The Standing Invitation

Archive for October 2011

The Smell of Money

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There really is nothing quite like writing a doctoral thesis for increasing your interest in things other than your thesis. Today I wondered: why do some metals have a smell?

Go through your small change right now. The pennies have a distinct metallic smell. But how can this be?

In order to smell something, particles of it have to get to your nose. This is easily understandable with liquids, because all liquids are continuously shedding molecules to the air around them through the process of evaporation. The tendency of a liquid to release gas by evaporation is given by its vapour pressure, which varies with temperature: the higher the temperature, the higher the vapour pressure, faster the liquid evaporates.

Solids, on the other hand, do not evaporate in this way, although there is an analogous process called sublimation, in which particles leave the solid’s surface as gas without passing through a liquid state. This means that solids do have vapour pressures, but these are extremely low for things like metal coins, which do not have a noticeable tendency to evaporate when left on the pavement on a hot day.

So what is it about coins that gives them this smell of metal? Marvellously, there is a paper in Angewandte Chemie from 2006 that answers exactly this question. The authors focus on iron, which is often described as having a ‘musty’ aroma. What they find is that iron is in fact odourless, both as a solid lump of metal and as a solution.

They are unable to resist the pun: “Ironically, the iron odour on skin contact is a type of human body odour.”

The experiments involved the sweat and blood of researchers. Sweat is corrosive: it attacks the surface of the metal and partially dissolves it, forming small amount of the ion Fe2+. This is reacts within seconds with oxygen give to Fe3+, but also causes a reaction with the sweat itself. Lipidperoxides occurring naturally in sweat are  broken down into volatile carbonyl hydrocarbons that we are able to smell. Metal smells, but only because it has been touched by people.

The same mechanism explains the metallic smell of blood – one of the researchers’ own blood was used in the experiment, apparently. Blood contains iron, which decomposes lipidperoxides in the blood.

The typical “musty” metallic odor of iron metal touching skin (epidermis) is caused by volatile carbonyl compounds (aldehydes, ketones) produced through the reaction of skin peroxides with ferrous ions (Fe2+) that are formed in the sweat-mediated corrosion of iron. Fe2+ ion containing metal surfaces, rust, drinking water, blood etc., but also copper and brass, give rise to a similar odor on contact with the skin. The human ability to detect this odor is probably a result of the evolutionarily developed but largely dormant ability to smell blood (“blood scent”).

It’s a nice everyday example of the scientific problem of correlation implying causation. You might describe the smell as ‘metallic’, but that’s only because you only smell it around metals. In reality, the metal is not what you’re smelling; you’re smelling the decomposition of chemicals produced by your own skin.

In reality, the copper coins you’ve been sniffing have a smell we call ‘coppery’ because they are smeared with the chemically decomposed sweat and oils from the hundreds of greasy, sweaty fingers that have touched them. A lovely thought, isn’t it?


Written by The S I

October 31, 2011 at 11:59 pm

Arrogance and Respect

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Is it always arrogant to tell people they are wrong?

Arrogance is a common accusation levied at scientists when they declare that, actually, x is the case, and anyone who believes otherwise is simply incorrect. And, yes, there is an arrogance associated with any kind of absolute certainty, since there is very little, if anything, of which anyone can be truly certain. This is something that scientists know (or should know) better than anyone. Scientists are generally very candid about what they do not know, where their areas of expertise are and what lies outside it, and their claims are always tempered by error bars, confidence levels, and the fact that correlation does not imply causation; and that’s before you get down to the real philosophy of science stuff with the problem of induction, unreliability of the evidence of senses and so on.

Nevertheless, there are some things about which scientists’ feelings come so close to certainty that there isn’t much reason calling it anything else – certainty in the existence of atoms, or that the Earth is an oblate spheroid orbiting a main-sequence star, or that humans and broccoli share a common ancestor. The evidence of these things is overwhelmingly good, and anyone who believes otherwise is wrong.

But is it arrogant to say so?

The concept of arrogance is bound inextricably to the idea of respect: to be arrogant is to not respect another person’s opinions.

Now I’m just going to come right out and say it: some people’s opinions are pretty dumb. The idea that the Earth is 6000 years old deserves no respect whatsoever. But then, neither does the idea that the Earth is 4.5 billions years old. No opinion deserves respect, or protection from criticism.

But is disrespecting an opinion the same as disrespecting the person who holds it? Sometimes, if it’s not done properly. And here lies the meaning of arrogance.

Respect, as applied to an intellectual, means that, if this person says something that is totally opposed to your own opinions, you still listen to hear what she has to say. It’s tempting to dismiss people who say that trial by jury should be abandoned; but when Richard Dawkins says it, I sit up and pay attention, because I know he’s thought hard about it. I respect the man, and so I listen.

To respect someone means to assume that his opinion is founded on careful thought that is worth taking on board; it also means to assume that he is amenable to rational argument, and is not so inflexible that he cannot be persuaded otherwise, if he is wrong. One should always make this assumption, and frame one’s arguments as though to someone who will listen to them; if nothing else, it is good exercise. To treat one’s opponent as unreachable by logical discourse is arrogant in the extreme.

So next time you see a conversation in which one debater calls the other arrogant, ask yourself this question: who is showing the least respect? The one who is hears a deeply-held belief and demands evidence for it? Or the one who’s deploying the A-word as a get-out-of-argument-free card and hoping to stop the debate in its tracks?


Actually, Dawkins makes good points about trial by jury. Worth reading.

Written by The S I

October 29, 2011 at 11:59 pm

Chemistry in 1911 Was Just Adorable

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What was the cutting edge of chemical research a century ago? Fortunately the Journal of the American Chemical Society stores PDFs of papers published as early as 1879. What was contained in the issue from one hundred years ago this month?

The paper that stands out for me is by Otto Folin and Fred F Flanders, and is called simply The Determination of Benzoic Acid. I find it adorable beyond words.

Benzoic acid is a simple compound that occurs naturally in many plant and animal species. Extracting it from an aqueous solution is now a common experiment for first-year undergraduates: add a little HCl and a lot of chloroform, and the benzoic acid will migrate to the chloroform layer; then separate the chloroform layer, evaporate off the chloroform and you’ll be left with pure compound. When all you’re doing is getting benzoic acid out of water, it’s almost impossible to get it wrong (although somehow, when I was an undergraduate, I managed…); but if there are a whole bunch of other, similar compounds in the water too, then obtaining the benzoic acid pure is much more difficult.

So Folin and Flanders dedicated themselves to developing techniques for obtaining pure benzoic acid from cranberries (I love this so much). They were able to find the amount of benzoic acid in the chloroform layer directly by measuring the acidity of the solution – an improvement over removing the chloroform by evaporation since, in the days before rotary evaporators, this would have involved just leaving the flask open on a bench for a couple of days.

But cranberries were too easy, they say. They demanded a harder challenge. And so they turned their attention to catchup.

Reading this I had no idea what ‘catchup’ was. It turns out to be an early alternative spelling of ‘ketchup’ (they also spell ‘definite’ and ‘volatile’ without the final e). Catchup is essentially tomatoes preserved by acid: the acid prevents bacterial growth.

Extracting benzoic acid from catchup was made complicated by the presence of these various acids. They tended to end up in the chloroform layer alongside the benzoic acid and needed to be taken care of. Folin and Flanders eventually removed these impurities with carefully pH-controlled aqueous washes; by recording the pH at which each acid came out, they were able to identify many of the acids.

Using this technique they were able to find the amount of benzoic acid in two of the sauces – Snider’s catchup and Heinz’s catchup. Their technique wasn’t perfect – the benzoic acid never came off entirely clean (the impurity was probably the chemically similar cinnamic acid), and wasn’t accurate for levels higher than 0.1%, but as a simple test that only takes 90 minutes and lets you recover the chloroform afterwards, they seem rightly pleased with it.

Rather cute, really, isn’t it?



Original paper:

See the Wikipedia pages for benzoic acid, cinnamic acid, and a surprisingly detailed discussion of the etymology of the word ketchup.

Written by The S I

October 27, 2011 at 11:59 pm

The Good Book

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At the end of the film The Time Machine (the scene does not appear in H G Wells’ original novella), the Time Traveller leaves the present day to spend the rest of his life in the distant future, helping to rebuild the society he has helped to liberate. Before he goes, he takes with him three books from the library, and we are not told what they are. It is an open question directed at the film’s audience: what three books would you take with you?

I’d be tempted to say The Origin of Species. I’d like to get that one absolutely sorted out on day one.

Evolution is a fact. It really, really is. I can just about imagine someone who can look at the overwhelming evidence in its favour and come to some other conclusion; I wouldn’t mind meeting this person, we might talk about it over coffee and an apple danish, it’d be fun. But the existence of people who think that to acknowledge the truth of evolution is a political stance rather than an empirical one truly astonishes me.

And yet people like this do exist. There are countries when a candidate can lose an election for acknowledging that evolution is real, or that climate change is real. Fine, if the objections raised are grounded in facts – but they are not. They have become matters of personal identity, religious orthodoxy and party-political loyalty. To call attention to facts is seen as a personal attack on one’s values. And other people’s values are to be respected, however baseless they are.

What do I ask for, then, in a well-run society? That the veracity of evolution be constitutionally protected?

No. That kind of mindset would only make things worse in the long run.

And this is why, over and above The Origin of Species, I would choose another book. I would find space in my time machine for Mill’s On Liberty. Although Darwin’s book is invaluable for showing us, better than anything else, our true position in the universe, I would argue that On Liberty transcends even this in importance, because it tells us about how to react to theories like Darwin’s.

This book, written in the 1850s, is a brutal attack on anyone who wants to see an idea ­– any idea at all – as being above criticism. It says, beautifully, that the only way of arriving at the truth, or of preventing us forgetting the truths we’ve already uncovered, is by exposing it to constant criticism. Yes, feel free to have your opinions, but be prepared to fight for them. By calling on everyone to attack opinions they do not like – and to defend against attack the ones they hold dear – it casts suspicion on anyone who holds an opinion for any reason other than because they have evidence for it.

The power to criticise ideas – all ideas, held for whatever reason – and to see which ones stand and which ones fall based solely on what the arguments for and against are them are, is a necessary condition for a decent, well-constructed, compassionate society. It might even be a sufficient one.


On Liberty can be found here. Don’t be put off by this man’s egregiously long sentences; his stuff is gold.

Written by The S I

October 25, 2011 at 11:59 pm

Who You March Beside

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I joined my first political protest march in 2009; I confess that while I agreed broadly with its principles, I knew even at the time that I didn’t understand the issues well enough to commit myself fully to it. I was there mostly to see what it was like.

It was not something I enjoyed. I found myself holding a placard that only approximately expressed my views, alongside people I disagreed with politically, chanting slogans I would have phrased very differently. I left after an hour or so feeling not enlivened and proactive, but rather ashamed at having lent support to people and groups whom I dislike.

Any mass political demonstration involves, by definition, a large and probably rather diverse crowd of people. In joining it – joining any movement – one hopes to gain more impact for your cause through strength of numbers; in doing so, one sacrifices individuality. You become part of a crowd. You lend your voice to its demands, and become responsible, in part, for the actions, good or bad, of those you march beside.

This trade-off is inevitable; and now, before joining any protest, I try to get as clear a picture as possible of what I will have to sacrifice, and to whom. As in any exchange, there are instances when the price is worth paying; when the cause is so important that it largely doesn’t matter what nutjobs you have to associate with to get the job done. But there is plenty that a movement can do to make itself more attractive to me as a customer in the free market of political activism.

It is easy to see why protests are often perceived as vehicles of free expression of alternative lifestyles. After all, they are strikes against authority – what better way of showing how little control the Powers have over you than by having a street party? There are rare cases when this is acceptable, such as when the right being defended is exactly the right to have a party. But for the most part it annoys me. It is never good for a movement’s credibility than for it to be seen to be frivolous.

The treatment of all authority as being some monolithic capitalised Authority is always a bad thing. I recently saw, at Occupy London Stock Exchange, a poster about compulsory vaccination causing autism. (It cheered me enormously that it had been vandalised by people signing their names alongside their qualifications in clinical psychology.) The two causes are unrelated; affiliation with one should never entail support of another.

A third thing is the presence of a manifesto. It doesn’t matter if it’s written on soggy cardboard, as long as it’s clearly stated. This goes a long way to mitigating the loss of individuality, because a statement of purpose lets people know exactly what they have signed up for.

It will always be in the interests of the authority protested against to portray the protesters as diffuse, disorganised, violent, unintelligent, and more interested in fun than in change. It is the responsibility of activists to make a pre-emptive strike, and make their motivations clear as a laser, and as serious as politics.

Written by The S I

October 23, 2011 at 11:59 pm


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For this other (regrettably) quick post, I want to introduce you to Mana Neyestani, a magnificent political cartoonist from Iran. His black and white images of democracy and violence combine a deliciously black humour with a fiery rage against the brutality of the government. The colour green is for the movement for democracy in Iran; a grinning Pinocchio is the lying President. But the images of brutality and oppression are timeless and understandable even without translation. Enjoy.

Facebook users can find extensive collections here and here; others will have to make do with the google image search for his stuff, though the viewing is less good.

Written by The S I

October 21, 2011 at 11:59 pm

Posted in Politics

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Fun with Friedman

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This will have to be another brief one because I’m away in parts foreign. For my travel literature I will be reading Mill’s Utilitarianism and probably getting some funny looks for it.

Someone else who I’m sure was a big fan of Mill was Milton Friedman. I’ve been watching a lot of videos of Friedman lately, trying to figure out exactly how I feel about him (I certainly hadn’t expected him to have a sense of humour). Here are some of the good ones on responsibility to the poor, on greed, on corporate responsibility (or lack thereof) and drug legalisation.

Have fun.

Written by The S I

October 19, 2011 at 11:59 pm