Articles by: Mark

The chrome plated mystery of the Terracotta army’s swords



QIMG_6487in the 1st Emperor of China prepared well for the after-life. Throughout his reign he commissioned and built an eternal army of some 6000 soldiers, charioteers and cavalry. The  warriors stood in formation, buried at the foot of his tomb, there to guard the Emperor for eternity.

But all did not go as planned. Shortly after Qin was entombed chaos descended on his newly united China. Qin’s heirs, wishing to defeat him (even after his death) attacked his after-life defences. History tells that the underground barracks that housed the vast army of terracotta warriors were set alight. Fires smouldered for 90 days, structures around the ornate statues collapsed smashing the exquisite army. The broken soldiers and their bronze weaponry lay buried in ash and rubble. The great mausoleum was forgotten. Two millennia passed. Until in 1974, a peasant farmer, whilst digging a well, found fragments of a crushed warrior. And excavations began.

The thousands of individual Qin dynasty soldiers, have been painstakingly pieced together and placed back in formation. They are an awe inspiring sight. But I marvelled just as much when I saw no less incredible bronze weapons that armed the officers. Their swords are still sharp and largely unaffected by the 2200 years that have passed since they were forged. Instead of the green corrosion you’d expect on bronze artefacts the blades actually appear gun metal grey. Why this is the case is something of a mystery.
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There are reports of an analysis of the artefacts conducted by the Chinese Research Institute of Nonferrous Metals and Chinese Academy of Geological Sciences (although I am unable to find the primary data). The suggestions is that a 10-15 micron coating containing chromium oxide (at up to 2% chromium) was found. The conclusion; for millennia this thin layer protected objects from the ravages of time and chemistry.

So where did the chromium oxide layer come from? Did the ancient Chinese metallurgists, as suggested by curators of the Terracotta army, really have chrome plating technologies thousands of years before it was developed in the west? Over the intervening time did the chromium shine lose its lustre as it slowly oxidised, resulting in the grey we see today? Is a 10 micron, dilute layer of chromium oxide really enough to impart anti-corrosion properties?  Or is there another explanation for the immaculate swords?

This isn’t the first time someone’s asked these questions. Its been discussed on a sword forum where suggestions include forgeries and serendipitous impurities in the alloy. The latter seems to be supported by Prof Frank Walsh, an electrochemist now at Southampton University, when he was interviewed for an ABC documentary back in 2003 where:

Professor Walsh notes that the heat from the fires and the presence of carbon would have provided a reducing environment in which chromium atoms could have migrated to the surface of the weapons. There they’d oxidise and form a protective coating … Metals do diffuse over time, so this ‘natural’ explanation is plausible.

For me this isn’t a totally satisfying explanation. Largely since it appears, from the items on display, that only the blade is free of corrosion. The hilt has clearly corroded. If the slow migration of chromium to the surface of the blade is responsible why didn’t this mechanism occur elsewhere on the swords? But the idea that Qin’s weapon smiths knew how to apply anti-corrosion layers to their creations seems rather fanciful.

Which leaves the above questions unanswered. So chemists, time to reopen discussions. What do you think is going on? Can anyone come up with a way that the ancient Chinese might have deliberately or accidentally protected the weapons?  Or what else might have resulted a corrosion free blade, whilst the rest of the weapon is tarnished?

P.S. Any Chinese chemists/metallurgists out there who might be able to track down the analysis of the blades?

By September 22, 2015 12 comments Uncategorized

How science lost one of its greatest minds in the trenches of Gallipoli



August 10, 1915. The Gallipoli sun beats down on the back of a Turkish sharpshooter. He is patient and used to the discomfort. He wipes the sweat from his eyes and peers back down the sight of his rifle, sweeping back and forth across the enemy lines. He’s hoping to spot a target worth taking a shot at as each muzzle flash risks giving his position away.

His sight settles on the shoulder pip of a second lieutenant. The target bends down out of sight, then reappears, now with a phone at his ear. He stands still as he sends his dispatch. It’s an easy shot for the sniper. He squeezes the trigger and yet another young man dies.

Infantry from the British Royal Naval Division in training during the Battle of Gallipoli.
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The Turkish soldier settles down in his hole, pleased with his marksmanship. He wonders if he’s made a significant difference to the war effort (probably not).

However, he may well have caused the single most costly death of the entire war. His victim, now lying in a trench on a peninsula in Turkey, is 27-year-old Henry Moseley. The loss to science is incalculable.

Hidden patterns

Despite his young age, Moseley had already made a stunning contribution to chemistry and physics. It is thanks to him that that the periodic table looks the way it does today.

He had graduated from Oxford just five years before his death. Immediately after graduating he was employed as a teaching assistant by the great physicist Ernest Rutherford in Manchester. Moseley hated it, describing his duties as “teaching elements to idiots” and his students as “mostly stupid”. His real passion was research, so in his spare time he used his energies to set up his experiments.

Moseley was working in an era of physics that was concerned with the power of X-rays. The Braggs, a father-son team working in Leeds, were developing X-ray crystallography. This allowed science to probe the atomic structure of molecules.

But instead of jumping on that bandwagon – shining X-rays at crystals to work out chemical structures – Moseley turned his attention to the elements themselves. He studied the X-rays the elements gave off when bombarded with electrons. His results had major implications for the famous periodic table in which elements are presented.

Back in 1869, Dimitri Mendeleev arranged the elements in a logical fashion. He ordered them by weight and then laid them out in a table. Next he shuffled the dimensions of his table to take similarities of elements into account. For example, lithium, sodium and potassium have similar chemical properties and were arranged in one group on a line of the table (modern tables have been flipped so that these groups are now in columns).

Mendeleev’s periodic system.
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Likewise for fluorine, chlorine, bromine and iodine. And so the periodic table was born. The elements were now arranged in a clear sequence – and each was given an atomic number denoting its position in that sequence. But there were a few problems, some elements didn’t quite fit the order. Their behaviour suggested one position in the table, but their atomic weight put them somewhere else. So the atomic weight and atomic number of the elements didn’t quite correlate.

In Manchester, and later in Oxford, Moseley took samples of all known elements, from aluminium to gold, and measured the X-rays they gave off after bombarding them with electrons. He discovered that each element emitted a distinct frequency of X-rays, and that this frequency correlated with the atomic numbers. When he plotted the square root of the frequency, against the atomic number everything fell into straight lines on his graph.

For the first time it became clear that an element’s atomic number, corresponding to its position on the table, had a basis in physics and was not merely a convenient label. And that these numbers (confirmed by Moseley’s measurements) resolved the previous issues with the periodic table. He also noted points missing from his graph and surmised that these gaps must be due to yet-to-be discovered elements. It was wasn’t until 30 years after his death that that the last of Moseley’s missing elements were discovered.

Nobel effort

Moseley’s achieved all this in a research career lasting just 40 months. At the outbreak of war in 1914 he signed up, becoming a signalling officer in the Royal Engineers. Had he survived, it is likely he would have been awarded the 1916 Nobel Prize in Physics (as it was no Nobel Prize in Physics was awarded that year). There is no telling what other breakthroughs might have been achieved in the alternative history in which he survived the war.

There is one more legacy that Moseley left. His death raised the question of whether great minds such as his should really be risked on the battle field. Despite the war, the international scientific community was outraged at the loss of such a renowned scientist, who still had so much to offer.

From then on scientists were used in a very different way in wars. For better or worse scientists in the next great war developed penicillin, radar, programmable computers and, of course, the Manhattan project. All these inventions had much greater impacts on World War II than any of the individuals involved could have made at the front line.

The Conversation

Mark Lorch is Senior Lecturer in Biological Chemistry at University of Hull.

This article was originally published on The Conversation. Read the original article.

By August 10, 2015 2 comments Uncategorized

Spread the word about chemistry & don’t fret the chemophobia

   

At times chemists can feel rather maligned. But according to the RSC’s study of the UK public’s perceptions of chemistry we shouldn’t be quite so worried about what people think of us.  We do however need to get out there and let people know what we do.

The other sciences seem to get pride of place in the medias science pages and TV shows. Whilst chemistry has no celebrity singing it’s praises, not a single chemist made it into Science Magazines  50 science stars on Twitter, and chemistry news just doesn’t get the same coverage as the big physics projects (even when the physics project was all about landing a chemistry lab on a comet).

As a profession we think we do some pretty important work. After all every modern pharmaceutical, synthetic material, cleaning product, fuel, battery, ink and electronic device contains our handy work. Which is why we get upset when an advertising campaign emblazons the dreaded words “Chemical-free’ across some product or another.  Or the likes of The Food Babe, decides to start an uniformed campaign against an additive based on little more than the fact she can’t pronounce it.

Sometimes we (I) throw our toys about the pram and start ranting about how everything is made of chemicals and how chemophobia is rife. God knows bloggers have written enough posts about it, including a comical ‘paper’ in Nature Chemistry. However, we should settle down, because the Royal Society of Chemistry has commissioned a comprehensive study of UK public’s perceptions of chemistry, chemists and chemicals. And it seems many of those (mine included) irate blog posts got it wrong.

I’ve been able cogitate about what it all means as I got an an advanced copy of the findings and have had time to discuss them with the RSC. So here’s my potted summary and a few conclusions.

Perceptions of perceptions of chemistry: First off the RSC asked it’s members about how they thought the public perceived chemistry. And sure enough most expected a negative attitude. The fear of chemophobia amongst chemists was certainly commonplace. But when the RSC turned to the public chemophobia didn’t materialise in anywhere near the expected levels. Instead …

Perceptions of chemicals:Chemophobia is not commonplace. Less than 20% of the public thought that all chemicals are dangerous or harmful. Most people really didn’t have strong feelings about chemicals one way or another. And 60% knew that everything is made of chemicals. This is despite the use of ‘chemical’ to mean something dangerous being very common.

Perceptions of chemistry: Here 59% believe the benefits of chemistry are greater than any harmful effects (as compared to 55% for science). And once again most people were pretty neutral about chemistry as a subject.

Perceptions of chemists: It turns out people just don’t know what we do. This is made all the worse, in the UK, by retail pharmacists being universally known as chemists.

Don’t fret the chemophobia

There’s an important message here about what’s going on when ‘chemical’ is used pejoratively. For most people ‘chemical’ has a double meaning. So we shouldn’t get upset when ‘chemical’ is used as a short hand for toxin or poison. I know I’ve written plenty that’s contrary to this, but the RSC’s study has really changed my thinking. People are quite capable of holding two meanings of ‘chemical’ in their minds and we should just try and ignore the use of the one that soooooo grates. In fact it may even be counter productive to try and combat our perceived misuse of ‘chemicals’. As the RSC study puts it…

“People’s views of chemicals do not impact their view of chemistry or chemists. But if chemists talk about chemicals all the time, especially in trying to combat inaccuracies in the views of others – we risk activating existing fears.”

Chemists aren’t being tarnished with the chemicals = danger association. But by continually banging on about how chemicals are in everything we run the risk of being alienating our audience. Luke Gammon put’s it very well.

Don’t denigrate, belittle or “punch-down” – remember to laugh with, not at – lest we lose the battle for the public perception of “chemicals”.

So here’s me hanging up my #chemophobia hash-tag. And conceding that Luke, Renee and Chemtacular probably had the right idea (check our their blogversation)

There’s a void we need to fill

However the overwhelming message is that there is a void in the public’s perceptions of what it is we do. And it’s a gap that we should all do our best to fill. That means that we all need to do our bit, whether on social media, in blogs or even at parties. We can all tell people about what we do. There’s a great appetite for science out there, we shouldn’t assume that people aren’t interested in what chemists get up too and we certainly shouldn’t fear a negative reaction from them.

To go along with the study the RSC have also published a communications toolkit which summaries their main findings and contains some tips for how to get the wonders of chemistry across. Please go and take a look and then spread the word.

And join in the discussion on twitter with the hash-tag #chemperceptions.