How many scientists does it take to discover five elements? More than you might think…

My last post chronicled (see what I did there?) a meandering stroll through all 118 elements in the periodic table. As I read through all the pieces of that thread, I kept wanting to find out more about some of the stories. This is the international year of the periodic table, after all — what better time to go exploring?

But, here’s the thing: 118 is a lot. It took ages even just to collect all the (mostly less than) 280-character tweets together. Elemental stories span the whole of human existence and are endlessly fascinating, but telling all of them in any kind of detail would take whole book (not a small one, either) and would be a project years in the making. So, how about instead having a look at some notable landmarks? A sort of time-lapse version of elemental history and discovery, if you will…


The word “carbon” comes from the Latin “carbo”, meaning coal and charcoal.

Let’s begin the story with carbon: fourth most abundant element in the universe and tenth most abundant in the Earth’s crust (give or take). When the Earth first formed, about 4.54 billion years ago, volcanic activity resulted in an atmosphere that was mostly carbon dioxide. The very earliest forms of life evolved to use carbon dioxide through photosynthesis. Carbon-based compounds make up the bulk of all life on this planet today, and carbon is the second most abundant element in the human body (after oxygen).

When we talk about discovering elements, our minds often leap to “who”. But, as we’ll see throughout this journey, that’s never an entirely straightforward question. The word “carbon” comes from the Latin carbo, meaning coal and charcoal. Humans have known about charcoal for many thousands of years — after all, if you can make a fire, it’s not long before you start to wonder if you can do something with this leftover black stuff. We’ll never know who first “discovered” carbon. But we can be sure of one thing: it definitely wasn’t an 18th century European scientist.

Diamond is a form of carbon used by humans for over 6000 years.

Then there are diamonds, although of course it took people a bit longer to understand how diamonds and other forms of carbon were connected. Human use of diamonds may go back further than we imagine, too. There’s evidence that the Chinese used diamonds to grind and polish ceremonia tools as long as 6,000 years ago.

Even the question of who first identified carbon as an element isn’t entirely straightforward. In 1722, René Antoine Ferchault de Réaumur demonstrated that iron was turned into steel by absorbing some substance. In 1772, Lavoisier showed for the first time that diamonds could burn (contrary to a key plot point in a 1998 episode of Columbo).

In 1779, Scheele demonstrated that graphite wasn’t lead, but rather was a form of charcoal that formed aerial acid (today known as carbonic acid) when it was burned and the products dissolved in water. In 1786 Claude Louis Berthollet, Gaspard Monge and C. A. Vandermonde again confirmed that graphite was mostly carbon, and in 1796, Smithson Tennant showed that burning diamond turned limewater milky — the established test for carbon dioxide gas — and argued that diamond and charcoal were  chemically identical.

Even that isn’t quite the end of the story: fullerenes were discovered 1985, and Harry Kroto, Robert Curl, and Richard Smalley were awarded a Nobel Prize for: “The discovery of carbon atoms bound in the form of a ball” in 1996.

Type “who discovered carbon” into a search engine and Lavoisier generally appears, but really? He was just one of many, most of whose names we’ll never know.


Brass, an alloy of zinc, has been used for thousands of years.

Now for the other end of the alphabet: zinc. It’s another old one, although not quite as old as carbon. Zinc’s history is inextricably linked with copper, because zinc ores have been used to make brass alloys for thousands of years. Bowls made of alloyed tin, copper and zinc have been discovered which date back to at least 9th Century BCE, and many ornaments have been discovered which are around 2,500 years old.

It’s also been used in medicine for a very long time. Zinc carbonate pills, thought to have been used to treat eye conditions, have been found on a cargo ship wrecked off the Italian coast around 140 BCE, and zinc is mentioned in Indian and Greek medical texts as early as the 1st century CE. Alchemists burned zinc in air in 13th century India and collected the white, woolly tufts that formed. They called it philosopher’s wool, or nix alba (“white snow”). Today, we know the same thing as zinc oxide.

The name zinc, or something like it, was first documented by Paracelsus in the 16th century — who called it “zincum” or “zinken” in his book, Liber Mineralium II. The name might be derived from the German zinke, meaning “tooth-like” — because crystals of tin have a jagged, tooth-like appearance. But it could also suggest “tin-like”, since the German word zinn means tin. It might even be from the Persian word سنگ, “seng”, meaning stone.

These days, zinc is often used as a coating on other metals, to prevent corrosion.

P. M. de Respour formally reported that he had extracted metallic zinc from zinc oxide in 1668, although as I mentioned above, in truth it had been extracted centuries before then. In 1738, William Champion patented a process to extract zinc from calamine (a mixture of zinc oxide and iron oxide) in a vertical retort smelter, and Anton von Swab also distilled zinc from calamine in 1742.

Despite all that, credit for discovery of zinc usually goes to Andreas Marggraf, who’s generally considered the first to recognise zinc as a metal in its own right, in 1746.


Evidence of helium was first discovered during a solar eclipse.

Ironically for an element which is (controversially) used to fill balloons, helium’s discovery is easier to pin down. In fact, we can name a specific day: August 18, 1868. The astronomer Jules Janssen was studying the chromosphere of the sun during a total solar eclipse in Guntur, India, and found a bright, yellow line with a wavelength of 587.49 nm.

In case you thought this was going to be simple, though, he didn’t recognise the significance of the line immediately, thinking it was caused by sodium. But then, later the same year, Norman Lockyer also observed a yellow line in the solar spectrum — which he concluded was caused by an element in the Sun unknown on Earth. Lockyer and Edward Frankland named the element from the Greek word for the Sun, ἥλιος (helios).

Janssen and Lockyer may have identified helium, but they didn’t find it on Earth. That discovery was first made by Luigi Palmieri, analysing volcanic material from Mount Vesuvius in 1881. And it wasn’t until 1895 that William Ramsay first isolated helium by treating the mineral cleveite (formula UO2) with acid whilst looking for argon.

Mendeleev’s early versions of the periodic table, such as this one from 1871, did not include any of the noble gases (click for image source).

Interestingly, Mendeleev’s 1869 periodic table had no noble gases as there was very little evidence for them at the time. When Ramsay discovered argon, Mendeleev assumed it wasn’t an element because of its unreactivity, and it was several years before he was convinced that any of what we now call the noble gases should be included. As a result, helium didn’t appear in the periodic table until 1902.

Who shall we say discovered helium? The astronomers, who first identified it in our sun? Or the chemists, who managed to collect actual samples on Earth? Is an element truly “discovered” if you can’t prove you had actual atoms of it — even for a brief moment?


So far you may have noticed that all of these discoveries have been male dominated. This is almost certainly not because women were never involved in science, as there are plenty of records suggesting that women often worked in laboratories in various capacities — it’s just that their male counterparts usually reported the work. As a result the men got the fame, while the women’s stories were, a lot of the time, lost.

Marguerite Perey discovered francium (click for image source).

Of course, the name that jumps to mind at this point is Marie Curie, who famously discovered polonium and radium and had a third element, curium, named in honour of her and her husband’s work. But she’s famous enough. Let’s instead head over to the far left of the periodic table and have a look at francium.

Mendeleev predicted there ought to be an element here, following the trend of the alkali metals. He gave it the placeholder name of eka-caesium, but its existence wasn’t to be confirmed for some seventy years. A number of scientists claimed to have found it, but its discovery is formally recorded as having been made in January 1939 by Marguerite Perey. After all the previous failures, Perey was incredibly meticulous and thorough, carefully eliminating all possibility that the unknown element might be thorium, radium, lead, bismuth, or thallium.

Perey temporarily named the new alkali metal actinium-K (since it’s the result of alpha decay of 227Ac), and proposed the official name of catium (with the symbol Cm), since she believed it to be the most electropositive cation of the elements.

But the symbol Cm was assigned to curium, and Irène Joliot-Curie, one of Perey’s supervisors, argued against the name “catium”, feeling it suggested the element was something to do with cats. Perey then suggested francium, after her home country of France, and this was officially adopted in 1949.

A sample of uraninite containing perhaps 100,000 atoms of francium-223 (click for image source).

Francium was the last element to be discovered in nature. Trace amounts occur in uranium minerals, but it’s incredibly scarce. Its most stable isotope has a half life of just 22 minutes, and bulk francium has never been observed. Famously, there’s at most 30 g of francium in the Earth’s crust at any one time.

Of all the elements I’ve mentioned, this is perhaps the most clear-cut case. Perey deservedly takes the credit for discovering francium. But even then, she wouldn’t have been able to prove so conclusively that the element she found wasn’t something else had it not been for all the false starts that came before. And then there are all the other isotopes of francium, isolated by a myriad of scientists in the subsequent years…


All of which brings us to one of the last elements to be discovered: tennessine (which I jokingly suggested ought to be named octarine back in 2016). As I mentioned above, francium was the last element to be discovered in nature: tessessine doesn’t exist on Earth. It has only ever been created in a laboratory, by firing a calcium beam into a target made of berkelium (Bk) and smashing the two elements together in a process called nuclear fusion.

Element 117, tennessine, was named after Tennessee in the USA.

Like tennessine, berkelium isn’t available on Earth and had to be made in a nuclear reactor at Oak Ridge National Laboratory (ORNL) in Tennessee — the reason for the new element’s name. One of the scientists involved, Clarice E. Phelps, is believed to be the first African American to discover a chemical element in recent history, having worked on the purification of the 249Bk before it was shipped to Russia and used to help discover element 117.

Tennessine’s discovery was officially announced in Dubna in 2010 — the result of a Russian-American collaboration — and the name tennessine was officially adopted in November 2016.

Who discovered it? Well, the lead name on the paper published in Physical Review Letters is Yuri Oganessian (for whom element 118 was named), but have a look at that paper and you’ll see there’s a list of over 30 names, and that doesn’t even include all the other people who worked in the laboratories, making contributions as part of their daily work.

From five to many…

There’s a story behind every element, and it’s almost always one with a varied cast of characters.

As I said at the start, when we talk about discovering elements, our minds often leap to “who” — but they probably shouldn’t. Scientists really can’t work entirely alone: collaboration and communication are vital aspects of science, because without them everyone would have to start from scratch all the time, and humans would never have got beyond “fire, hot”. As Isaac Newton famously said in a letter in 1675: “If I have seen further it is by standing on the shoulders of giants.”

There’s a story behind every element, and it’s almost always one with a varied cast of characters.

This post was written by with the help of Kit Chapman (so, yes: it’s by Kit and Kat!). Kit’s new book, ‘Superheavy: Making and Breaking the Periodic Table‘, will be published by Bloomsbury Sigma on 13th June.

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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

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)

It’s only fitting to start with number 101 Mendelevium

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

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).

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.

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

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.

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

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!)

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).

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.

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.

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.

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.

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.

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.)

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.

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

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.

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.

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.

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.

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.

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.

Curium is (possibly) the heaviest naturally occurring element (see here: The other possible candidate is plutonium.

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.

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.

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.)

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.

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.

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.

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.

“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.

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.

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.

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.

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).

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.

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.

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.

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.

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

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.

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.

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.

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.

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

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.

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

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.

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.

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.

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.

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).

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

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.

 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.

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

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.

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.

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.

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.

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.

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.

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).

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.

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.

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.

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.

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).

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.

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.

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.

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!

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

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.

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.

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.

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

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.

Moscovium naturally underwent alpha emission and created… Nihonium.

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.

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.

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.

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

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

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.

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

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.

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.

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.

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.

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

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

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

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.

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.

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.

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

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.

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

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

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.

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.

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.

(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.

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.

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.

(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.

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.

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.

(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.

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.

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.

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

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

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

(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.

(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.

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

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
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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Remarkable, reticent ruthenium

Ruthenium is rare transition metal belonging to the platinum group of elements

What shall I write about this week, I wonder… how about, apropos of nothing, the element ruthenium? It is the International Year of the Periodic Table after all; there have to be some element-themed posts, right?

Ruthenium has the atomic number 44 (good number, that) and the symbol Ru. It was officially discovered by Karl Ernst Klaus in 1844 (there it is again) at Kazan State University in Russia.

You might remember from school (or possibly from your jewellery) that platinum is really unreactive. What has this got to do with ruthenium? Well, unreactive metals can be found in nature as actual metal, rather than combined with other elements in ores. But it turns out that early “platinum metal” — used by pre-Columbian Americans — wasn’t pure, but was in fact an alloy of platinum with other metals.

Gottfried Osann discovered ruthenium before Klaus, but gave up his claim.

In 1827 Jöns Berzelius and Gottfried Osann dissolved crude platinum from the Ural Mountains in aqua regia: a 1:3 mixture of nitric acid and hydrochloric acid (we’ve met aqua regia before, in a famous story about Nobel Prize medals). Osann was certain that he’d isolated three new metals, which he named pluranium, ruthenium, and polinium, but Berzelius disagreed, and this caused a long-running dispute between the two scientists.

Osann eventually gave up the argument — which was a shame, because he was right. In 1844 Karl Ernst Klaus analysed the compounds prepared by Osann and showed that they did, in fact, contain ruthenium.

Klaus had been studying the insoluble residues left over after platinum extraction from Ural placer deposits. Like many chemists at the time, he tasted and smelled the substances he prepared, and he reported that the ammines of ruthenium had a more caustic taste than alkalis, while the taste of osmium tetroxide was “acute pepper-like” (do not try this at home).

He communicated his discoveries to the Academy of Sciences at St. Petersburg and to Academician G. I. Gess, who reported them on September 13th and October 25th, 1844. Klaus named the new element from the Latin word, Ruthenia, and mentioned Osann’s work, saying:

“I named the new body, in honour of my Motherland, ruthenium. I had every right to call it by this name because Mr. Osann relinquished his ruthenium and the word does not yet exist in chemistry”

ruthenium chloride is sometimes shown as red, but it’s actually black

Klaus died of pneumonia in 1864, and the study of ruthenium in Russia more or less stopped for the best part of seventy years, not restarting until the 1930s. The element is now known to harden platinum and palladium alloys, and is used in electrical contacts as a result. When just 0.1% is added to titanium it forms an extremely corrosion-resistant alloy which is particularly useful in seawater environments.

Ruthenium and its compounds have lots of other uses, too, including cancer treatments and in catalysis. Ruthenium(VIII) oxide, a colourless liquid (just: its melting point is 25 oC) forms brown-black ruthenium dioxide in contact with fatty oils; because of this property it’s used in forensics to expose latent fingerprints.

This Swarovski necklace has been plated with ruthenium

One of the most vibrant ruthenium compounds is the dye, “ruthenium red”, which has been used as a biological stain for over 100 years. It has the complicated formula [Ru3O2(NH3)14]Cl6 and is made by reacting ruthenium trichloride with ammonia in air, which might explain why pictures of ruthenium trichloride sometimes show a red substance, when it’s actually a rather boring black.

One place where you might have come across ruthenium in everyday life is jewellery: the metal’s hardness, high corrosion resistance and unusual, not-quite-metallic grey-black finish make it popular choice. Pure ruthenium is expensive though, so it’s almost always plated onto a cheaper base metal.

And now, one last picture to mark my ruthenium-day: check out my fabulous chemistry-themed birthday cake (thanks, Mum!), made by the Cotswold Cake Room. How amazing is this?

Normally at the end of my blog posts I link to my ko-fi account, but this time, instead, if you’re feeling generous please consider donating to my birthday fundraiser to raise money for Alzheimer’s Research UK.

The fundraiser is running through Facebook, which I appreciate doesn’t suit everyone — if you’d like to donate without going via that particular social network, there’s a link to donate directly here. Do drop me a comment below if you do, so that I can say thank you x

Like the Chronicle Flask’s Facebook page for regular updates, or follow @chronicleflask on Twitter. Content is © Kat Day 2019. You may share or link to anything here, but you must reference this site if you do.

2019: The Year of the Periodic Table

The Periodic Table

2019 is the International Year of the Periodic Table

In case you missed it, 2019 is officially the International Year of the Periodic Table, marking 150 years since Dmitri Mendeleev discovered the “Periodic System”.

Well, this is a chemistry blog, so it would be pretty remiss not to say something about that, wouldn’t it? So, here’s a really quick summary of how we got to the periodic table we all know and love…

Around 400 BCE, the Greek philosopher Democritus (along with a couple of others) suggested that everything was composed of indivisible particles, which he called “atoms” (from the Greek atomos). The term ‘elements’ (stoicheia) was first used around 360 BCE by Plato, although at that time he believed matter to be made up of tiny units of fire, air, water and earth.

Skipping over a few centuries of pursuing what was, we know now, a bit of a dead-end in terms of the whole earth, air, fire and water thing, in 1661, Robert Boyle was probably the first to state that elements were the building blocks of matter and were irreducible but, and this was the crucial bit, that we didn’t know what all the elements were, or even how many there might be.

Antoine Lavoisier wrote one of the first lists of chemical elements.

Antoine Lavoisier (yep, him again) wrote one of the first lists of chemical elements, in his 1789 Elements of Chemistry. He listed 33 of them, including some that turned out not to be elements, such as light.

Things moved on pretty quickly after that. Just thirty years later, Jöns Jakob Berzelius had worked out the atomic weights for 45 of the 49 elements that were known at that point.

So it was that by the 1810s, chemists knew of 50 or so chemical elements, and had atomic weights for most of them. It was becoming clear that more elements were going to turn up, and the big question became: how do we organise this ever-increasing list? It was a tricky problem. Imagine trying to put together a jigsaw puzzle where two-thirds of the pieces are missing, there’s no picture on the box, and a few pieces have been tossed in from other puzzles for good measure.

Enter Johann Döbereiner, who in 1817 noticed that there were patterns in certain groups of elements, which he called triads. For example, he spotted that lithium, sodium and potassium behaved in similar ways, and realised that if you worked out the average atomic mass of lithium and potassium, you got a value that was close to that of sodium’s. At the time he could only find a few triads like this, but it was enough to suggest that there must be some sort of structure underlying the list of elements.

In 1826 Jean-Baptiste Dumas (why do all these chemists have first names starting with J?) perfected a method for measuring vapour densities, and worked out new atomic mass values for 30 elements. He also set the value for hydrogen at 1, in other words, placing hydrogen as the “first” element.

Newland’s table of the elements had “periods” going down and “groups” going across, but otherwise looks quite familiar.

Next up was John Newlands (another J!), who published his “Law of Octaves” in 1865. Arranging the elements in order of atomic mass, he noticed that properties seemed to be repeating in groups of eight. His rows and columns were reversed compared to what we use today — he had groups going across, and periods going down — but apart from that the arrangement he ended up with is decidedly familiar. Other chemists, though, didn’t appreciate the musical reference, and didn’t take Newlands very seriously.

Which brings us, finally, to Dmitri Mendeleev (various other spellings of his name exist, including Dmitry Mendeleyev, but Dmitri Mendeleev seems to be the most accepted one). His early life history is a movie-worthy story (I won’t go into that else we’ll be here all day, but check it out, it’s really quite amazing). When he was just 35 he made a formal presentation to the Russian Chemical Society, titled The Dependence between the Properties of the Atomic Weights of the Elements, which made a number of important points. He noted, as Newlands had already suggested, that there were repeating patterns in the elements, or periodicity, and that there did indeed seem to be connections between sequences of atomic weights and chemical properties.

Dmitri Mendeleev suggested there were many elements yet to be discovered.

Most famously, Mendeleev suggested that there were many elements yet to be discovered, and he even went so far as to predict the properties of some of them. For example, he said there would be an element with similar properties to silicon with an atomic weight of 70, which he called ekasilicon. The element was duly discovered, in 1886 by Clemens Winkler, and named germanium, in honor of Germany: Winkler’s homeland. Germanium turns out to have an atomic mass of 72.6.

Mendeleev also predicted the existence of gallium, which he named ekaaluminium, and predicted, amongst other things, that it would have an atomic weight of 68 and a density of 5.9 g/cm3. When the element was duly discovered by the French chemist Paul Emile Lecoq de Boisbaudran, he first determined its density to be 4.7 g/cm3. Mendeleev was so sure of his prediction that he wrote to Lecoq and told him to check again. It turned out that Mendeleev was right: gallium’s density is actually 5.9 g/cm3 (and its atomic weight is 69.7).

Despite constructing the one thing that every chemist over the last 150 years has spent years of their life poring over, Mendeleev was never awarded the Nobel Prize for Chemistry. He was nominated in 1906, but the story goes that Svante Arrhenius — who had a lot of influence in the Royal Swedish Academy of Sciences — held a grudge against Mendeleev because he’d been critical of Arrhenius’s dissociation theory, and argued that the periodic system had been around for far too long by 1906 to be recognised for the prize. Instead, the Academy awarded the Nobel to Henri Moissan, for his work on isolating fluorine from its compounds (no doubt impressive, not to mention dangerous, chemistry).

Henry Moseley

Henry Moseley proposed that atomic number was equal to the number of protons in the nucleus of an atom.

Mendeleev died in 1907 at the age of 72, just before the discovery of the proton and Henry Moseley’s work, in 1913, which proposed that the atomic numbers of elements should be equal to the number of positive charges (protons) they contained in their nuclei. This discovery would have pleased Mendeleev, who had already suggested, based on their properties, that some elements shouldn’t be placed in the periodic table strictly in order of atomic weight.

After which, of course, came the discovery of the neutron — which would finally clear up the whole atomic mass/atomic number thing — atomic orbital theory, and the discovery of super-heavy elements. The most recent additions to the modern periodic table were the official names, in 2016, of the final four elements of period 7: nihonium (113), moscovium (115), tennessine (117) and oganesson (118).

Which brings us up to date. For now…

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The Chronicles of the Chronicle Flask: 2018

As has become traditional, I’m finishing off this year with a round-up of 2018’s posts. It’s been a good year: a few health scares which turned out to be nothing much to worry about, one which turned out to be a genuine danger, a couple of cool experiments and some spectacular shiny balls. So without further ado, here we go…

Things were a bit hectic at the start of this year (fiction writing was happening) and as a result January was quiet on the blog. But not on the Facebook page, where I posted a couple of general reminders about the silliness of alkaline diets which absolutely exploded, achieving some 4,000 shares and a reach (so Facebook tells me anyway) of over half a million people. Wow. And then I posted a funny thing about laundry symbols which went almost as wild. It’s a strange world.

February featured BPA: an additive in many plastics.

In February I wrote a piece about BPA (Bisphenol A), which was the chemical scare of the day. There’s always one around January/February time. It’s our penance for daring to enjoy Christmas. Anyway, BPA is a chemical in many plastics, and of course plastic waste had become – and remains – a hot topic. BPA is also used in a number of other things, not least the heat sensitive paper used to produce some shopping receipts. It’s not a harmless substance by any means, but it won’t surprise anyone to learn that the risks had, as is usually the case, been massively overstated. In a report, the European Food Safety Authority said that the health concern for BPA is low at their estimated levels of exposure. In other words, unless you’re actually working with it – in which case you should have received safety training – there’s no need to be concerned.

In March I recorded an episode for the A Dash of Science podcast, and I went on to write a post about VARD, which stands for Verify, Author, Reasonableness and Date. It’s my quick and easy way of fact-checking online information – an increasingly important skill these days. Check out the post for more info.

April ended up being all about dairy and vitamin D.

April was all about dairy after a flare-up on Twitter on the topic, and went on to talk about vitamin D. The bottom line is that everyone in the UK should be taking a small vitamin D supplement between about October and March, because northern Europeans simply can’t make vitamin Din their skin during these months (well, unless they travel nearer to the equator), and it’s not a nutrient we can easily get from our food. Are you taking yours?

May featured fish tanks, following a widely reported story about a fish-owner who cleaned out his tank and managed to release a deadly toxin that poisoned his entire family. Whoops. It turns that this was, and is, a real risk – so if you keep fish and you’ve never heard of this before, do have a read!

In June I wrote about strawberries, and did a neat experiment to show that strawberries could be used to make pH indicator. Who knew? You do, now! Check it out if you’re looking for some chemistry to amuse yourself over the holidays (I mean, who isn’t?). Did you know you can make indicators from the leaves of Christmas poinsettia plants, too?

Slime turned up again in July. And December. And will probably keep on rearing its slimy head.

July brought a subject which has turned up again recently: slime. I wrote about slime in 2017, too. It’s the gift that keeps on giving. This time it flared up because the consumer magazine and organisation Which? kept promoting research that, they claimed, showed that slime toys contain dangerous levels of borax. It’s all rather questionable, since it’s not really clear which safety guidelines they’re applying and whether they’re appropriate for slime toys. Plus, the limits that I was able to find are migration limits. In other words, it’s not appropriate to measure the total borax content of the slime and declare it dangerous – they should be looking at the amount of borax which is absorbed during normal use. Unless your child is eating slime (don’t let them do that), they’re never going to absorb enough borax to do them any harm. In other words, it’s a storm in a slimepot.

August was all about carbon dioxide, after a heatwave spread across Europe and there was, bizarrely, a carbon dioxide shortage which had an impact on all sorts of things from fizzy drinks to online shopping deliveries. It ended up being a long-ish post which spanned everything from the formation of the Earth, the discovery of carbon dioxide, fertilisers and environmental concerns.

September featured shiny, silver balls.

In September I turned my attention to a chemical reaction which is still to this day used to coat the inside of glass decorations with a thin layer of reflective silver, and has connections with biochemistry, physics and astronomy. Check it out for some pretty pictures of silver balls, and my silver nitrate-stained fingers.

In October I was lucky enough to go on a ‘fungi forage’ and so, naturally, I ended up writing all about mushrooms. Did you know that a certain type of mushroom can be used to make writing ink? Or that some mushrooms change colour when they’re damaged? No? You should go back and read that post, then! (And going back to April for a moment, certain mushrooms are one of the few sources of vitamin D.)

Finally, November ended up being all about water, marking the 235th anniversary of the day that Antoine Lavoisier formally declared water to be a compound. It went into the history of water, how it was proven to have the formula H2O, and I even did an experiment to split water into hydrogen and oxygen in my kitchen – did you know that was possible? It is!

As December neared, the research for my water piece led me to suggest to Andy Brunning of Compound Interest that this year’s Chemistry Advent might feature scientists from the last 24 decades of chemistry, starting in the 1780s (with Lavoisier and Paulze) and moving forward to the current day. This turned out to be a fantastic project, featuring lots of familiar and not quite so-familiar scientists. Do have a look if you didn’t follow along during December.

And that’s it for this year. I hope it’s been a good one for all my readers, and I wish you peace and prosperity in 2019! Suggestions for the traditional January Health Scare, anyone? (Let’s hope it’s not slime again, I’m getting really tired of that one now…)

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What is Water? The Element that Became a Compound

November 2018 marks the 235th anniversary of the day when Antoine Lavoisier proved water to be a compound, rather than an element.

I’m a few days late at the time of writing, but November 12th 2018 was the 235th anniversary of an important discovery. It was the day, in 1783, that Antoine Lavoisier formally declared water to be a compound, not an element.

235 years seems like an awfully long time, probably so long ago that no one knew anything very much. Practically still eye of newt, tongue of bat and leeches for everyone, right? Well, not quite. In fact, there was some nifty science and engineering going on at the time. It was the year that Jean-François Pilâtre de Rozier and François Laurent made the first untethered hot air balloon flight, for example. And chemistry was moving on swiftly: lots of elements had been isolated, including oxygen (1771, by Carl Wilhelm Scheele) and hydrogen (officially by Henry Cavendish in 1766, although others had observed it before he did).

Cavendish had reported that hydrogen produced water when it reacted with oxygen (known then as inflammable air and dephlogisticated air, respectively), and others had carried out similar experiments. However, at the time most chemists favoured phlogiston theory (hence the names) and tried to interpret and explain their results accordingly. Phlogiston theory was the idea that anything which burned contained a fire-like element called phlogiston, which was then “lost” when the substance burned and became “dephlogisticated”.

Cavendish, in particular, explained the fact that inflammable air (hydrogen) left droplets of “dew” behind when it burned in “common air” (the stuff in the room) in terms of phlogiston, by suggesting that water was present in each of the two airs before ignition.

Antoine-Laurent Lavoisier proved that water was a compound. (Line engraving by Louis Jean Desire Delaistre, after a design by Julien Leopold Boilly.)

Lavoisier was very much against phlogiston theory. He carried out experiments in closed vessels with enormous precision, going to great lengths to prove that many substances actually became heavier when they burned and not, as phlogiston theory would have it, lighter. In fact, it’s Lavoisier we have to thank for the names “hydrogen” and “oxygen”. Hydrogen is Greek for “water-former”, whilst oxygen means “acid former”.

When, in June 1783, Lavoisier found out about Cavendish’s experiment he immediately reacted oxygen with hydrogen to produce “water in a very pure state” and prove that the mass of the water which formed was equal to the combined masses of the hydrogen and oxygen he started with.

He then went on to decompose water into oxygen and hydrogen by heating a mixture of water and iron filings. The oxygen that formed combined with the iron to form iron oxide, and he collected the hydrogen gas over mercury. Thanks to his careful measurements, Lavoisier was able to demonstrate that the increased mass of the iron filings plus the mass of the collected gas was, again, equal to the mass of the water he had started with.

Water is a compound of hydrogen and oxygen, with the formula H2O.

There were still arguments, of course (there always are), but phlogiston theory was essentially doomed. Water was a compound, made of two elements, and the process of combustion was nothing more mysterious than elements combining in different ways.

As an aside, Scottish chemist Elizabeth Fulhame deserves a mention at this point. Just a few years after Lavoisier she went on to demonstrate through experiment that many oxidation reactions occur only in the presence of water, but the water is regenerated at the end of the reaction. She is credited today as the chemist who invented the concept of catalysis. (Which is a pretty important concept in chemistry, and yet her name never seems to come up…)

Anyway, proving water’s composition becomes a lot simpler when you have a ready supply of electricity. The first scientist to formally demonstrate this was William Nicholson, in 1800. He discovered that when leads from a battery are placed in water, the water breaks up to form hydrogen and oxygen bubbles, which can be collected separately at the submerged ends of the wires. This is the process we now know as electrolysis.

You can easily carry out the electrolysis of water at home.

In fact, this is a really easy (and safe, I promise!) experiment to do yourself, at home. I did it myself, using an empty TicTac box, two drawing pins, a 9V battery and a bit of baking soda (sodium hydrogencarbonate) dissolved in water – you need this because water on its own is a poor conductor.

The drawing pins are pushed through the bottom of the plastic box, the box is filled with the solution, and then it’s balanced on the terminals of the battery. I’ve used some small test tubes here to collect the gases, but you’ll be able to see the bubbles without them.

Bubbles start to appear immediately. I left mine for about an hour and a half, at which point the test tube on the negative terminal (the cathode) was completely full of gas, which produced a very satisfying squeaky pop when I placed it over a flame.

The positive electrode (the anode) ended up completely covered in what I’m pretty sure is a precipitate of iron hydroxide (the drawing pins presumably being plated steel), which meant that very little oxygen was produced after the first couple of minutes. This is why in proper electrolysis experiments inert graphite or, even better, platinum, electrodes are used. If you do that, you’ll get a 1:2 ratio by volume of oxygen to hydrogen, thus proving water’s formula (H2O) as well.

So there we have it: water is a compound, and not an element. And if you’d like to amuse everyone around the Christmas dinner table, you can prove it with a 9V battery and some drawing pins. Just don’t nick the battery out of your little brother’s favourite toy, okay? (Or, if you do, don’t tell him it was my idea.)

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