Element Tales: A Meandering Stroll Around 118 Elements

On 7th Feb this year Mark Lorch, a chemist and science communicator at the University of Hull, had the idea to start an element association game. Could a determined bunch of Twitter chemists find a path through all 118 elements of the periodic table in honour of Periodic Table Day and the International Year of the Periodic Table?

It turned out that they could! #ElementTales started with mendelevium, and meandered — avoiding a few forks — all the way to gadolinium. Some of the links are funny, some are tenuous, and a lot refer to fascinating bits of chemistry trivia.

It seemed a shame not to preserve the final thread somehow. Each of the entries below is headed with a link to the original tweet — just in case you’d like to find, and follow, the thread yourself.

Without further ado, we present to you…

A meandering stroll around 118 elements

@Mark_Lorch
Hey folks! Who’s up for an element association game for in . The rules: I’ll start with an element, you reply with a story/factoid that links it to another element and so on… No repeats!

An atom of Mendelevium, atomic number 101 (from Wikimedia Commons)

@Mark_Lorch
It’s only fitting to start with number 101 Mendelevium

@Sciencenotscary
Mendeleev designed the first periodic table, which contains every other element, including <spins random number generator> #52, tellurium <blink> I swear that was random.

@Stare_at_Air
That feels a bit like cheating! But tellurium was first discovered in gold ore from Zlatna (a Romanian town named after the Slavic term for gold).

@RyeSci
Gold is one of those lovely elements known to the ancients with a symbol accordingly, Au. My favourite of those is Mercury, Hg from Hydrargyrium or liquid silver Hg.

@chronicleflask
Mercury has a v low MP because its electronic config, [Xe] 5d10 6s2, has all full shells — so it doesn’t form the +ve metal ions & delocalised electrons bonding system as other metals. Also quantum. Zn (zinc) has a low MP for the same reason.
(Side note: see this article for more info on mercury’s liquidity https://www.chemistryworld.com/news/relativity-behind-mercurys-liquidity/6297.article)

@allisontau
Zinc is element 30. Zinc rhymes with sink. If your kitchen sink is broken you call a plumber. Plumbers are called plumbers after plumbum, the Latin word for the element lead (Pb), because the Romans used lead to make pipes.

@Mark_Lorch
Lead in Greek is μολυβδος – Molyvdos which gives use the name of element 42, molybdenum.

bacteria@chronicleflask
Molybdenum-containing enzymes are found in bacteria: the simplest and oldest of the living organisms. Living organisms on planet Earth have carbon-based biology. (Time for some non-metals, I thought!)

@Stare_at_Air
This could be taken in so many directions based on carbon‘s chemistry, but I’ll ruin it — carbon reminds me of “Carboniferous”, which sounds like it should have something to do with iron (it doesn’t).

@sciencenotscary
Iron is in the same column of the periodic table as ruthenium, which usually means it should have similar reactivity and chemical behaviour, but it turns out iron is actually completely useless as a catalyst and will not get you a PhD.

@SuperScienceGrl
I’ve had a couple of people mistake my cat’s name, RuPhos, for something to do with ruthenium – it really isn’t, it’s a phosphorus ligand.

@Mark_Lorch
Phosphorus was first extracted from urine by Hennig Brandt in 1669. Later is was discovered that bone is calcium phosphate, which made for a ready supply to feed the match industry.

@David_S_Bristol
Calcium and phosphorous combine in bone along with a substantial amount of magnesium. ~60% of magnesium in the body is in bone. It is essential for a healthy skeleton and reduced magnesium is linked to osteoporosis.

@Stare_at_Air
Magnesium is a key component of Grignard reagents. Grignard shared his Nobel Prize with Sabatier, who in turn received it for his method of hydrogenating organic compounds. Hydrogen.

@drdelusional
Hydrogen, the lightest element, forms the majority of the mass of the Universe. This odorless and tasteless gas combines with Fluorine to result in hydrogen fluoride, a highly reactive acid.
(Side note: corrosive, not (especially) reactive.)

@WildCation
Electronegativity generally increases from left to right across a period, and generally decreases from top to bottom. Fluorine is the most electronegative element on the Pauling electronegativity scale. The LEAST electronegative element is (probably) caesium.

@chronicleflask
Ooh, ooh: Robert Bunsen (he of the burner) and Gustav Kirchhoff discovered two alkali metals, cesium and rubidium, in 1860.

@Stare_at_Air
Rubidium is one of several elements named after a colour (in this case the red lines seen in the emission spectrum), but chromium is associated with so many different colours it’s just named after the Greek word for colour, χρῶμα.

@Mark_Lorch
Amongst the Terracotta warriors were found what appears to be chrome (chromium) plated bronze swords. The alloy was mostly copper and tin, but also contained magnesium, nickel and cobalt.

@sumants
Cobalt is named from ‘kobold’, German for ‘goblin’. This comes from German miners – who were harvesting (cobalt) blue pigments – naming ores ‘goblin ores’ due to the effects of arsenic poisoning when the ores were smelted.

@WildCation
The use of Scheele’s Green, a popular green arsenic-based pigment, caused poisonings in the 19th century from its use in wallpaper, candles, even food. Similarly, in the 1920s, the “Radium Girls” developed cancer from painting watch faces with radium-based pigment.

@Mark_Lorch
Radium was discovered by Marie and Pierre Curie when they extracted it from Uraninite ore. From the same ore they extracted another element which they initially called radium-F. Later Marie renamed if after her home country – Poland. Giving us … Polonium.

@Stare_at_Air
I think the f-block is feeling a bit unloved, so let’s go from the elements that the Curies discovered (Polonium) to the one named after them. Curium.

@ndbrning
Curium is (possibly) the heaviest naturally occurring element (see here: https://www.nature.com/articles/s41557-018-0190-9). The other possible candidate is plutonium.

@Stare_at_Air
Plutonium was indirectly named by a child (the name Pluto for the planet was suggested by an 11-year-old girl). The only other element named by a child is neon, suggested by Ramsay’s son.

@Mark_Lorch
William Ramsay (neon) was also the first person to isolate helium. Prior to this is was known to exist from the spectra of the Sun. Hence the element’s name from Helios… Helium.

@DrMLHarris
Inhaling helium makes your voice squeaky. What happens if you inhale xenon? Researchers at a prestigious US lab decided to find out. Turns out, “heavier than air”=”too heavy for lungs to expel”. The experimenter’s life was saved when he stood on his head.
(Side note: watch what happened when Dr Bunhead of Brainiac tried the same thing.)

@FioraAeterna
Xenon is a really unusual element. In fact, it’s the only pure element that is also a general anesthetic! Yet it’s an unreactive noble gas. Weird, huh? For weird reasons, both Xenon and Argon are now on the anti-doping banned chemicals list.

@Stare_at_Air
People are often surprised to find that the third most abundant gas in the Earth’s atmosphere is Argon. Perhaps similarly surprising is that the third most abundant element in the universe as a whole (at least as far as we know) is oxygen.

@Mark_Lorch
Oxygen is a paramagnetic. If you condense some (it’s a beautiful pale blue liquid) and then place a neodymium magnet above the surface the oxygen jumps up onto the magnet. https://www.youtube.com/watch?v=bQKVt27SUR0&feature=youtu.be&t=91

@sumants
Neodymium was originally mined as a twinned material known as didymium. Carl Auer von Welsbach fractionally distilled didymium to isolate neodymium (new twin) and the other “green twin”, praesodymium.

@Stare_at_Air
“Green twin” in Greek (πράσινος and δίδυμος) is the base for the name of praseodymium — meanwhile “green twig” in Greek (θαλλός) is the base for the name of thallium, after the bright green spectral line used to identify it.

@sumants
Thallium was extremely popular as a poison in the early 20th century, but it’s mostly banned today. As a rat poison, it worked because it inhibited proteins that contained cysteine, an amino acid that contains… Sulphur.

@ndbrning
Sulfur
is responsible for the tarnishing of silver. The black tarnish is silver sulfide, caused by the metal’s reaction with small amounts of hydrogen sulfide in the air.

@Mark_Lorch
To clean your silver spoons put them in hot water with bicarb of soda & aluminium foil. The bicarb removes the aluminium oxide layer. This leaves the aluminium free to react with the silver sulfide, giving aluminium sulfide & clean silver.

@Stare_at_Air
What is still often called “tin foil” is nowadays almost always made from alumin(i)um. But it used to be made exclusively from tin until the early 20th century (first Al foil came around in 1910, but it took a few decades for it to replace Sn foil).

@sciencenotscary
Tin has two allotropes, a metallic one and a powder. It converts to the powder at Russian-winter temperatures. Napoleon’s troops had tin buttons on their jackets, which then wouldn’t close, and they died of exposure. Russia is the home of Dubna. Dubnium.

@ndbrning
One of the originally proposed names for Dubnium was Nielsbohrium, after Danish nuclear physicist Niels Bohr. Though this proposal wasn’t accepted, Bohr did eventually get an element named after him: element 107, bohrium.

@sumants
One of the two groups to have claimed discovery of bohrium in 1976 was led by Soviet scientist Yuri Oganessian, in whose honour we now have… Oganesson.

@robcarrphoto
Only 5 to 6 atoms of Oganesson have ever been detected. Originally thought to be a gas, computational chemistry revealed it would be a solid due to relativistic effects. Special & General Relativity were discovered by Albert Einstein, for whom Einsteinium was named.

@Stare_at_Air
Einstein (Einsteinium) famously developed his theory of relativity while working at the patent office. The first element to be patented was Americium.

@Mark_Lorch
Americium is created by bombarding uranium or plutonium with neutrons. It was first made by Seaborg (from Berkeley) in 1944 as part of the Manhattan project. Soooo many ways to go from here, but I’m going with… Seaborgium.

@Stare_at_Air
Shortly after the ACS announced 106 to be Sg (Seaborgium) in 1994, resolved not to allow names based on living people. Until it gave way about a year later, the IUPAC name for 106 was rutherfordium. In 1997, this name was instead assigned to element 104… Rutherfordium.

@chronicleflask
Rutherfordium was named after Ernest Rutherford, prob. most famous for the Rutherford atomic model developed after Geiger & Marsden’s gold foil expt. But he also carried out research into nuclear reaction bet. nitrogen & alpha particles.

@sciencenotscary
Nitrogen is usually thought of as being mostly inert an unreactive, until you make it an azide. Sodium azide is what inflates your car’s airbag in time to stop your head smacking the steering wheel.

@Mark_Lorch
After my grandpa died I helped clear his flat, over the years he had stashed various chemicals including 1/2kg of Na (sodium), KCN & conc HCl. To this day I shudder to think what might have been if I hadn’t been there to stop my family chucking it all down the sink. Chlorine.
(Side note: read more about that story here http://www.chemistry-blog.com/2013/04/18/chemical-nostalgia-my-grandfathers-lethal-legacy/)

@robcarrphoto
In organic chemistry lab, we used a lot of HCl (chlorine) of organic reactions, making salts, etc. But when I think of the Chemistry building, I think of bromine. The building smelled like bromine. The set of Beilstein books smelled like bromine.

@Mark_Lorch
Two of the elements stink. Bromine means “stench” and osmium means “smells”.

@ndbrning
Osmium is used in an alloy to make the tips of fountain pens hard and wear-resistant. In the past, iridium was used for this purpose, and sometimes the tipping material is still referred to as ‘iridium’ despite the element’s absence.

@Stare_at_Air
Not only was iridium discovered in the residue from trying to dissolve (impure) platinum, but Pt-Ir alloys are very useful, being both hard and chemically stable. The prototype kilogram is made of Pt-Ir, though a new definition of the kg comes in in May.

@sumants
The Pt-Ir (platinum) alloy was also used to make the prototype meter bar, which was replaced by a measure based on an electron transition within a Kr-86 atom. Krypton.

@sumants
While we’re going on about defining lengths, the Kr-86 (krypton) standard also redefined the ångström as 0.1nm, making obsolete the previous reference based on the spectral line of… cadmium.

@ndbrning
Cadmium is used in nickel-cadmium (Ni-Cd) rechargeable AA batteries. Due to cadmium’s toxicity, their sale has been banned in the EU for most purposes since 2006. They’ve been supplanted by another type of nickel-based battery, nickel metal hydride (NiMH).

@drdelusional
Breithauptite or NiSb (nickel) is a pale copper red colored mineral named after Johann Friedrich August Breithaupt, a Saxon Mineralogist. Antimony.

@chronicleflask
Antimony compounds have been powdered for use in medicine and cosmetics for thousands of years, often known by the Arabic name, kohl. Titanium dioxide is another common additive in makeup and sunscreens.

@Mark_Lorch
Titanium
 causes no immune response, making it an ideal material for implants. However it does slowly corrode in the body. A ceramic made of zirconia (zirconium dioxide) doesn’t suffer from this problem and is now commonly used for dental implants. Zirconium.

@drdelusional
Zirconium alloys are mainly used in nuclear reactors, however these alloys should not contain Hafnium.
(Side note: see this article for more info as to why http://www.iloencyclopaedia.org/part-ix-21851/metals-chemical-properties-and-toxicity/63/zirconium-and-hafnium)

@Stare_at_Air
Hafnium is one of two elements whose name is based on the Latin form of a Scandinavian capital — Hafnia is Copenhagen, while Holmia is Stockholm. Holmium.

@sumants
While working with erbia (grounds for a whole fascinating fork!), Per Cleve isolated two oxides, one which he called holmia (holmium oxide), and the other, thulia, which was identified as thulium oxide. Thulium.

@sumants
Thulium is commonly found in a mineral known as gadolinite, which is named after Johan Gadolin. While it doesn’t have much gadolinium in it, Gadolin wrongly thought a white metal he found in it was aluminium, and not… Beryllium.

@ndbrning
Beryllium is found in the mineral beryl, which emerald and aquamarine are precious forms of. One of the rarest varieties, red beryl, gets its colour from the presence of small amounts of manganese.

@chronicleflask
Manganese is used in REDOX titrations; the colour change from VII (dark purple) to II (pale pink) is very obvious. It’s commonly used to determine the amount of iron present. Another species that turns up in REDOX titrations is iodine/iodide.

@sciencenotscary
Iodine can occur in the form HIO4, periodic acid, which looks like the word for the table we’re talking about but is actually per-iodic. A metallic compound with a very similar electronic structure is perhenate, based on rhenium.

@ndbrning
Rhenium was (possibly) first discovered by Masataka Ogawa in 1908, though he thought he’d discovered element 43, technetium (which wasn’t actually discovered until 1937).

@sciencenotscary
One of only two cis-uranic elements with no stable isotopes, it (technetium) had to be synthesised to be discovered (hence the name). The other one is protactinium.

@ndbrning
The first long-lived isotope of protactinium was discovered by Otto Hahn and Lise Meitner in 1917. 80 years later, in 1997, Meitner became one of only 16 scientists to have an element named after them… Meitnerium.

@MrVanOosterhout
Meitnerium was first produced by German nuclear researchers in 1982, who bombarded a bismuth sample with iron ions. A week of bombardment produced a single meitnerium ion, which lasted all of five milliseconds before decaying.

@chronicleflask
The name bismuth dates from around the 1660s, and it’s unclear where it came from, but maybe from Old High German hwiz (“white”). Like water, liquid bismuth is denser than solid, a characteristic it also shares with the element germanium.

@Stare_at_Air
The name germanium proved controversial, sounding like geranium. Jokingly, angularium was proposed, hiding a translated form of the discoverer’s name (Winkler). Lecoq denied doing something similar when naming gallium (Gaul, but also gallus = rooster).

@drdelusional
Gallium is a low melting solid (melting point ~30°C) and it combines with selenium to form Gallium Selenide which finds applications in nonlinear optics.

@sumants
Selenium was identified by Berzelius and Gahn from pyrite found in the Falun mine in Sweden, which is one of the world’s largest repositories of Copper.

@Mark_Lorch
Eight elements were first isolated from rocks quarried in a the small village of Ytterby in Sweden (same country as copper mine). Four of those elements are named in tribute to the village (ytterbium, erbium, terbium, yttrium)… Ytterbium.

@Stare_at_Air
Near the Ytterby (ytterbium) mine is this sign, discussing Gadolin’s work and the elements found there. It talks about a “tung, svart sprängsten” (in this case the black, heavy gadolinite), but it just reminded me of the origin of the name tungsten!

@drdelusional
A compound of Tungsten, Potassium tungsten oxide, is used in solar energy and water treatment applications… Potassium.

@DrMLHarris
Potassium comes in both fermionic and bosonic isotopes, making it ideal for the study of both Bose-Einstein condensation and cold Fermi gases. Lithium also has this property.

@DrMLHarris
The first molecular Bose-Einstein condensate was created in 2003 by pairing up atoms of fermionic lithium-6 (lithium) to make bosonic Li2 molecules. Fermions are, of course, named after the physicist Enrico Fermi, who also has an element named after him... Fermium.

@sumants
Fermium was discovered in the fallout from a nuclear test, as was einsteinium when some filter papers were exposed to the same fallout. The work happened at the University of California, Berkeley, after which place we have… Berkelium.

@sumants
Berkelium is now synthesized mainly in the Oak Ridge National Laboratory in Tennessee, after which state, we have Element 117… Tennessine.

@DrMLHarris
Tennessine itself was synthesized at the Joint Institute for Nuclear Research in Dubna, Russia. The many contributions of this institute to the Periodic Table were recognized in the name of Element 115… Moscovium.

@sumants
Moscovium naturally underwent alpha emission and created… Nihonium.

DrMLHarris
Nihonium was named after the country where it was discovered, Japan. The discoverers expressed hope that this honour would help the country’s trust in science recover after the meltdown of the reactor at Fukushima, which uses uranium as fuel.

@sumants
Uranium, of course, is named after the planet Uranus. It probably makes sense, then, that its neighbour would be named after the planet’s neighbour, Neptune… Neptunium.

@Stare_at_Air
Despite many previous false claims of having produced element 93, including by Fermi, neptunium was first produced by McMillan and Abelson, at Berkeley Lab (yes, Berkeley again, of course), based in the state of California… Californium.

@sumants
Californium was first synthesized at the Lawrence Berkeley NL, which is named after Ernest Lawrence, after whom we have… Lawrencium.

@Mark_Lorch
Lawrencium is the final member of the actinides. Although it is arguably a member of group 3 along with scandium, yttrium, and lutetium… Scandium.

@sumants
When Mendeleev placed scandium in his periodic table, he had previously predicted its existence, which Per Cleve eventually confirmed. He named it eka-boron, since it would have been similar in its properties to… Boron.

@sumants
Borosil is a brand name that makes borosilicate glass, which is made from a compound oxide of boron and… Silicon.

@DrMLHarris
The A3B group of compounds (A=transition metal, B=anything) wasn’t considered particularly interesting until vanadium silicide, V3Si, (silicon) was found to act as a superconductor at 17K – one of the first Type II superconductors to be discovered… Vanadium.

@chronicleflask
Vanadium is famous for its many colours and oxidation states. The ability to readily change oxidation state makes it a good catalyst, notably for the contact process, used to make sulfuric acid. Another element which is used in catalysis is rhodium.

@ndbrning
Rhodium is used in catalytic converters in cars to remove nitrogen oxides, carbon monoxide, and unburnt hydrocarbons. Other metals used as catalysts in these converters are platinum and palladium.

@DrMLHarris
In 1989 Pons & Fleischmann claimed to have observed cold fusion via electrolysis of heavy water on a palladium electrode. That was false, but controlled hot fusion in tokamaks is real. Tokamaks use superconducting wire made from an alloy of tin and… Niobium.

@sumants
Niobium is named after Niobe from Greek mythology, and unsurprisingly, the next element one period down is named for her father, Tantalus… Tantalum.

@Mark_Lorch
Tantalum is one of those elements that was discovered in the rocks of Ytterby. Which gives its name to 4 elements, including … erbium.

@sumants
Along with ytterbium and erbium, the same rocks near Ytterby also yielded… terbium.

@DrMLHarris
Today’s main source of Terbium, however, is a mineral called bastnasite, which is named after yet another Swedish mine, Bastnas. This mineral is also a major source of… Cerium.

@Stare_at_Air
Cerium is named after Ceres, a dwarf planet hypothesised to contain an ocean of liquid water. A similar ocean is thought to exist inside Europa, the Jovian moon, named after the figure in Greek mythology. Also named after it is Europe… Europium.

@sumants
Europium(III) oxide is used to activate yttrium phosphors, mostly to create red on television and computer screens. Yttrium is also one of the elements to come out of the Ytterby mine.

@sciencenotscary
Like Yttrium, Indium is also used in screens because of its importance as a component of the semiconductor indium tin oxide.

@ndbrning
Radioactive indium ions have been investigated by researchers for their potential use in radiopharmaceuticals for diagnosis and treatment of tumours. Radioactive actinium ions have been investigated for the same purpose.

@mrfarabaugh
Actinium assumes oxidation state +3 in nearly all its chemical compounds. The Ac(III) ion has an electron configuration that is isoelectronic with Radon.

@sciencenotscary
Radon, being inherently radioactive, is a nuisance background for sensitive particle detectors. Another nuisance is thorium.

@Stare_at_Air
Thorium is named after Thor, the Norse god of thunder, on whom characters in many a comic have been based over the years. Prometheus, a Titan from Greek mythology, has also made an appearance in several comics and gives his name to element 61… Promethium.

@Mark_Lorch
Henry Moseley showed that atomic numbers corresponded to a physical property of the elements. Using this he found that some atomic numbers had no known elements: the gaps were 43, 61 (promethium), 72, 75, 85 (astatine), and 87.

@Stare_at_Air
All the group 17 elements up to and including astatine (“unstable”) are named after their properties (Ts ruined it), but many elements in the rest of the table are too. We still have two of these left — one of them is “hard to get” (though stable)… Dysprosium.

@Mark_Lorch
(Dysprosium) And the other is Barium which is derived from mineral baryte in which it is found. This in turn comes from the Greek βαρύς (barys) meaning heavy.

@DrMLHarris
Even heavier than barium, and much harder to obtain due to its half-life of just 22 minutes, the next element has never been observed in bulk, though like the other alkalis it has been laser cooled and trapped. Step up… Francium.

@Mark_Lorch
Marguerite Catherine Perey (a student of Marie Curie) discovered Francium and named if after her home country. France gets another hat tip in the table in the form of Lutecium which is named from the latin for Paris.

@DrMLHarris
(Lutecium) Another Paris-based discoverer was Paul-Émile Lecoq de Boisbaudran. He discovered three elements. Two of them, gallium and dysprosium, have been done already, but the third was… Samarium.

@DrMLHarris
De Boisbaudran is credited as Samarium‘s discoverer, but a different French chemist, Eugène-Anatole Demarçay, actually isolated the pure metal. Demarçay destroyed his eyesight in a chemical explosion. The godfather of explosive chemistry is Alfred Nobel… Nobelium.

@Stare_at_Air
Nobel (Nobelium) may have set up the Nobel prize because he was worried about being remembered for his contribution to developing more effective weapons. Georgy Flyorov also played a role in weapons research, as he encouraged Stalin to start an atomic bomb project… Flerovium.

@DrMLHarris
(Flerovium) The most dangerous isotope in nuclear fallout, the hazards of which helped to persuade the US, UK and Soviet Union to ban above-ground weapons tests, is strontium-90, which is taken up in the bones… Strontium.

@sumants
One of the popular electrode materials in solid oxide fuel cells is LSM, which is a perovskite (ABO3) in which B positions have Mn, and A slots are occupied by strontium and… Lanthanum.

@DrMLHarris
The name “lanthanum” derives from the Ancient Greek for “to lie hidden.” X-rays are also good at revealing hidden things, from broken bones to chemical structures to black holes. They were discovered by Wilhelm Roentgen, who is honoured with Element 111… Roentgenium.

@sumants
Roentgenium was first created at the Helmholtz Centre for Heavy Ion Research in Darmstadt, from which we have… Darmstadtium.

@sumants
Several elements have been synthesized/discovered at the Helmholtz Center, including meitnerium, roentgenium, darmstadtium, bohrium, and… Hassium.

@sumants
(Hassium) I left out one more element synthesized at the Helmholtz Center: Copernicium.

@sumants
(Copernicium) The Helmholtz Center also helped confirm Element 116, which had been created partly in Dubna, and partly at the Lawrence Livermore NL, after which it was named: Livermorium.

@DrMLHarris
(Livermorium) All of these reactors used to discover ultra-heavy elements require good shielding against radioactivity. Because of its high neutron cross section, one of the elements used in shielding is… Gadolinium.

@Mark_Lorch
YEH!!! 👏 🥳 🎉 That was great fun! Thanks for playing! I honestly wondered if that was even doable!
#ElementTales

Periodic Table by Andy Brunning of Compound Interest (click for more)


Special thanks to Andrea Chlebikova (@Stare_at_Air) for keeping track of which elements had and hadn’t been covered as we went along.

You can also read an article about this project, published in Physics World, by Margaret Harris (@DrMLHarris).

Further thanks to: Mark Lorch, Andrea Chlebikova, Andy Brunning, Steve Maguire, Michael Farabaugh, Margaret Harris and Sumant Srivathsan. Follow the Twitter handle links to find these lovely people and give them a follow.

Let’s speed up the rate at which we recognise our female chemists

A little while back now I was researching my post on water when I came across a scientist which I hadn’t heard of before. And that was odd, because this person was one of the first to propose the idea of catalysis, which is a pretty important concept in chemistry, in fact, in science in general. Surely the name should be at least a bit familiar. Shouldn’t it?

And yet it wasn’t, and the more I read, the more surprised I was. Not only was this person clearly a brilliant thinker, they were also remarkably prescient.

Elizabeth Fulhame’s book was first published in 1794 (image by the Science History Institute, Public Domain)

So who was it? Her name was Elizabeth Fulhame, and we know very little about her, all things considered. Look her up and you won’t find any portraits, or even her exact dates of birth and death, despite the fact that her book, An Essay on
Combustion,
was published in more than one country and she, a Scottish woman, was made an honorary member of the Philadelphia Chemical Society in 1810 — remarkable achievements for the time.

As well as describing catalytic reactions for the first time, that book — first published in 1794 and surprisingly still available today — also contains a preface which includes the following:

But censure is perhaps inevitable; for some are so ignorant,
that they grow sullen and silent, and are chilled with horror
at the sight of any thing, that bears the semblance of learning,
in whatever shape it may appear; and should the spectre
appear in the shape of a woman, the pangs, which they suffer,
are truly dismal.

Obviously women are interested in physics. And also, apparently, in staring wistfully into open vacuum chambers whilst wearing unnecessary PPE (stock photos are great, aren’t they?)

Fulhame clearly did not suffer fools gladly (I think I would’ve liked her), and had also run across a number of people who felt that women were not capable of studying the sciences.

Tragically, 225 years later, this attitude still has not entirely gone away. Witness, for example, the recent article featuring an interview with Alessandro Strumia, in which he claimed that women simply don’t like physics. There were naturally a number of excellent rebuttals to this ludicrous claim, not least a brilliant annotated version of the article by Shannon Palus — which I recommend because, firstly, not behind a paywall and secondly, very funny.

Unfortunately, despite the acclaim she received at the time, Fulhame was later largely forgotten. One scientist who often gets the credit for “discovering” catalysis is Berzelius. There is no doubt that he was a remarkable chemist (you have him to thank for chemical notation, for starters), but he was a mere 15 years old when Fulhame published her book.

The RSC’s Breaking the Barriers report was published in 2018

In November last year, the Royal Society of Chemistry (RSC) launched its ‘Breaking the Barriers’ report, outlining issues surrounding women’s retention and progression in academia. As part of this project, they commissioned an interview with Professor Marina Resmini, Head of the Chemistry Department at Queen Mary University of London.

She pointed out that today there is an almost an equal gender split in students studying chemistry at undergraduate level in the United Kingdom, but admitted that there is still much to be done, saying:

“The two recent RSC reports ‘Diversity Landscape of the Chemical Sciences’ and ‘Breaking the Barriers’ have highlighted some of the key issues. Although nearly 50% of undergraduate students studying to become chemists are female, the numbers reaching positions of seniority are considerably less.”

Professor Resmini was keen to stress that there are many supportive men in academia, and that’s something we mustn’t forget. Indeed, this was true even in Fulhame’s time. Thomas P. Smith, a member of the Philadelphia Chemical Society’s organizing committee, applauded her work, saying “Mrs. Fulham has now laid such bold claims to chemistry that we can no longer deny the sex the privilege of participating in this science also.” Which may sound patronising to 21st century ears, but it was 1810 after all. Women wouldn’t even be trusted to vote for another century, let alone do tricky science.

I think I’ve found Strumia’s limousine; it’s bright red, very loud, and can only manage short distances.

Speaking of patronising comments, another thing that Strumia said in his interview was, “It is not as if they send limousines to pick up boys wanting to study physics and build walls to keep out the women.”

This is one of those statements that manages, at the same time, to be both true and also utterly absurd. Pupils, undergraduates, post-grads and post-docs do not exist in some sort of magical vacuum until, one day, they are presented with a Grand Choice to continue, or not, with their scientific career. Their decision to stop, if it comes, is influenced by a thousand, often tiny, things. Constant, subtle, nudges which oh-so-gently push them towards, or away, and which start in the earliest years of childhood. You only need to spend five minutes watching the adverts on children’s television to see that girls and boys are expected to have very different interests.

Textbooks may be studied by girls, but they rarely mention the work of female scientists.

So let’s end with another of Professor Resmini’s comments: that the work of past female scientists deserves greater recognition than it has received. This could not be more true, and this lack of representation is exactly one of those nudges I mentioned. Pick up a chemistry textbook and look for the pictures of female scientists: there might be a photo of Marie Curie, if you’re lucky. Kathleen Lonsdale usually gets a mention in the section on benzene in post-GCSE texts. But all too often, that’s about it. On the other hand, pictures of Haber, J. J. Thompson, Rutherford, Avogadro and Mendeleev are common enough that most chemistry students could pick them out of a lineup.

We should ask ourselves about the message this quietly suggests: that women simply haven’t done any “serious” chemistry (this is not the case, of course) and… perhaps never will?

Online, things have begun to shift. Dr Jess Wade has famously spent many, many hours adding the scientific contributions of women to Wikipedia, for example. It’s time things changed in print, too. Perhaps we could begin by starting the rates of reaction chapter in chemistry texts with a mention of Fulhame’s groundbreaking work.


EDIT: After I posted this, I learned that the Breaking Chemical Bias project is currently taking suggestions on the missing women scientists in the chemistry curriculum. I filled in the form for Fulhame, naturally! If this post has made you think of any other good examples, do head on over and submit their names.


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Carbon dioxide: the good, the bad, and the future

Carbon dioxide is a small molecule with the structure O=C=O

Carbon dioxide has been in and out of the news this summer for one reason or another, but why? Is this stuff helpful, or heinous?

It’s certainly a significant part of our history. Let’s take that history to its literal limits and start at the very beginning. To quote the great Terry Pratchett: “In the beginning, there was nothing, which exploded.”

(Probably.) This happened around 13.8 billion years ago. Afterwards, stuff flew around for a while (forgive me, cosmologists). Then, about 4.5 billion years ago, the Earth formed out of debris that had collected around our Sun. Temperatures on this early Earth were extremely hot, there was a lot of volcanic activity, and there might have been some liquid water. The atmosphere was mostly hydrogen and helium.

The early Earth was bashed about by other space stuff, and one big collision almost certainly resulted in the formation of the Moon. A lot of other debris vaporised on impact releasing gases, and substances trapped within the Earth started to escape from its crust. The result was Earth’s so-called second atmosphere.

An artist’s concept of the early Earth. Image credit: NASA. (Click image for more.)

This is where carbon dioxide enters stage left… er… stage under? Anyway, it was there, right at this early point, along with water vapor, nitrogen, and smaller amounts of other gases. (Note, no oxygen, that is, O2 – significant amounts of that didn’t turn up for another 1.7 billion years, or 2.8 billion years ago.) In fact, carbon dioxide wasn’t just there, it made up most of Earth’s atmosphere, probably not so different from Mars’s atmosphere today.

The point being that carbon dioxide is not a new phenomenon. It is, in fact, the very definition of an old phenomenon. It’s been around, well, pretty much forever. And so has the greenhouse effect. The early Earth was hot. Really hot. Possibly 200 oC or so, because these atmospheric gases trapped the Sun’s heat. Over time, lots and lots of time, the carbon dioxide levels reduced as it became trapped in carbonate rocks, dissolved in the oceans and was utilised by lifeforms for photosynthesis.

Fast-forward a few billion years to the beginning of the twentieth century and atmospheric carbon dioxide levels were about 300 ppm (0.03%), tiny compared to oxygen (about 20%) and nitrogen (about 78%).

Chemists and carbon dioxide

Flemish chemist Jan Baptist van Helmont carried out an experiment which eventually led to the discovery of carbon dioxide gas.

Let’s pause there for a moment and have a little look at some human endeavours. In about 1640 Flemish chemist Jan Baptist van Helmont discovered that if he burned charcoal in a closed vessel, the mass of the resulting ash was much less than that of the original charcoal. He had no way of knowing, then, that he had formed and collected carbon dioxide gas, but he speculated that some of the charcoal had been transmuted into spiritus sylvestris, or “wild spirit”.

In 1754 Scottish chemist Joseph Black noticed that heating calcium carbonate, aka limestone, produced a gas which was heavier than air and which could “not sustain fire or animal life”. He called it “fixed air”, and he’s often credited with carbon dioxide’s discovery, although arguably van Helmont got there first. Black was also the first person to come up with the “limewater test“, where carbon dioxide is bubbled through a solution of calcium hydroxide. He used the test to demonstrate that carbon dioxide was produced by respiration, an experiment still carried out in schools more than 250 years later to show that the air we breathe out contains more carbon dioxide than the air we breathe in.

In 1772 that most famous of English chemists, Joseph Priestley, experimented with dripping sulfuric acid (or vitriolic acid, as he knew it) on chalk to produce a gas which could be dissolved in water. Priestley is often credited with the invention of soda water as a result (more on this in a bit), although physician Dr William Brownrigg probably discovered carbonated water earlier – but he never published his work.

In the late 1700s carbon dioxide became more widely known as “carbonic acid gas”, as seen in this article dated 1853. In 1823 Humphry Davy and Michael Faraday manged to produce liquified carbon dioxide at high pressures. Adrien-Jean-Pierre Thilorier was the first to describe solid carbon dioxide, in 1835. The name carbon dioxide was first used around 1869, when the term “dioxide” came into use.

A diagram from “Impregnating Water with Fixed Air”, printed for J. Johnson, No. 72, in St. Pauls Church-Yard, 1772.

Back to Priestley for a moment. In the late 1800s, a glass of volcanic spring water was a common treatment for digestive problems and general ailments. But what if you didn’t happen to live near a volcanic spring? Joseph Black, you’ll remember, had established that CO2 was produced by living organisms, so it occurred to Priestly that perhaps he could hang a vessel of water over a fermentation vat at a brewery and collect the gas that way.

But it wasn’t very efficient. As Priestly himself said, “the surface of the fixed air is exposed to the common air, and is considerably mixed with it, [and] water will not imbibe so much of it by the process above described.”

It was then that he tried his experiment with vitriolic acid, which allowed for much greater control over the carbonation process. Priestly proposed that the resulting “water impregnated with fixed air” might have a number of medical applications. In particular, perhaps because the water had an acidic taste in a similar way that lemon-infused water does, he thought it might be an effective treatment for scurvy. Legend has it that he gave the method to Captain Cook for his second voyage to the Pacific for this reason. It wouldn’t have helped of course, but it does mean that Cook and his crew were some of the first people to produce carbonated water for the express purpose of drinking a fizzy drink.

Refreshing fizz

You will have noticed that, despite all his work, there is no fizzy drink brand named Priestly (at least, not that I know of).

Joseph Priestley is credited with developing the first method for making carbonated water.

But there is one called Schweppes. That’s because a German watchmaker named Johann Jacob Schweppe spotted Priestley’s paper and worked out a simpler, more efficient process, using sodium bicarbonate and tartaric acid. He went on to found the Schweppes Company in Geneva in 1783.

Today, carbonated drinks are made a little differently. You may have heard about carbon dioxide shortages this summer in the U.K. These arose because these days carbon dioxide is actually collected as a by-product of other processes. In fact, after several bits of quite simple chemistry that add up to a really elegant sequence.

From fertiliser to fizzy drinks

It all begins, or more accurately ends, with ammonia fertiliser. As any GCSE science student who’s been even half paying attention can tell you, ammonia is made by reacting hydrogen with nitrogen during the Haber process. Nitrogen is easy to get hold of – as I’ve already said it makes up nearly 80% of our atmosphere – but hydrogen has to be made from hydrocarbons. Usually natural gas, or methane.

This involves another well-known process, called steam reforming, in which steam is reacted with methane at high temperatures in the presence of a nickel catalyst. This produces carbon monoxide, a highly toxic gas. But no problem! React that carbon monoxide with more water in the presence of a slightly different catalyst and you get even more hydrogen. And some carbon dioxide.

Fear not, nothing is wasted here! The CO2 is captured and liquified for all sorts of food-related and industrial uses, not least of which is fizzy drinks. This works well for all concerned because steam reforming produces large amounts of pure carbon dioxide. If you’re going to add it to food and drinks after all, you wouldn’t want a product contaminated with other gases.

Carbon dioxide is a by-product of fertiliser manufacture.

We ended up with a problem this summer in the U.K. because ammonia production plants operate on a schedule which is linked to the planting season. Farmers don’t usually apply fertiliser in the summer – when they’re either harvesting or about to harvest crops – so many ammonia plants shut down for maintenance in April, May, and June. This naturally leads to reduction in the amount of available carbon dioxide, but it’s not normally a problem because the downtime is relatively short and enough is produced the rest of year to keep manufacturers supplied.

This year, though, natural-gas prices were higher, while the price of ammonia stayed roughly the same. This meant that ammonia plants were in no great hurry to reopen, and that meant many didn’t start supplying carbon dioxide in July, just when a huge heatwave hit the UK, coinciding with the World Cup football (which tends to generate a big demand for fizzy pop, for some reason).

Which brings us back to our atmosphere…

Carbon dioxide calamity?

Isn’t there, you may be thinking, too much carbon dioxide in our atmosphere? In fact, that heatwave you just mentioned, wasn’t that a global warming thing?  Can’t we just… extract carbon dioxide from our air and solve everyone’s problems? Well, yes and no. Remember earlier when I said that at the beginning of the twentieth century and atmospheric carbon dioxide levels were about 300 ppm (0.03%)?

Over the last hundred years atmospheric carbon dioxide levels have increased from 0.03% to 0.04%

Today, a little over 100 years later, levels are about 0.04%. This is a significant increase in a relatively short period of time, but it’s still only a tiny fraction of our atmosphere (an important tiny fraction nonetheless – we’ll get to that in a minute).

It is possible to distill gases from our air by cooling air down until it liquefies and then separating the different components by their boiling points. For example nitrogen, N2, boils at a chilly -196 oC whereas oxygen, O2, boils at a mere -183 oC.

But there’s a problem: CO2 doesn’t have a liquid state at standard pressures. It forms a solid, which sublimes directly into a gas. For this reason carbon dioxide is usually removed from cryogenic distillation mixtures, because it would freeze solid and plug up the equipment. There are other ways to extract carbon dioxide from air but although they have important applications (keep reading) they’re not practical ways to produce large volumes of the gas for the food and drink industries.

Back to the environment for a moment: why is that teeny 0.04% causing us such headaches? How can a mere 400 CO2 molecules bouncing around with a million other molecules cause such huge problems?

For that, I need to take a little diversion to talk about infrared radiation, or IR.

Infrared radiation was first discovered by the astronomer William Herschel in 1800. He was trying to observe sun spots when he noticed that his red filter seemed to get particularly hot. In what I’ve always thought was a rather amazing intuitive leap, he then passed sunlight through a prism to split it, held a thermometer just beyond the red light that he could see with his eyes, and discovered that the thermometer showed a higher temperature than when placed in the visible spectrum.

He concluded that there must be an invisible form of light beyond the visible spectrum, and indeed there is: infrared light. It turns out that slightly more than half of the total energy from the Sun arrives on Earth in the form of infrared radiation.

What has this got to do with carbon dioxide? It turns out that carbon dioxide, or rather the double bonds O=C=O, absorb a lot of infrared radiation. By contrast, oxygen and nitrogen, which make up well over 90% of Earth’s atmosphere, don’t absorb infrared.

CO2 molecules also re-emit IR but, having bounced around a bit, not necessarily in the same direction and – and this is the reason that tiny amounts of carbon dioxide cause not so tiny problems – they transfer energy to other molecules in the atmosphere in the process. Think of each CO2 molecule as a drunkard stumbling through a pub, knocking over people’s pints and causing a huge bar brawl. A single disruptive individual can, indirectly, cause a lot of others to find themselves bruised and bleeding and wondering what the hell just happened.

Like carbon dioxide, water vapour also absorbs infrared, but it has a relatively short lifetime in our atmosphere.

Water vapor becomes important here too, because while O2 and N2 don’t absorb infrared, water vapour does. Water vapour has a relatively short lifetime in our atmosphere (about ten days compared to a decade for carbon dioxide) so its overall warming effect is less. Except that once carbon dioxide is thrown into the mix it transfers extra heat to the water, keeping it vapour (rather than, say, precipitating as rain) for longer and pushing up the temperature of the system even more.

Basically, carbon dioxide molecules trap heat near the planet’s surface. This is why carbon dioxide is described as a greenhouse gas and increasing levels are causing global warming. There are people who are still arguing this isn’t the case, but truly, they’ve got the wrong end of the (hockey) stick.

It’s not even a new concept. Over 100 years ago, in 1912, a short piece was published in the Rodney and Otamatea Times which said: “The furnaces of the world are now burning about 2,000,000,000 tons of coal a year. When this is burned, uniting with oxygen, it adds about  7,000,000,000 tons of carbon dioxide to the atmosphere yearly. This tends to make the air a more effective blanket for the earth and to raise its temperature.”

This summer has seen record high temperatures and some scientists have been warning of a “Hothouse Earth” scenario.

This 1912 piece suggested we might start to see effects in “centuries”. In fact, we’re seeing the results now. As I mentioned earlier, this summer has seen record high temperatures and some scientists have been warning of “Hothouse Earth” scenario, where rising temperatures cause serious disruptions to ecosystems, society, and economies. The authors stressed it’s not inevitable, but preventing it will require a collective effort. They even published a companion document which included several possible solutions which, oddly enough, garnered rather fewer column inches than the “we’re all going to die” angle.

Don’t despair, DO something…

But I’m going to mention it, because it brings us back to CO2. There’s too much of it in our atmosphere. How can we deal with that? It’s simple really: first, stop adding more, i.e. stop burning fossil fuels. We have other technologies for producing energy. The reason we’re still stuck on fossil fuels at this stage is politics and money, and even the most obese of the fat cats are starting to realise that money isn’t much use if you don’t have a habitable planet. Well, most of them. (There’s probably no hope for some people, but we can at least hope that their damage-doing days are limited.)

There are some other, perhaps less obvious, sources of carbon dioxide and other greenhouse gases that might also be reduced, such as livestock, cement for building materials and general waste.

Forests trap carbon dioxide in land carbon sinks. More biodiverse systems generally store more carbon.

And then, we’re back to taking the CO2 out of the atmosphere. How? Halting deforestation would allow more CO2 to be trapped in so-called land carbon sinks. Likewise, good agricultural soil management helps to trap carbon underground. More biodiverse systems generally store more carbon, so if we could try to stop wiping out land and coastal systems, that would be groovy too. Finally, there’s the technological solution: carbon capture and storage, or CSS.

This, in essence, involves removing CO2 from the atmosphere and storing it in geological formations. The same thing the Earth has done for millenia, but more quickly. It can also be linked to bio-energy production in a process known as BECCS. It sounds like the perfect solution, but right now it’s energy intensive and expensive, and there are concerns that BECCS projects could end up competing with agriculture and damaging conservation efforts.

A new answer from an ancient substance?

Forming magnesite, or magnesium carbonate, may be one way to trap carbon dioxide.

Some brand new research might offer yet another solution. It’s another carbon-capture technology which involves magnesium carbonate, or magnesite (MgCO3). Magnesite forms slowly on the Earth’s surface, over hundreds of thousands of years, trapping carbon dioxide in its structure as it does.

It can easily be made quickly at high temperatures, but of course if you have to heat things up, you need energy, which might end up putting as much CO2 back in as you’re managing to take out. Recently a team of researchers at Trent University in Canada have found a way to form magnesite quickly at room temperature using polystyrene microspheres.

This isn’t something which would make much difference if, say, you covered the roof of everyone’s house with the microspheres, but it could be used in fuel-burning power generators (which could be burning renewables or even waste materials) to effectively scrub the carbon dioxide from their emissions. That technology on its own would make a huge difference.

And so here we are. Carbon dioxide is one of the oldest substances there is, as “natural” as they come. From breathing to fizzy drinks to our climate, it’s entwined in every aspect of our everyday existence. It is both friend and foe. Will we work out ways to save ourselves from too much of it in our atmosphere? Personally, I’m optimistic, so long as we support scientists and engineers rather than fight them…


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No need for slime panic: it’s not going to poison anyone

This is one of my favourite photos, so I’m using it again.

The school summer holidays are fast approaching and, for some reason, this always seems to get people talking about slime. Whether it’s because it’s a fun end-of-term activity, or it’s an easy bit of science for kids to do at home, or a bit of both, the summer months seem to love slimy stories. In fact, I wrote a piece about it myself in August 2017.

Which (hoho) brings me to the consumer group Which? because, on 17th July this year, they posted an article with the headline: “Children’s toy slime on sale with up to four times EU safety limit of potentially unsafe chemical” and the sub-heading: “Eight out of 11 popular children’s slimes we tested failed safety testing.”

The article is illustrated with lots of pots of colourful commercial slime pots with equally colourful names like Jupiter Juice. It says that, “exposure to excessive levels of boron could cause irritation, diarrhoea, vomiting and cramps in the short term,” and goes on to talk about possible risks of birth defects and developmental delays. Yikes. Apparently the retailer Amazon has removed several slime toys from sale since Which? got on the case.

The piece was, as you might expect, picked up by practically every news outlet there is, and within hours the internet was full of headlines warning of the dire consequences of handling multicoloured gloopy stuff.

Before I go any further, here’s a quick reminder: most slime is made by taking polyvinyl alcohol (PVA – the white glue stuff) and adding a borax solution, aka sodium tetraborate, which contains the element boron. The sodium tetraborate forms cross-links between the PVA polymer chains, and as a result you get viscous, slimy slime in place of runny, gluey stuff. Check out this lovely graphic created by @compoundchem for c&en’s Periodic Graphics:

The Chemistry of Slime from cen.acs.org (click image for link), created by Andy Brunning of @compoundchem

And so, back to the Which? article. Is the alarm justified? Should you ban your child from ever going near slime ever again?

Nah. Followers will remember that back in August last year, after I posted my own slime piece, I had a chat with boron-specialist David Schubert. He said at the time: “Borax has been repeated[ly] shown to be safe for skin contact. Absorption through intact skin is lower than the B consumed in a healthy diet” (B is the chemical symbol for the element boron). And then he directed me to a research paper backing up his comments.

Borax is a fine white powder, Mixed with water it can be used to make slime.

This, by the way, is all referring to the chemical borax – which you might use if you’re making slime. In pre-made slime the borax has chemically bonded with the PVA, and that very probably makes it even safer – because it’s then even more difficult for any boron to be absorbed through skin.

Of course, and this really falls under the category of “things no one should have to say,” don’t eat slime. Don’t let your kids eat slime. Although even if they did, the risks are really small. As David said when we asked this time: “Borates have low acute toxicity. Consumption of the amount of borax present in a handful of slime would make one sick to their stomach and possibly cause vomiting, but no other harm would result. The only way [they] could harm themselves is by eating that amount daily.”

It is true that borax comes with a “reproductive hazard” warning label. Which? pointed out in their article that there is EU guidance on safe boron levels, and the permitted level in children’s’ toys has been set at 300 mg/kg for liquids and sticky substances (Edited 18th July, see * in Notes section below).

EU safety limits are always very cautious – an additional factor of at least 100 is usually incorporated. In other words, for example, if 1 g/kg exposure of a substance is considered safe, the EU limit is likely to be set at 0.01 g/kg – so as to make sure that even someone who’s really going to town with a thing would be unlikely to suffer negative consequences as a result.

The boron limit is particularly cautious and is based on animal studies (and it has been challenged). The chemists I spoke to told me it’s not representative of the actual hazards. Boron chemist Beth Bosley pointed out that while it is true that boric acid exposure has been shown to cause fetal abnormalities when it’s fed to pregnant rats, this finding hasn’t been reproduced in humans. Workers handling large quantities of borate in China and Turkey have been studied and no reproductive effects have been seen.

Rat studies, she said, aren’t wholly comparable because rats are unable to vomit, which is significant because it means a rat can be fed a large quantity of a boron-containing substance and it’ll stay in their system. Whereas a human who accidentally ingested a similar dose would almost certainly throw up. Plus, again, this is all based on consuming substances such as borax, not slime where the boron is tied up in polymer chains. There really is no way anyone could conceivably eat enough slime to absorb these sorts of amounts.

These arguments aside, we all let our children handle things that might be harmful if they ate them. Swallowing a whole tube of toothpaste would probably give your child an upset stomach, and it could even be dangerous if they did it on a regular basis, but we haven’t banned toothpaste “just in case”. We keep it out of reach when they’re not supposed to be brushing their teeth, and we teach them not to do silly things like eating an entire tube of Oral-B. Same basic principle applies to slime, even if it does turn out to contain more boron than the EU guidelines permit.

In conclusion: pots of pre-made slime are safe, certainly from a borax/boron point of view, so long as you don’t eat them. The tiny amounts of boron that might be absorbed through skin are smaller than the amounts you’d get from eating nuts and pulses, and not at all hazardous.

Making slime at home can also be safe, if you follow some sensible guidelines like, say, these ones:

Stay safe with slime by following this guidance

Slime on, my chemistry-loving friends!


Notes:
* When I looked for boron safety limits the first time, the only number I could find was the rather higher 1200 mg/kg. So I asked Twitter if anyone could direct me to the value Which? were using. I was sent a couple of links, one of which contained a lot of technical documentation, but I think the most useful is probably a “guide to international toy safety” pamphlet which includes a “Soluble Element Migration Requirements” table. In the row for boron, under “Category II: Liquid or sticky materials”, the value is indeed given as 300 mg/kg.

BUT, there is also ” Category I: Dry, brittle, powder like or pliable materials” and the value there is the much higher 1,200 mg/kg. Which begs the question: does slime count as “pliable” or “sticky”? It suggests to me that, say, a modelling clay product (pliable) would have the 4x higher limit. But surely the risk of exposure would be essentially the same? If 1,200 mg/kg is okay for modelling clay, I can’t see why it shouldn’t be for slime. In the Which? testing, only the Jupiter Juice product exceeded the Category I limit, and then not by that much (1,400 mg/kg).

Also (the notes are going to end up being longer than the post if I’m not careful), these values are migration limits, not limits on the amount allowed in the substance in total. Can anyone show that more than 300 mg/kg is able to migrate from the slime to the person handling it? Very unlikey. But again, don’t eat slime.

This is not an invitation to try and prove me wrong.

I suppose it’s possible that someone could sell slime that’s contaminated with some other toxic thing. But that could happen with anything. The general advice to “wash your/their hands and don’t eat it” will take you a long way.


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A Dash of Science, Social Media and VARD

Yesterday I recorded a podcast with Matthew Lee Loftus (from The Credible Hulk) and Christopher El Sergio for A Dash of Science, all about science communication and social media. It was a brilliant chat – I won’t go into lots of details of what we covered, but if you’d like to hear it (you know you do!) the direct link is: Communicating Science on Social Media. You can also pick it up on iTunes and/or Tune In.

After our conversation ended I remembered something I developed little while ago, after marking a particularly infuriating research homework where a quarter of the class wrote down that Mendeleev was awarded a Nobel prize for his work on the Periodic Table. For the record: he never received the honour. He was recommended for the prize but famously (at least, I thought it was famously!) the 1906 prize was given to Henri Moissan instead, probably due to a grudge held by Svante Arrhenius of Arrhenius Equation fame (it’s a good story, check it out).

Mendeleev was never awarded a Nobel prize.

Does it really matter if a few students believe that Mendeleev won a Nobel prize? That’s not really harming anyone, is it? Maybe not, but on the other hand, perhaps it’s part of a long and slippery slope greased with ‘alternative facts’ which is leading us to, well, shall we say, situations and decisions that may not be in our best interests as a society.

How to encourage students to do at least a little bit of fact-checking? Of course, you could produce a long list of Things That One Should Do to check information, but I reasoned that while students might read such a list, and even agree with the principles, they were unlikely to get into the habit of applying them and probably quite likely to immediately forget all about it.

Instead I tried to come up with something short, simple and memorable, and here it is (feel free to share this):

Fact-checking isn’t easy; it’s VARD

The four points I focused on spell out VARD, which stands for…

Verify

V is for verify, which means: can you find other sources saying the same thing? Now, chances are, you can always find something that agrees with a particular piece of information, if you look hard enough. There are plenty of sites out there that will tell you that lemons ‘alkalise’ the body, for example (they don’t), that it’s safe to eat apricot kernels (it’s not) and that black salve is an effective treatment for skin cancer (nope).

However, if you’re reasonably open-minded when you start, chances are good that you’ll find both sides of the ‘story’ and that will, at the very least, get you thinking about which version is more trustworthy.

Author

A is for author. I often hear swathes of content being disparaged purely based on its nature. You know the sort of thing: “that’s just a blog,” or “you can’t trust newspaper articles”. I think this is wrong-headed. What matters more is who wrote that piece and what are their qualifications? I’d argue that a blog post about medical issues written by a medical doctor (for example, virtually anything on the marvellous Science Based Medicine) is likely to be a pretty reliable source. Conversely, there’s been more than one thing that’s made it into the scientific literature which has later turned out to be flawed or even flat false (such as Wakefield’s famous 1998 paper). It’s also worth asking what someone’s background is: Stephanie Seneff, for example, is highly qualified in the fields of artificial intelligence and computer science, but does that mean we should trust her controversial opinions in biology and medicine? Probably not.

You may not always be able to tell who the author is, or have time to dig into their motivations, but it’s nevertheless a good question to keep in the back of your mind.

Reasonableness

Be honest: is that story really likely? Or is it just shocking?

R is for reasonableness. Which is a pain to spell or even say, but it’s important so I’m sticking with it. It’s a sense-check. Human beings love a good story, and the best stories have unexpected twists and turns. That’s why medical scare-stories pop up in newspapers with such depressing regularity. No, ketchup isn’t giving you cancer. No, our children really aren’t being poisoned by plastics. But the truth doesn’t always make a good headline. In fact, when it comes to science, the more some ‘exciting finding’ is plastered over news sites, the less you should probably trust it – because the chances are that the exciting version being reported bears almost no resemblance to the researchers’ original conculsions.

Be honest and ask yourself: does this really seem likely? Or would I just like it to be true because it’s a great story?

Date

If a surprising story has just appeared, give it twenty-four hours – chances are if there are major issues with the information someone else will come forward.

D is for date. The obvious situation is when information is so old that it’s been superseded by something else. This is easy: just look for something more recent. However, the other side of this coin is probably more relevant in these days of rolling news and instant sharing of articles: something can blow up at short notice, especially something topical, and it later turns out that not all the facts were known. Take, for example, the famous green swimming pools in the 2016 Olympics, which more than one writer attributed to copper salts in the pool water before the full facts were revealed a few days later. Inevitably, the ‘corrected’ version is far less interesting than the earlier speculation, and so that’s what everyone remembers.

If something controversial and shocking has just appeared, give it twenty-four hours. If there’s something terribly wrong with it, chances are someone will pick up on it in that time.

It’s not easy; it’s VARD

And that’s it: Verify, Author, Reasonableness, Date. It doesn’t cover every eventuality, but if you keep these points in the back of your mind it will definitely help you to separate the ‘probably true’ from the ‘almost certainly bollocks’.

Good luck out there!

Now why not go and listen to that podcast 🙂


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Chemical du jour: how bad is BPA, really?

BPA is an additive in many plastics

When I was writing my summary of 2017 I said that there would, very probably, be some sort of food health scare at the start of 2018. It’s the natural order of things: first we eat and drink the calorie requirement of a small blue whale over Christmas and New Year, and then, lo, we must be made to suffer the guilt in January. By Easter, of course, it’s all forgotten and we can cheerfully stuff ourselves with chocolate eggs.

Last year it was crispy potatoes, and the year before that it was something ridiculous about sugar in ketchup causing cancer (it’s the same sugar that’s in everything, why ketchup? Why?). This year, though, it seems that the nasty chemical of the day is not something that’s in our food so much as around it.

Because this year the villain of the piece appears to be BPA, otherwise known as Bisphenol A or, to give it its IUPAC name, 4,4′-(propane-2,2-diyl)diphenol.

BPA is an additive in plastics. At the end of last year an excellent documentary aired on the BBC called Blue Planet II, all about our planet’s oceans. It featured amazing, jaw-dropping footage of wildlife. It also featured some extremely shocking images of plastic waste, and the harm it causes.

Plastic waste is a serious problem

Plastic waste, particularly plastic waste which is improperly disposed of and consequently ends up in the wrong place, is indisputably something that needs to be addressed. But this highlighting of the plastic waste problem had an unintended consequence: where was the story going to go? Everyone is writing about how plastic is bad, went (I imagine) editorial meetings in offices around the country – find me a story showing that plastic is even WORSE than we thought!

Really, it was inevitable that a ‘not only is plastic bad for the environment, but it’s bad for you, too!’ theme was going to emerge. It started, sort of, with a headline in The Sun newspaper: “Shopping receipts could ‘increase your cancer risk’ – as 93% contain dangerous chemicals also linked to infertility. Shopping receipts are, of course, not made of plastic – but the article’s sub-heading stated that “BPA is used to make plastics”, so the implication was clear enough.

Then the rather confusing: “Plastic chemical linked to male infertility in majority of teenagers, study suggests” appeared in The Telegraph (more on this in a bit), and the whole thing exploded. Search for BPA in Google News now and there is everything from “5 Ways to Reduce Your Exposure to Toxic BPA” to “gender-bending chemicals found in plastic and linked to breast and prostate cancer are found in 86% of teenagers”.

Yikes. It’s all quite scary. It’s true that right now you can’t really avoid plastic. Look around you and it’s likely that you’ll immediately see lots of plastic objects, and that’s before you even try to consider all the everyday things which have plastic coatings that aren’t immediately obvious. If you have young children, you’re probably drowning in plastic toys, cups, plates and bottles. We’re pretty much touching plastic continually throughout our day. How concerned should we be?

As the Hitchiker’s Guide to the Galaxy says, Don’t Panic. Plastic (like planet Earth in the Guide) can probably be summed up as mostly harmless, at least from a BPA point of view if not an environmental one.

BPA is a rather pleasingly symmetrical molecule with two phenol groups. (A big model of this would make a wonderfully ironic pair of sunglasses, wouldn’t it?) It was first synthesized by the Russian chemist Alexander Dianin in the late 19th century. It’s made by reacting acetone – which is where the “A” in the name comes from – with two phenol molecules. It’s actually a very simple reaction, although the product does need to be carefully purified, since large amounts of phenol are used to ensure a good yield.

It’s been used commercially since the fifties, and millions of tonnes of BPA are now produced worldwide each year. BPA is used to make plastics which are clear and tough – two characteristics which are often valued, especially for things like waterproof coatings, bottles and food containers.

The concern is that BPA is an endocrine disruptor, meaning that it interferes with hormone systems. In particular, it’s a known xenoestrogen, in other words it mimics the female hormone estrogen. Animal studies have suggested possible links to certain cancers, infertility, neurological problems and other diseases. A lot of the work is fairly small-scale and, as I’ve mentioned, focused on animal studies (rather than looking directly at effects in humans). Where humans have been studied it’s usually been populations that are exposed to especially high BPA levels (epoxy resin painters, for example). Still, it builds up into quite a damning picture.

BPA has been banned from baby bottles in many countries, including the USA and Europe

Of course, we don’t normally eat plastic, but BPA can leach from the plastic into the food or drink that’s in the plastic, and much more so if the plastic is heated. Because of these concerns, BPA has been banned from baby bottles (which tend to be heated, both for sterilisation and to warm the milk) in several countries, including the whole of Europe, for some years now. “BPA free” labels are a fairly common sight on baby products these days. BPA might also get onto our skin from, for example, those thermal paper receipts The Sun article mentioned, and then into our mouths when we eat. Our bodies break down and excrete the chemical fairly quickly, in as little as 6 hours, but because it’s so common in our environment most of us are continually meeting new sources of it.

How much are we getting, though? This is a critical question, because as I’m forever saying, the dose makes the poison. Arsenic is a deadly poison at high levels, but most of us – were we to undergo some sort of very sensitive test – would probably find we have traces of it in our systems, because it’s a naturally-occuring mineral. It’s nothing to worry about, unless for some reason the levels become too high.

When it comes to BPA, different countries have different guidelines. The European Food Safety Authority recommended in January 2015 that the TDI (tolerable daily intake) should be reduced from 50 to 4 µg/kg body weight/day (there are plans for a new assessment in 2018, so it might change again). For a 75 kg adult, that translates to about 0.0003 g per day. A USA Federal Drug and Administration document from 2014 suggests a NOAEL (no-observed-adverse-effect-level) of 5 mg/kg bw/day, which translates to 0.375 g per day for the same 75 kg adult. NOAEL values are usually much higher than TDIs, so these two figures aren’t as incompatible as they might appear. Tolerable daily intake values tend to have a lot of additional “just in case” tossed into them – being rather more guidance than science.

The European Food Standards Authority published a detailed review of the evidence in 2015 (click for a summary)

So, how much BPA are we exposed to? I’m going to stick to Europe, because that’s where I’m based (for now…), and trying to look at all the different countries is horribly complicated. Besides, EFSA produced a really helpful executive summary of their findings in 2015, which makes it much easier to find the pertinent information.

The key points are these: most of our exposure comes from food. Infants, children and adolescents have the highest dietary exposures to BPA, probably because they eat and drink more per kilogram of body weight. The estimated average was 0.375 µg/kg bw per day.  For adult women the estimated average was 0.132 µg/kg bw per day, and for men it was 0.126 µg/kg bw per day.

When it came to thermal paper and other non-dietary exposure (mostly from dust, toys and cosmetics), the numbers were smaller, but the panel admitted there was a fair bit of uncertainty here. The total exposure from all sources was somewhere in the region of 1 µg/kg bw per day for all the age groups, with adolescents and young children edging more toward values of 1.5 µg/kg bw per day (this will be important in a minute).

Note that all of these numbers are significantly less than the, conservative, tolerable daily intake value of 4 µg/kg bw per day recommended by EFSA.

Here’s the important bit: the panel concluded that there is “no health concern for BPA at the estimated levels of exposure” as far as diet goes. They also said that this applied “to prenatally exposed children” (in other words, one less thing for pregnant women to worry about).

When it came to total exposure, i.e. diet and exposure from other sources such as thermal paper they concluded that “the health concern for BPA is low at the estimated levels of exposure”.

The factsheet that was published alongside the full document summarises the results as follows: “BPA poses no health risk to consumers because current exposure to the chemical is too low to cause harm.”

Like I said: Don’t Panic.

What about those frankly quite terrifying headlines? Well, firstly The Sun article was based on some work conducted on a grand total of 208 receipts collected in Southeast Michigan in the USA from only 39 unique business locations. That’s a pretty small sample and not, I’d suggest, perhaps terribly relevant to the readership of a British newspaper. Worse, the actual levels of BPA weren’t measured in the large majority of samples – they only tested to see if it was there, not how much was there. There was nothing conclusive at all to suggest that the levels in the receipts might be enough to “increase your cancer risk”. All in all, it was pretty meaningless. We already knew there was BPA in thermal receipt paper – no one was hiding that information (it’s literally in the second paragraph of the Wikipedia page on BPA).

The Telegraph article, and the many others it appeared to spawn, also weren’t based on especially rigorous work and, worse, totally misrepresented the findings in any case. Firstly, let’s consider that headline: “Plastic chemical linked to male infertility in majority of teenagers, study suggests”. What does that mean? Are they suggesting that teenagers are displaying infertility? No, of course not. They didn’t want to put “BPA” in the headline because that, apparently, would be too confusing for their readers. So instead they’ve replaced “BPA” with “plastic chemical linked to male infertility”, which is so much more straightforward, isn’t it?

And they don’t mean it’s linked to infertility in the majority of teenagers, they mean it’s linked to infertility and it’s in the majority of teenager’s bodies. I do appreciate that journalists rarely write headlines – this isn’t a criticism of the poor writer who turned in perfectly good copy – but that is confusing and misleading headline-writing of the highest order. Ugh.

Plus, as I commented back there, that wasn’t even the conclusion of the study, which was actually an experiment carried out by students under the supervision of a local university. The key finding was not that, horror, teenagers have BPA in their bodies. The researchers assumed that almost all of the teenagers would have BPA in their bodies – as the EFSA report showed, most people do. No, the conclusion was actually that the teenagers – 94 of them – had been unable to significantly reduce their levels of BPA by changing their diet and lifestyle. Although the paper admits the conditions weren’t well-controlled. Basically, they asked a group of 17-19 year-olds to avoid plastic, and worked on the basis that their account of doing so was accurate.

And how much did the teenagers have in their samples? The average was 1.22 ng/ml, in urine samples (ng = nanogram). Now, even if we assume that these levels apply to all human tissue (which they almost certainly don’t) and that therefore the students had roughly 1.22 ng per gram of body weight, that only translates to, very approximately, 1.22 micrograms (µg) per kilogram of body weight.

Wait a second… what did EFSA say again…. ah yes, they estimated total exposures of 1.449 µg/kg bw per day for adolescents.

Sooooo basically a very similar value, then? And the EFSA, after looking at multiple studies in painstaking detail, concluded that “BPA poses no health risk to consumers”.

Is this grounds for multiple hysterical, fear-mongering headlines? I really don’t think it is.

It is interesting that the teenagers were unable to reduce their BPA levels. Because it’s broken down and excreted quite quickly by the body, you might expect that reducing exposure would have a bigger effect – but really all we can say here is that this needs to be repeated with far more tightly-controlled conditions. Who knows what the students did, and didn’t, actually handle and eat. Perhaps their school environment contains high levels of BPA in dust for some reason (new buildings or equipment, maybe?), and so it was virtually impossible to avoid. Who knows.

In summary, despite the scary headlines there really is no need to worry too much about BPA from plastics or receipts. It may be worth avoiding heating plastic, since we know that increases the amound of BPA that makes its way into food – although it’s important to stress that there’s no evidence that microwaving plastic containers causes levels to be above safe limits. Still, if you wanted to be cautious you could choose to put food into a ceramic or glass bowl, covered with a plate rather than clingfilm. It’ll save you money on your clingfilm bills anyway, and it means less plastic waste, which is no bad thing.

Roll on Easter…


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Hydrogen peroxide: another deadly alternative?

I’m sure most people have heard of hydrogen peroxide. It’s used as a disinfectant and, even if you’ve never used it for that, you probably at least know that it’s used to bleach hair. It’s where the phrase “peroxide blonde” comes from, after all. Hydrogen peroxide, and its formula, is so famous that there’s an old chemistry joke about it:

(I have no idea who to credit for the original drawing – if it’s you, leave me a message.)

To save you squinting at the text, it goes like this:
Two men walk into a bar. The first man says, “I’ll have some H2O.”
The second man says, “I’ll have some H2O, too.”
The barman brings the drinks. The second man dies horribly.

Now I think about it, it’s not a terribly funny joke.

Hydrogen peroxide has an extra oxygen atom in the middle.

Never mind. You get the idea. H2O2 (“H2O, too”) is the formula for hydrogen peroxide. Very similar to water’s formula, except with an extra oxygen atom in the middle. In fact, naturopaths – purveyors of alternative therapies – often refer to hydrogen peroxide as “water with extra oxygen”. But this is really misleading because, to torture a metaphor, that extra oxygen makes hydrogen peroxide the piranha to water’s goldfish.

Water, as we know, is pretty innocuous. You should try not to inhale it obviously, or drink more than about six litres in one go, but otherwise, its pretty harmless. Hydrogen peroxide, on the other hand, not so much. The molecule breaks apart easily, releasing oxygen. That makes it a strong oxidising agent. It works as a disinfectant because it basically blasts cells to pieces. It bleaches hair because it breaks down pigments in the hair shaft. And, as medical students will tell you, it’s also really good at cleaning up blood stains – because it oxidises the iron in haemoglobin to Fe3+, which is a pale yellow colour*.

Dilute hydrogen peroxide is readily available.

In its dilute form, hydrogen peroxide is a mild antiseptic. Three percent and even slightly more concentrated solutions are still readily available in high-street pharmacies. However, even these very dilute solutions can cause skin and eye irritation, and prolonged skin contact is not recommended. The trouble is, while it does destroy microbes, it also destroys healthy cells. There’s been a move away from using hydrogen peroxide for this reason, although it is still a popular “home” remedy.

More concentrated** solutions are potentially very dangerous, causing severe skin burns. Hydrogen peroxide is also well-known for its tendency to react violently with other chemicals, meaning that it must be stored, and handled, very carefully.

All of which makes the idea of injecting into someone’s veins particularly horrific.

But this is exactly what some naturopaths are recommending, and even doing. The idea seems to have arisen because hydrogen peroxide is known to damage cancer cells. But so will a lot of other dangerous substances – it doesn’t mean it’s a good idea to inject them. Hydrogen peroxide is produced by certain immune cells in the body, but only in a very controlled and contained way. This is definitely a case where more isn’t necessarily better.

The use of intravenous hydrogen peroxide appears to have begun in America, but it may be spreading to the UK. The website yestolife.org.uk, which claims to empower people with cancer to “make informed decisions”, states “The most common form of hydrogen peroxide therapy used by doctors calls for small amounts of 30% reagent grade hydrogen peroxide added to purified water and administered as an intravenous drip.”

30% hydrogen peroxide is really hazardous stuff. It’s terrifying that this is being recommended to vulnerable patients.

Other sites recommend inhaling or swallowing hydrogen peroxide solutions, both of which are also potentially extremely dangerous.

If anyone ever suggests a hydrogen peroxide IV, run very fast in the other direction.

In 2004 a woman called Katherine Bibeau died after receiving intravenous hydrogen peroxide treatment from James Shortt, a man from South Carolina who called himself a “longevity physician”. According to the autopsy report she died from systemic shock and DIC – the formation of blood clots in blood vessels throughout the body. When her body arrived at the morgue, she was covered in purple-black bruises.

Do I need to state the obvious? If anyone suggests injecting this stuff, run. Run very fast, in the other direction. Likewise if they suggest drinking it. It’s a really stupid idea, one that could quite literally kill you.


* As anyone who’s ever studied chemistry anywhere in my vicinity will tell you, “iron three is yellow, like wee.”


** The concentration of hydrogen peroxide is usually described in one of two ways: percentage and “vol”. Percentage works as you might expect, but vol is a little different. It came about for practical, historical reasons. As Prof. Poliakoff comments in this video, hydrogen peroxide is prone to going “flat” – leave it in the bottle for long enough and it gradually decomposes until what you actually have is a bottle of ordinary water. Particularly in the days before refrigeration (keeping it cold slows down the decomposition) a bottle might be labelled 20%, but actually contain considerably less hydrogen peroxide.

What to do? The answer was quite simple: take, say, 1 ml of hydrogen peroxide, add something which causes it to decompose really, really fast (lots of things will do this: potassium permanganate, potassium iodide, yeast, even liver) and measure the volume of oxygen given off. If your 1 ml of hydrogen peroxide produces 10 ml of oxygen, it’s 10 vol. If it produces 20, it’s 20 vol. And so on. Simple. 3% hydrogen peroxide, for the record, is about 10 vol***. Do not mix up these numbers.


*** Naturally, there are mole calculations to go with this. Of course there are. For A-level Chemists, here’s the maths (everyone else can tune out; I’m adding this little footnote because I found this information strangely hard to find):

Hydrogen peroxide decomposes as shown in this equation:
2H2O2 –> 2H2O + O2

Let’s imagine we decompose 1 ml of hydrogen peroxide and obtain 10 mls of oxygen.

Assuming the oxygen gas occupies 24 dm3 (litres), or 24000 mls, at standard temperature and pressure, 10 mls of oxygen is 10 / 24000 = 0.0004167 moles. But, according to the equation, we need two molecules of hydrogen peroxide to make one molecule of oxygen, so we need to multiply this number by two, giving us 0.0008333 moles.

To get the concentration of the hydrogen peroxide in the more familar (to chemists, anyway) mol dm-3, just divide that number of moles by the volume of hydrogen peroxide. In other words:

0.0008333 mols / 0.001 dm3 = 0.833 mol dm-3

If you really want to convert this into a percentage by mass (you can see why people stick with “vol” now, right?), then:

0.833 mol (in the litre of water) x 34 g mol-1 (the molecular mass of H2O2)
= 28.32 g (in 1000 g of water)

Finally, (28.32 / 1000) x 100 = 2.8% or, rounding up, 3%

In summary (phew):
10 vol hydrogen peroxide = 0.83 mol dm-3 = 3%


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