Field of Science

A day in pchem lecture: NMR, lululemon yoga pants and tattoos

By lululemon athletica
(Flickr: Yoga Journal Conference)
 [CC BY 2.0], via Wikimedia Commons
It's the end of term, two more 90 minute lectures left in my introductory quantum chemistry and spectroscopy course.  We've done the basics of wave functions and expectation values, we've looked at linear variation theory and written code to do Hückel MO calculations, we've covered rotational and vibrational and rotational-vibrational spectroscopy.  So what to do with these last few days?  The quantum mechanics of NMR.

I kicked off today's lecture by looking at magnetic field strengths, what's the earth's magnetic field (5 μT) or of a refrigerator magnet (5 mT), compared to the superconducting magnets used in NMR, which are on the order of 10T. (1T is one tesla.)  This led to a quick review of the risks in MRI, which aren't about the energy of the radiation used (which is billions of times lower than X-rays), but more about the interactions of the high magnetic fields, the radiofrequencies and metals.

A hand shot up and student who is an EMT describes a patient whose tattoo started burning during an MRI.  I pointed out this is a known phenomenon, and while most inks don't pose an issue, it should discourage you from DIY tattooing.  Then a student asked, "Is it true you can't wear lululemon pants when you have an MRI?"

I admitted this was out of my zone, but promised to follow up.

I can now report that yes, wearing lululemon pants — or any clothing with metallic microfibers, such as those great antimicrobial t-shirts — in an MRI can lead to serious burns, particularly in patients that have been sedated or are otherwise unconscious and unable to signal their discomfort.  Even non-ferromagnetic materials presents problems in the MRI as eddy currents can develop around them, creating little induction heaters.  Loops of all sorts, even skin to skin contact between a patient's own body parts can lead to heating and subsequent burns.  And tattoos with large loops in them?  They can heat as well.

Other things I learned this afternoon.  You can levitate a frog with a 16T field (thank you Wikipedia), and neutron stars have magnetic fields on the megaTesla scale.

Marketing molecular fear

"A woman can recite the most complicated recipe, but how many can name the ingredients in a headache tablet?  If you don't want drugs you know nothing about, take Bufferin...."

This short commercial by actress Joan Fontaine aired in the mid-1960s, an era when Tylenol (acetaminophen) was just gaining market share in the US as a painkiller for adults.  I'm fascinated with the way in which it foreshadows the modern trope of avoiding chemicals you can't pronounce, already marketing the molecular fear that now fuels the largely unregulated, 12 billion dollar a year vitamin and nutritional supplement market in the US.  Rachel Carson's Silent Spring had appeared in 1962, starting a shift towards seeing chemical as a synonym for poison.

Much like the material put out fifty years later by Jospeh Mercola, Dr. Oz and The Food Babe, this ad tacitly assumes people are incapable of understanding science and must rely on experts of some sort.  Who you should not trust.  And women, no matter how competent within their limited domestic sphere, are even less capable.

All natural! Removes burned on food! Magic chemical concoctions

I steamed a batch of dumplings for lunch yesterday, which never had time to cool before being wolfed down by the spring break crowd in my kitchen.  So I pulled another set from the freezer which someone in the scrum popped into the steamer.  In the confusion, no one checked to be sure there was still water in the steamer.  Fast forward eight minutes, the dumplings are stuck to the steamer and the smoke alarm is shrieking.

The dumplings were edible, but the bottom of the pan was pretty badly scorched.  My mathematician spouse wondered if I had some special chemical that would magically clean the pan.  I said I did and that I'd already applied it.  "What did you use?" he said, peering into the blackened pot. "Water."

Water is sometimes called the universal solvent, and though many things will dissolve in water, it's not clear that more things are soluble in water than in any other solvent (or how you would undertake such an inventory). And it's absolutely a chemical, though it is so ubiquitous we have a hard time thinking of it as such.  Even chemists.

The pot soaked overnight, and with the application of a bit of elbow grease (physics, not a chemical) and a finely ground mixture of low volatility chemicals (feldspar, limestone, sodium carbonates with a dash of soap - aka kitchen cleanser) is as shiny as ever.

A universal hotness manifold

Slothful thermometers.
I'm working on a column for Nature Chemistry about temperature, prompted by the incredible collection of early thermometers and thermoscopes at the Museo Galileo in Florence.  (Can't get to Florence and visit it and the amazing gelato spot Perché no! — they have an incredible online virtual tour of the exhibitions.)

The question of how one can be assured that two objects, well separated in space and/or time, would be in thermal equilibrium with each other should they be brought into contact — that is, can you be sure that two objects are at the same temperature —  is not quite as simple as it sounds.

First you need a measuring device, then you need to agree on a way to quantify the output of the device.  And it would be nice if your colleague who lives across an ocean could set up her apparatus in such a way as these quantities are the same.  In another words, you need a calibrated thermometer.

There's a wild and wonderful history to figuring out how to create this basic piece of lab equipment, including what you mean by zero, how big should degrees be, and how to to tell if water is really boiling.  But my favorite find is in a paper by mathematician James Serrin, in which he defines a thermometer by formally stating the zeroth law of thermodynamics [1]:

Manifolds, M, marked in with L, hotness levels (the black
enamel dots).  Or,17th century Florentine degree thermometers.
"There exists a topological line M which serves as a coordinate manifold of material behaviour. The points L of the manifold M are called 'hotness levels', and M is called the 'universal hotness manifold'."

I'm trying to imagine standing up in front of a classroom of students and talking about hotness levels.

And those slothful thermometers?  They tell the temperature by little balls that float or sink...slowly, very slowly.  Lazily, you might say.

Just reading the paper brought back memories, the collection of conference papers this quote is pulled from are reproduced from typed (double-spaced, with a typewriter!) manuscripts, complete with the typos you might expect before word processors and spell check arrived on the scene ("physcis").  In the late 1970's this was one way to inexpensively and rapidly get proceedings and reviews into print.

1.  "The concepts of thermodynamics" in Contemporary Developments in Continuum Mechanics and Partial Differential Equations. Proceedings of the International Symposium on Continuum Mechanics and Partial Differential Equations, Rio de Janeiro, August 1977, edited by G.M. de La Penha, L.A.J. Medeiros, North-Holland, Amsterdam, p. 416.

Weird words of science: scientist

Woman teaching geometry to men
illus. 14th century copy of Euclid's Elements
Scientist may not sound like a weird word, but when it was first coined, it was thought "unpalatable," along with (understandably) "nature-poker." Recently my sister tagged me in a Facebook post linking to a series of articles on women in science. She thought it interesting that the word had been coined to honor the work of a woman in science.
"Not only did Scottish mathematician, science writer, and polymath Mary Fairfax Somerville (December 26, 1780–November 28, 1872) defy the era’s deep-seated bias against women in science, she was the very reason the word “scientist” was coined: When reviewing her seminal second book, On the Connexion of the Physical Sciences, which Somerville wrote at the age of 54, English polymath and Trinity College master William Whewell was so impressed that he thought it rendered the term “men of science” obsolete and warranted a new, more inclusive descriptor to honor Somerville’s contribution to the field." — from Maria Popova and Lisa Congdon's 2013 project The Resurrectionists
Oddly enough, I'd read William Whewell's review of Somerville's On the Connexion of the Physical Sciences while writing an essay about the public conception of scientists, and my recollection was that the coining of scientist, while reported in this review, was not in fact spurred by Somerville's work.  So I went back and read it again.

Whewell was certainly impressed with Somerville and her book, but his tale of the creation of the word 'scientist' makes no mention of honoring Somerville or her contribution.  About the only person Whewell seems impressed with in this context is the "ingenious gentlemen," thought to be himself!
A curious illustration of this result maybe observed in the want of any name by which we can designate the students of the knowledge of the material world collectively. We are informed that this difficulty was felt very oppressively by the members of the British Association for the Advancement of Science, at their meetings at York, Oxford, and Cambridge, in the last three summers. There was no general term by which these gentlemen could describe themselves with reference to their pursuits. Philosophers was felt to be too wide and too lofty a term, and was very properly forbidden them by Mr. Coleridge, both in his capacity of philologer and metaphysician ; savans was rather assuming, besides being French instead of English; some ingenious gentleman proposed that, by analogy with artist, they might form scientist, and added that there could be no scruple in making free with this termination when we have such words as sciolist, economist, and atheist—but this was not generally palatable; others attempted to translate the term by which the members of similar associations in Germany have described themselves, but it was not found easy to discover an English equivalent for natur-forscher. The process of examination which it implies might suggest such undignified compounds as nature-poker, ornature-peeper, for these naturae curiosi; but these were indignantly rejected." [from the Quarterly Review, 1834, emphasis mine]
Interestingly, Wherwell does tackle the issue of women in philosophy/science:  "Our readers cannot have accompanied us so far without repeatedly feeling some admiration rising in their minds, that the work of which we have thus to speak is that of a woman."  It's a fascinating read, in which you can see the threads of imagery that is still current (and still unsupported by data) about the innate differences between the minds of men and women.

And in the end, scientist would catch on, by the early 20th century it was far eclipsed "natural philosopher" as the preferred general term.

Science at Play

The Chemical Heritage Foundation in Philadelphia's latest exhibit is called "Science at Play" — and even if you can't get to Philadelphia, you can browse some of the materials on Tumblr, including animated videos of experiences — good and bad — with chemistry kits.

When my kids were young, I encouraged them to play with science stuff.  I wanted them to be willing to get messy, to make mistakes, to think about stuff where it wasn't perfectly clear what was going on and to begin to understand that protective gear wasn't a ritual or a costume, but part of thinking through how to reduce risk.  That you could make your own equipment.

Though kits have gotten far more tame over the years — no more uranium ore or instructions for making ammonia in your hand — there are still commercial kits that let kids play not only responsibly, but productively, with chemistry.  The new MEL kits that Todd Bookman's piece on chemistry kits for The Pulse (listen here - full disclosure, I was interviewed for this segment) highlights are particularly cool in that they plug into another important skill for budding scientists:  how to share your work.  The kit comes with a lense that you can snap over a cell phone camera, giving you an up close look at what you are doing, and enabling you to share it via social media.

But as important as kits are, I think the ad hoc experiences of doing science are equally critical.  They hone the ability to read instructions (and reveal how much is not revealed in the methods sections of any science communique), encourage a sense of scale and quantitation (how much is 1 gram of something, as opposed to pour in this packet) and help novice scientists get comfortable with tinkering to build apparatus when they don't have exactly what they need. And when tackling a new research problem, do you ever have precisely what you need?

While you can make do with measuring cups and kitchen scales, I'm with the Chemical Heritage Foundation's Erin McLeary, who notes the appeal of having the real stuff in your hands.  These days you can easily and inexpensively acquire a few real beakers, graduated cylinders and other lab equipment -- along with gloves and other protective gear.

So if you're looking for an interesting and unique gift for a kid interested in science, try assembling a small kit and including the instructions and materials for a couple of experiments.  For starters, extracting DNA from dried peas or copper electroplating (yes, it uses something you shouldn't eat - don't and wash your hands) or even the infamous water electrolysis (sans smoldering splint and thereby less risk of singed eyebrows).  Offer to help supervise or be the videographer.

To read more of what I've written about chemistry kits and doing chemistry outside the laboratory see:

"Homemade Chemists" in Nature Chemistry
"Felony Science" at Slate
"Handheld Chemistry" on the blog, about the making of ammonia in your hand

Polysemy and Polyphony: Listening to Messiah

Last spring I wrote a piece for Nature Chemistry on polysemy — the phenomenon where words take on quite different meanings in different contexts. The iconic chemistry example might be mole (the quantity versus the animal versus the verb1), but there's a long list.

So you might think that when I ran into a homograph2 on Twitter the other day, I'd be alert to the possibility. My first thought when the conversation between two chemists about the insights they find in Messiah showed up in my feed they were talking about the classic quantum mechanics text by French physicist Albert Messiah.  Actually, not.  Handel's Messiah was the text under discussion.  Polyphony crashes into polysemy.  And evidence I really am a science geek first and foremost.

The text is still in print, though Albert Messiah died in 2013 at aged 92.   I used Messiah's text when I took a year long course in quantum physics as a graduate student (from the physics department, have exhausted the chemistry offerings as an undergrad). We pronounced his name "mess-ee-uh" rather than "mess-eye-uh," making this technically a homograph (though not a capitonym3).  I wondered today how he might have pronounced his name, is it really a homograph, or did my professor simply choose to pronounce it this way to avoid sounding like an evangelical preacher when he assigned reading?  I dove into the interwebs to see if I could uncover any clues.  I discovered Messiah had been part of the French Resistance in World War II (joining at age 19, the age my youngest son is now), worked at the Institute for Advanced Study in Princeton with Niels Bohr and eventually returned to France to teach and write this text.

I also listened to a few minutes of a presentation Messiah gave in 2009 at Le Ecole Polytechnique.  It was oddly moving to hear the voice of someone whose written words I had spent so much time wrestling with almost forty years ago.  And at the end of the questions, I learned how he pronounced his name.

And, on the Sceptical Chymist, Reuben Hudson has a post responding to my column on a different kind of doubling-up in chemical language.

1.  Yes, mole is a verb, to mole a garden is to remove the moles.
2.  Homographs are words that have the same spelling, but different pronunciation (lead and lead).
3.  Capitonyms are homographs with different capitalization.  DEFT and deft.

Shedding some light on chemistry: Mole Day and the Year of Light

[If you want to participate in some science about science blogs, see the bottom of this post!]

It's October and there is lots of science to celebrate.  Chemists in the US and elsewhere are celebrating Mole Day on Friday (October 23 at 6:02 pm) to honor Avogadro's number (6.02 x 1023 items are in a mole -- it's the chemist's version of a dozen).  It's also the International Year of Light, and while you might think that light is the purview of physicists, it's an element of chemistry as well.  I suggested in a recent essay that one might want to celebrate the year of light on the 10th October at 3 in the afternoon (3 x 1010  is the speed of light in cm/sec)

I've written two pieces on the relationship between chemistry and light for the celebration.  The first for Nature Chemistry, The Enlightenment of Chemistry, looks at the two-way relationship between chemistry and light.  Light is  not just an energy source for doing chemistry, but the production of light in various ways has pushed chemistry forward.  The full text is here.

The second, for the UN's Year of Light blog celebrates the October 27th anniversary of Bunsen's and Kirchhoff's publication on the spectroscope and atomic emission spectra — and the role the spectroscope played in not only filling out the periodic table, but in confirming the periodicity of the table.
"Hunting for new elements spectroscopically meant you didn’t actually need to have any of it in your lab or even on your planet, as long as you could observe the light from a burning sample. In 1868 several chemists and astronomers independently observed a faint line in the spectrum of the sun, and assigned it to a new element, helium, which as far as they knew did not exist on earth. It would take nearly 30 years for two Swedish chemists to confirm that it was present on earth — by matching the spectrum with that of a gas found in a uranium ore. (The helium to be found on earth comes from radioactive decay.)" — read the rest here.
Want to participate in some science to celebrate?

Help us do science! I’ve teamed up with researcher Paige Brown Jarreau to create a survey of the Culture of Chemistry's readers. By participating, you’ll be helping me improve the blog and contributing to SCIENCE on blog readership. You will also get science art from Paige's Photography for participating, as well as a chance to win a t-shirt, a $50 Amazon gift card and other perks!   It should only take 10-15 minutes to complete. You can find the survey here:

Building scientists #istandwithahmed #kierawilmot

So what's this kid doing in the high school auditorium after school?  He's drilled holes and put pipes into a cooler, there's some kind of heating device or trigger. Wires.  And it looks like a boat load of some sort of chemical in that bowl that he's dumping in there.  And then...and it shoots out some kind of gas.  Kids scream. The gas begins to cover the stage.

"What's happening?" wants to know the teacher who hears the commotion from the hallway.  "I'm testing a fog machine I built for the class play."

Yes, at first glance the situation looks potentially perilous.  But a quick question, followed by a bit of common sense and the teacher is reassured that all is well.

Now that everyone is sure that there is no bomb, what should happen to the kid?

A.  Pull the child into the principal's office and demand that he sign a statement admitting his guilt.

B.  Call the police, who will arrest him and charge him with building an explosive device.

C. Call the police, who will arrest him and charge him with building a "hoax bomb"

D. Nominate him for a theater award for special effects, for having designed and built an inexpensive fog machine to use for the school's upcoming production of Grease.

The kid is my kid and the school's response was D.  But imagine if my kid wasn't white and male.  If his name were Ahmed Mohamed or Kiera Wilmot?  There might have been handcuffs, felony charges, letters home to parents about "the incident".  If someone had called the police, would they have arrested him because he couldn't explain why he'd built one, when they could have rented a fog machine?  (The police thought it suspicious when Ahmed Mohamed couldn't tell them anything more than his device was a clock.) Why would you build a fog machine, or a clock?  He must have built it for a purpose, nefarious almost certainly.

Perhaps the purpose was to understand how these machines work?  There is an amazing amount of joy in showing that you understand something well enough to build a working apparatus. To tweak and fix.

As a parent, I want the school to exercise an abundance of caution.  But once you're sure it's just a clock — or a fog machine — perhaps it's time to slow down, and engage some common sense.  Is there anything else that suggests this kid would build anything danger?  Besides his name, or the color of her skin, or his religion.

Scientists and engineers are not hatched full grown from eggs in labs.  As kids, they tinker and think and build and design, with Legos and parts from Radio Shack and Home Depot.  They are in theater and on robotics and Science Olympiad teams.  We need to get as excited about what they do as we are about how the football team is doing.

From the portals of hell to built-in fire protection: intumescents

A friend posted the link to this demonstration, wondering if it was safe. (Do listen to the children in the background - their cries of "kraken" at 1:02 are worth it.  Science is great fun!)

The caption that came with it noted that it was a mixture of ammonium dichromate ((NH4)2Cr2O)and HgSCN (mercurous thiocyanate).1 Mercury and chromium, probably not something you want to eat I told my friend. The whole thing made me curious, just what were those tentacles come out of the burning pile? And what chemical reactions were driving it?

It's a coupled set of decomposition reactions. The volcano comes from the decomposition of ammonium dichromate

(NH4)2Cr2O7(s) → Cr2O3(s)+ N2(g)+ 4H2O(g)

The reaction produces a lot of heat, which makes the particles being thrown off by the rapid expansion of the two gases (nitrogen and water vapor) glow.

The heat then triggers the decomposition of the mercury compound:

2 Hg(SCN)2(s) → 2HgS + 4CS2 + carbon nitrides

The erupting tentacles are an example of intumescence2, a property of mercury thiocyanates noted long ago by the venerable Friedrich Wöhler3. It's a well known demonstration, often called Pharaoh's Serpents. Many material intumesce when heated, and thus produce their own insulation.  Some passive fire protection systems rely on this property of polymers, by which they essentially rapidly produce their own insulating layer upon heating, or by swelling up to block air ducts to prevent smoke and other gases from spreading too quickly through a ventilation system.

It works with mercuric thiocynate as well (Hg(SCN)2) — by some accounts even better — and better yet if you toss a bit of potassium nitrate and a bit of fuel in the form of sugars. In other bits of historical trivia, the mercuric thiocyanate was originally made by the aptly named Otto Hermes. The sale of mercuric Pharaoh's Eggs ceased after some kids ate them with deleterious (fatal) effects.

If you just want to see the snakes minus chromium salts or mercury - try this demonstration based on calcium gluconate instead or check out pyrotechnic expert Tenney Davis suggestions in the Journal of Chemical Education.

1.  From the Latin verb "to swell" — related to thumb and tuber (as in root vegetables like potatoes)

2.  The chemist who showed in 1828 that compounds made by nature do not have some "vital essence" that distinguishes them from the same structure crafted by a chemist from inorganic (never living) materials.  Something the Food Babe and hawkers of 'bioidentical' hormones do not get.

Read more:

Brian Clegg at Chemistry World.  A paper on the demonstration from Journal of Chemical Education in 1940, by Tenney Davis of MIT who taught courses in explosives way back when ($).