Field of Science

Easter fires: Rainbow demonstration rises again

It the the custom in many Christian denominations to light a Pascal fire at their Easter rites. For Catholics, this is done after sunset on Saturday night. The fire is kindled outside the church and in many traditions a large candle and/or many candles are lit from the flames. Lighting the fire is often problematic, it should be visible to the people assembled, but confined to prevent hazards. It can be smoky.  This weekend I became aware of an alternative to the traditional wood fire, replacing it with a rock salt and alcohol mixture.  This sounds like a great idea.  It is smoke free — you could do it inside — and that as these sets of directions suggest, you can add other salts to make beautiful colors in the flames.  It is, in fact, a TERRIBLE idea.

This is just a version of a chemistry demonstration, often called the rainbow demonstration, that is so dangerous it should not be done. Period. The rainbow demonstration has led to many serious burn injuries in onlookers and teachers, the Washington Post has an overview here.  Under certain circumstances it can produce a flame jet. See this notice from the American Chemical Society, and this longer article about the hazards at the Journal of Chemical Education.

The dangers is that vapors from the alcohol can travel out of the container or the salt/alcohol mixture and along the ground, then ignite in a ribbon of flame. I note that the National Altar Guild
link with instructions recognizes the vapors might escape, but doesn't seem to realize the hazard this presents.

Some years back the American Chemical Society urged chemists to contact their local high school chemistry teachers about the rainbow demonstration to be sure the warnings reached them. It might be time to encourage chemists to reach out to their local churches to be sure they are aware as well. 

The weight of water

While writing a piece for Nature Chemistry about the hidden depths of the periodic table (the more than 3000 isotopes that could be stacked onto their elemental spots), I wandered across an interesting set of papers on heavy water and isotopic tracing, which led to another piece for Nature Chemistry (The weight of water). In one of the papers, future Nobelist George de Hevesy deuterates goldfish by crowding some twenty (albeit tiny) goldfish into 60 ml of water, in another he reports making thousands of distillations of urine to recapture the water, measure its density and track deuterium through the human body.

Heavy water (D2O) is water where the hydrogens have been replaced with deuterium, an isotope of hydrogen that weighs about twice as much as standard hydrogen. Heavy water weighs just over 10% more than regular water, a tablespoon weighs only about a gram more, so it is probably not noticeable should you heft a glass of it.

And that's the question — should you heft a glass of it? In small amounts it is certainly safe to drink, and as I recently learned, used in human metabolic studies in doses of about 10 ml. An interesting question raised in the papers I read was about the taste of heavy water. One report suggests a burning sensation might be felt when drinking it, another (by Harold Urey, who discovered deuterium) suggests it tastes like undeuterated water. But other reports say it tastes sweet.

With a bit of help from my youngest son, I set up a repeat of Urey's blind taste test. And was surprised to find I could indeed taste the difference. It is sweet.

And for the next few weeks, until the last of the extra deuterium clears my systems, I'll be just a little bit heavier than usual.

Elements of revenge

I seriously can’t write fiction. I suspect it's not lack of imagination, but some odd form of writer’s block. Or perhaps it is too many years devoted to sifting defensible reality from experimental and computational data. Or is it that I’m unwilling to ask a reader to be confused about the real, the possibly real and the entirely imagined? Or maybe it is because the one and only piece of published fiction I wrote, came (almost) true within the year?  Would any other fiction I wrote become real? That’s clearly a flight of fancy, but even with one data point, do I want to take the risk?

I was invited to write a commentary on the elements that scientists thought they'd discovered (but hadn't) for Nature Chemistry's issue celebrating the International Year of the Periodic Table.  The IUPAC guideline for element names says that you can't re-use names already in circulation in the literature, even if they were ultimately discarded. Which got me thinking if that could be a way for an unscrupulous scientist to crush the dreams of a competitor of having an element named for them. Despite my demonstrated inability to write good fiction, I drafted an introduction to the essay that played out this idea.

In the end, I wrote a non-fictional introduction to the essay (which you can read here if you are of the mind to do so). But if I were to write a piece of fiction about the elements, it might begin like this:

Prof. Exuvgen leaned back in her desk chair and wondered for the thousandth time why she’d ever signed that retirement agreement. Time was slipping through her fingers.  In a month, she’d have to hand over the key codes and walk out the door.  No access to her data and worse yet, no access to the tools she would need to analyze it, that idiot of a director had made it clear her account would be wiped — wiped — at midnight on the 30th, and anything left in her office trucked out to the dumpster.  Tang Woh Kow, they maintained, was right. There were 243 elements in the universe and no more. When Tam Besper saw the traces of zuzenium in 2069, right in this building, that was the end of the era of the element hunters. The last chance to have your name remembered in every chemistry book in the solar system, if not the galaxy. Though if the Vulcans had their way, everyone would be using the systematic names.

Running her hands through her short grey hair, she turned again to the data on the screen.  She’d spent thirty years working toward puncturing Kow's ceiling on the elements, the last ten racing Sabaxoar’s extravagantly funded group on the moon. What was it Maxine had said at that last meeting? Oh, right. Time. That she wasn't in a hurry, she had years to work on this, given lunar life expectancies. And with that Maxine shook her blonde curls and floated off.  Would the director take her more seriously if she looked less weary, grey and face it, old?

Time. It's running out, was there enough to say, now, without a doubt, that they’d turned up an atom or two of 244 Sym in that last run? Maybe, though maybe that oxide of muscovium was rearing its ugly head, this wouldn't be the first umbral element sunk by 115. Certainly there was strong evidence of a new isotope of 243.  Time, there just wasn't enough time.

She tapped the bud in her ear, and started composing the manuscript of one last paper.  “We present here evidence for the creation of the 616 isotope of 243 Zz, half-life 82 msecs, along with traces of element 244, Uuq.” She glanced up at the list of proposed names for 244 her group had kept on the whiteboard, derived from the names of birthplaces and long dead mentors and far-flung galaxies and grinned wickedly. “…for which we propose the name sabaxorium, symbol Sx, in honor of our respected and long time competitor in this hunt, Maxine Sabaxoar.”

Four months later, Maxine wakes up to a tweetstorm of congratulations for having the first trans-zuzenium element named for her. She pulls up the paper and seeing the unmistakable traces of MvO in the accompanying supplementary data dump, shrieks, "I've been robbed.”
In the 1970s, Tang Wah Kow of New Method College in Hong Kong suggested (based on an odd theory about triads and octaves) that the upper level for an element was Z=243. Further, he proposed that when that element was ultimately discovered, it should be called zuzenium (Zz). The suggested name he said was, "...deduced from a Chinese idiom 'The name stands behind Zun Zen, who (Zun Zen) came last on the list of successful candidates in a royal examination." [In "An Octagonal Prismatic Periodic Table" J. Chem. Ed. 49, 59 (1972)]

Five Books: A short reading list for chemistry

Only five books? And the five best books? Last month I did an interview via email with Caspar Henderson (who wrote a marvelous bestiary for the new century: The Book of Barely Imagined Beings) on the best five books I would put on a reading list titled "Chemistry."  It's now up on the site — Five Books.  But the hardest part was not answering the great questions Caspar posed, but figuring out what five books to list. What did I want this list to do? Teach you chemistry? Maybe. Or give you a sense of what I find fascinating and beautiful and compelling about chemistry? Definitely!

I thought about various friends, curious and readers, but who don't have much background in the sciences and math.  What would I pull from my shelves for them to read?  Something that teaches you to decode a bit of the chemistry, a biography - what is the life of a scientist really like.  Something that is compelling, that drags you into a story you can't put down. Something that shows off the beauty of the world at the atomic and molecular level.

Something that teaches you to decode a bit of the chemistry:
Why does asparagus make my wee smell? And 57 other curious food and drink questions by Andy Brunning of Compound Interest. A bold graphical look at the chemistry of what we eat, with lots of quick explanations of weird (but useful) words of science like chromatography. 
What is the life of a scientist really like:
Obsessive Genius: The Inner World of Marie Curie by Barbara Goldsmith.  Of course there had to be Marie Curie. And this unsparing biography of her pulls the curtain away on what it can mean to plunge into research with all your being.
Compelling stories with chemistry at their heart:
The Poisoner's Handbook: Murder and the Birth of Forensic Medicine in Jazz Age New York by Deborah Blum. Some molecules are thugs, some turn witness for the prosecution. Real crimes, real molecules.  (And her new book on the rise of food safety, The Poison Squad, which is in the stack on my desk, is just as good.) 
The beauty of the atomic and molecular world:
H2O: A biography of water by Phillip Ball Chemistry laid out for the layperson with care and delight. Clouds are not what you think!
The Disappearing Spoon: And Other True Tales of Madness, Love, and the History of the World from the Periodic Table of the Elements by Sam Kean. There's a dark side to the periodic table.
Read the whole essay to find out more about what is fascinating about chemistry (at least to me), what I do as a chemist, and of course, about these five books. Want more book recommendations about chemistry? Want to know what the runners up were? Leave me a note in the comments!

Chemistry not your thing? Go read Caspar's bestiary about the wildly improbable creatures that inhabit the very real world, from sea butterflies to yetis (or at least yeti crabs), it's a wide ranging exploration of the corners of the biological world. To quote a reviewer: "There is something lovely about a book that takes on so many disciplines and tackles them with confidence." There is indeed.

[Cross posted from Quantum Theology]

Trying to explain earthing with atoms

My ungrounded feet in rubber boots.
This week the Washington Post has an article headlined "Could walking barefoot on grass improve your health? Some science suggests it can."  The link itself is subtitled: The science behind grounding.

The article gets a lot of things right about atoms (they make up everthing!), but it confuses "free-radicals" with positive ions. (Free radicals don't have to be charged.) Then it tries to explain why negative ions can help. And while it is true that a positive ion and a negative ion can react in some circumstance to produce a neutral compound (think of hydroxide and hydrogen ions reacting to make water in an acid base reaction), random negative ions won't necessarily disarm a free radical.  You need an antioxidant for that, a molecule that can participate in a reaction that can soak up extra electrons.  You still need to eat your vegetable and wear sunscreen.

Negative ions and positive ions co-exist quite nicely in your body. You need those positively charged potassium ions, in fact, to keep your heart beating rhythmically. So on its face, the "science behind grounding" given in the article is bunk. If all those negative ions in the ground started neutralizing all the positive ions in our bodies, we'd be dead.

While I get this is a not a science news piece, but a perspective piece (a "[d]iscussion of news topics with a point of view, including narratives by individuals regarding their own experiences"), I wish someone at the Post had fact-checked the science.  Yes, it feels nice to walk barefoot on the grass, or to be outside.  I'm pretty certain the negative ions aren't the reason why.

Hunting up the ghosts of elements

This post originally appeared at the UNESCO International Year of Light's blog, in October 2015.  The site is no longer available.

Interior of an antique spectroscope.
If you’ve seen the flash of yellow-orange flames when a pot boils over on a gas stove, you’ve gotten a glimpse of the ghost of an atom.  The color is part of the atom’s spectrum.

In the late 17th century, Isaac Newton used the Latin word for ghost, spectrum, to describe the bands of colors he saw when light shone through a prism. One hundred and fifty years later, Joseph von Fraunhofer noticed he could see bright lines instead of the bands of colors when looking at certain flames through a prism.  He went on to develop an instrument to measure these spectral lines, called a spectroscope, and used it to catalog the lines seen in the sun’s light and in the light from other stars.

It would take almost another fifty years to figure out that Fraunhofer’s lines were the ghosts of chemical elements, when Gustav Kirchhoff and Robert Bunsen (the inventor of the ubiquitous Bunsen burner) teamed up to create a spectroscope that used Bunsen’s new hotter, gas burner to ignite the samples.  They noted that that each element produced a characteristic set of lines when burned, a spectral fingerprint, that could be used to identify it.

In October of 1860, Kirchhoff and Bunsen announced they had used their spectroscope to discover a new chemical element, which they named cesium, for the blue color of its principal line. Chemists quickly began to use Bunsen’s spectroscope to find new elements.  A few months later Kirchhoff and Bunsen found two bright ruby red lines in an extract of a silicate mineral lepidolite, the spectral traces of another new element, rubidium.

Thallium’s ghostly green emanations were first observed by William Crookes, indium, ironically named for its violet lines by its color blind discoverer Ferdinand Reich.  Paul-Émile Lecoq de Boisbaudran spectroscopically identified element 66 in a sample painstakingly extracted from his marble hearth, and instead of naming it for the colors of the lines, called it dysprosium, from the Greek for “hard to get” — because it was.

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.)

Spectroscopy certainly helped chemists fill out the periodic table, adding more than a dozen new elements to the collection.  But it also played a significant role in confirming predictive power of periodicity. When Dmitri Mendeleev proposed his version of the periodic table, he left blanks for yet-to-be-discovered elements, underneath elements which should have similar properties.  In 1875, Lecoq, the same man who had so patiently extracted dysprosium from his fireplace, sifted through 4 metric tons of  zincblende to show that it contained traces of a new element which fit neatly into the space Mendeleev had reserved for it underneath aluminum.  Lecoq named the element gallium, in honor of his home, France, and perhaps playing off his own name, as the Latin for le coq, the rooster, is gallus.  It was a powerful demonstration of Mendeleev’s theory.

These ghostly lines produced by elements helped fuel yet another critical discovery that would have far reaching consequences for chemists’ understanding of the periodic table:  quantum mechanics.  Niels Bohr’s quantum mechanical model of the atom opened the door to explaining chemical elements line spectra. Though more accurate and sophisticated quantum mechanical models of the atom now exist, Bohr’s model showed the relationship between the lines and an atom’s electron by insisting that the electrons’ energies were quantized, that is, they could only have certain energies.

So why do atoms have ghosts?  When an atom is heated to high temperatures, as in a flame, the energy it absorbs excites its electrons.  You can think of the electrons in an atom as being on an energy ladder.  They can only have energies that match the rungs of the ladder, and each type of atom has a unique arrangement of the rungs.  When the atom absorbs energy, its electrons move to higher rungs.  Excited electrons are unstable. They quickly return to their original arrangement, giving off some their excess energy in the form of light as they do.  The color, the wavelength) of the light emitted depends on the difference in energy between the rungs.  The colors of light emitted are the ghosts of the energy rungs.  Since each element has a unique pattern of rungs, it will have a unique spectrum of emitted light and so revealing their presence to the sharp eyes of spectroscopists.

Chemists still use the light emitted and absorbed by atoms and molecules to identify their presence.  We hunt for the structure of the universe in its ghosts.

More Information

If you want a way to see the ghosts of atoms, try this DIY folding spectroscope you can attach to your phone. Use it to check out the light from a neon sign or from a street light!

For a wonderful description of the elements, including stories of how they were first discovered, read John Emsley’s Nature’s Building Blocks.


Sikhote-Alin meteorite from Vatican Observatory's
On July 13th, the Earth Science Women’s Network is hosting Science-A-Thon, in which participating scientists are chronicling a day in their life on Twitter and Instagram (follow #dayofscience and #scienceathon).

Join me for the day!  I'll be posting a photo every hour on a day when I'll be working from the Vatican Observatory in Albano Laziale, outside of Rome.  Starting with my early morning stop at the espresso bar through a full day of science behind the walls of Vatican City.   There might even be aliens from other worlds (of the inorganic variety). The observatory might seem focused on anything-but-earth science, but the meteorites that the earth sweeps up as she moves through the heavens are clues not only to the otherworldly, but to our own planet's history.

Participants are listed by country — so far I'm the only one under "Vatican City"!

This is a first-ever fund raiser for the Earth Science Women’s Network, so if you are inclined to support them, you can donate here.

Hidden figures: 2.303, slide rules and classrooms mired in the last century

A five -place table of logarithms from my dad's CRC Handbook of 
Mathematics (why is that set of values circled?) and a circa 
1958 Hemmi 257 slide rule designed for chemical calculations.  

 Wonder why random values of 2.303 are "hidden" in formulae? To make them easier to use with a slide rule.

A slide rule?  The last slide rule slid out the door of Keuffel & Esser in 1975 (they sent their engraving equipment to the Smithsonian).  You can still find them, used and even new - still packaged up to sell to engineers and scientists.  The Oughtred Society has a online museum, as well.

We still have my mother-in-law's K&E, in it's leather case with her name impressed into it.  Family history says she bought it with the money she earned tutoring Jackie Robinson in chemistry at UCLA.

I have an essay out in this month's Nature Chemistry, "It figures", about how the computational tools we use shapes what we teach and not necessarily in good ways. Given that slide rules were obsolete by the time many of my student's parents were born, why does their use still linger in general chemistry book?  (The 2.303's in texts are lowly going away. I checked texts running back about a decade.)

More critically to my mind why, several decades after  digital computing tools became ubiquitous on college campuses do many physical chemistry texts eschew any discussion of numerical techniques for solving the rate equations for a chemical reaction?  I suspect the chasm between the computational tools used in the field and those used in the classroom is a result of apathy. We teach what we learned as we learned it.  As I note in the article, I don't think it is defensible on intellectual grounds.

Don't know how to use a slide rule?  It's fun, it's geeky. No need to buy one to play, check out this simulator and the instructions at Nature Chemistry!

You can read the article here:

1.  2.303 is the natural log of 10. To change the base of logs recognize that
x = blogbx
ln(x) = ln(10log10x)
ln(x) = log10x ln(10)
ln(x) =(log10x)(2.303)
ln(x) = 2.303(log10x)

Implications of Charles law in a biological matrix: farts

See note 3 for source.
Maggie Koerth-Baker has a great piece up at the 538 blog: "How Big Is A Fart? Somewhere Between A Bottle Of Nail Polish And A Can Of Soda."  It's well researched, digging into the biomedical literature with verve.  And it's great that she gives the answer a context, it's easier to visualize a bottle of nail polish than a 17 ml blob for most people, me included.

I'm not at all surprised at what you can find in the primary literature (I tracked down papers on exploding people and deuterated dogs1 for my introductory chemistry class last spring). The piece is the first in a series Science Question From A Toddler, though I suspect that people somewhat past the target age group (5 and under) would be interested in the answer to this question, too.

In a footnote Koerth-Baker suggests that farts in the body would be smaller because the gas would be compressed inside the body.  But the pressure inside the human colon is the same as atmospheric pressure.  Farts and burps keep it that way. What's different is the temperature, higher inside the body by about 30oF (17oC).  Gases expand at higher temperatures. You can use Charles' law to figure out by how much the volume changes with changes in temperature:  V2=(T2/T1)V2

The researchers measured the volume of the farts at room temperature (I read the paper!), so the volume of a fart should be slightly larger in the body than the reported numbers by a factor of (310/293) or about 6% larger.  So how big is a fart?  Just before exit, it's about the size of a 14 ounce ketchup bottle for the largest one in the 1997 study.

The details of the experiments are fascinating.  The technique for quantitatively2 capturing flatus in the bathtub is elegant, and while a significant improvement over the method used for the studies in the 1860s3 you have to wonder how they got volunteers for either experiment.  And speaking of volunteers, the assessment of the "flatus perception threshold" was done by delivering 100 ml of an odorant mixture "from a large 250ml syringe in about 1s, 1 meter beneath the nose of the panel members, mimicking a flatus emission."

And just in case you don't think this is serious stuff: "The common tendency to treat rectal gas as a humorous topic has obscured appreciation of the complex physiology that underlies the formation of this gas." Suarez et al. American Journal of Physiology  272, G1028-G1033 (1997).

1.  The physiological effects of drinking heavy water, D2O, on dogs.  If you've ever wondered what would happen if your poured that little vial of D2O into your coffee, the answer is not much.  It's not great for the dogs as a steady diet, but a sip or two won't hurt.
2.  The fancy chemistry term for "we got all of it!"
3.  See the figure, from Tangerman, "Measurement and biological significance of the volatile sulfur compounds hydrogen sulfide, methanethiol and dimethyl sulfide in various biological matrices" Journal of Chromatography B, 877,  3366-3377 (2009).

Chemists: Strangers to fiction

That Mars habitat?
"The basement corridor is dim, I can hear pumps chugging, hoods noisily venting, and the solid-state physicist down the hall swearing. 'Welcome to Mars!' says the cheery sign outside my colleague’s door. Perhaps it is the pile of grading on my desk or the endless round of meetings on my calendar that is fuelling my escapist fantasy, but every time I pass Selby’s office, I imagine the door is a portal and if I were to walk through, I’d  find myself in a habitat on Mars, its pumps working hard to compress the thin atmosphere." from "Strangers to Fiction" in Nature Chemistry8, 636-637 (2016).

I've been a sci-fi fan for going on five decades, imagining myself in labs on Mars, mining comets, and exploring strange new worlds. I don't read it for the chemistry, which is a good thing, because there isn't much fiction in which chemistry plays a key role.

My latest Nature Chemistry Thesis column looks at chemistry and fiction, suggesting that there are good reasons to both read SF, particularly for young chemists, and for chemists to encourage the writing of chemistry-inflected science fiction.  And if you have the talent for it (which I do not!) perhaps even give the writing of it a fly.

You can read the whole thing here.  My list of fictional chemistry is here.