plain water (and urine is closer to plain water than seawater) makes it worse – I imagine this is to do with osmosis, but that’s a lesson for another day – try and remove the stinging cells by scraping the skin with a credit card and, obviously, seek medical attention.

Whatever you do don’t try battery acid.  That’d be really bad.


I was then contacted by the editor of the show, and they actually invited me on to explain this as a special guest.  This, as you might imagine, made my week – I don’t think they’ve ever had a non-film guest on the show before.  If you’d like to hear it, you can download it here.  The shows used to only be available for about a week but they now seem to be hanging around a bit longer (hurrah!).

Now since this is supposed to be a chemistry blog, I have a few more musings on the topic of animal stings.  Jellyfish aren’t the only creatures to have this sort of defence mechanism of course, and probably more familiar to us here in the UK are the humble bee and wasp.  Bee stings are acidic, whereas wasp stings are alkaline.  So can you treat them with household acids or alkalis?  I think, to my shame, that I may even have suggested vinegar as a treatment for wasp stings myself in the past.

Now that I actually think about this for more than 30 seconds I realise that this is very unlikely to be effective.  First of all, wasp venom is complicated stuff.  After all it’s not as if the wasp is injecting a few drops of pure alkali into your arm.  No, wasp venom contains, amongst other things, enzymes which help to break down cell membranes and a chemical to reduce blood flow called norepinephrine, which is why the sting hurts for ages and doesn’t immediately get flushed away by your bloodstream.  The sting itself is a tiny amount of fluid, and only a minute amount of acid would be required to neutralise any alkali present.  So will sloshing an unknown quantity of an unknown concentration of acetic acid (the acid in vinegar, also known as ethanoic acid) actually achieve anything?  Especially considering that the sting is injected under the skin, whereas you’re dribbling the contents of your kitchen cupboard on the surface?  Very unlikely.  Chances are you’ll just irritate your skin even more.

Of course there is the placebo effect to consider.  Doing something, anything, rather than just dancing around yelping in pain will probably make you feel better.  And rubbing your skin usually makes minor injuries hurt a bit less.  But chemically?  Nah.

So in short, if you get stung it’s probably more effective to reach for the paracetamol rather than the condiments.