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 30^oF (17^oC).  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.

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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 Chemistry, 8, 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.

A matter of degrees: when low temperatures were hot

Diagram of a thermometer similar to

the one describe by Leurechon, c. 1638.

Note that  hotter temperatures have 

smaller magnitudes degrees associated with 

them. Image from Wellcome collection, 

used under CC license.

We say the mercury is rising to mean it's getting hot out, despite the fact that most home thermometers have no mercury in them anymore.  Regardless of the liquid they contain, the level rises with increasing temperature in the iconic liquid thermometer.  But this was not always the case.

The word thermometer was first coined (in French) in a book of mathematical recreations written in 1626 by Jean Leurechon, SJ (writing as Hendrik van Etten).  In his description he notes the thermometer you can construct from a glass tube and small container of water (or other non-viscous liquid) can be used to quantify temperature by placing marks on the glass, associating each with some fraction of the classical four (or eight) degrees of hotness.  Such thermometers, he suggests, can be used to adjust the temperature of a room or a furnace, to record (and predict) the weather and to measure fevers in the ill.

But Leurechon's thermometer (and similar designs) were constructed such that as the temperature increased, the water level in the tube fell.  Increases in temperature caused the air trapped in the ball at the top of the tube to increase in volume, pushing the liquid down in the tube.  (These are air thermometers, in contrast to the familiar liquid thermometers in widespread use today.) A reading of 9 degrees on the thermometer shown in the sketch accompanying Leurechon's thermometer problem was colder than that of 2 degrees (see also the one in Robert Fludd's diagram, in the figure.)

A century later, Anders Celsius constructed a temperature scale based on water's phase changes which ran in the same direction.  Water on Celsius' scale boiled at 0 degrees and froze at 100 degrees. This reverse run didn't last long, two years later Carl Linnaeus (of taxonomic fame) used the scale to describe conditions in a greenhouse, but flipped it to the form in which we know it today, where 100 is the boiling point of water.

It is tempting to think that Celsius' scale ran in the direction it did because it mimicked the earliest marked thermometers. But Fahrenheit's scale, which preceded Celsius' by two decades, runs in the modern direction, things get hotter in the positive direction. This also parallels the classic notions of degrees of heat in play during the medieval period. There were four (or eight or six, depending on the source) degrees of heat, the first being more or less physiological temperature, the fourth being a blazing hot furnace.

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The word degree has its roots in the Latin degradum, a down step.  This matches Leurechon and Celsius' use - 9 degrees is eight steps lower (colder) than 1 degree.

Chemical fiction

Topi Barr's Antithiotimoline is in this vintage Analog

Seven years ago, Andy Mitchinson, an editor at Nature, wrote at The Sceptical Chymist (Episodes II and III) about the dearth of science fiction that involved the science of chemistry in a substantive way.  Why isn't there more of it?

He pointed to a list put together by Connie Willis, an award winning SF author, and an article by Philip Ball in Chemistry World.

I'm working on a column for Nature Chemistry about the ways in which chemistry and science fiction play off each other.  Is science fiction more than escapist entertainment?  Should chemists care that there's not more chemistry inflected fiction out there?  Should we deliberately expose students to science fiction? Should we encourage them to write it?

To go alone with the piece, I'm trying to create a periodic table of chemical fiction (not including articles called out by Retraction Watch).  Are there pieces on my list you particularly love?  Something I'm missing?  I'd love to hear in the comments!

For a full set of periodic science fiction short stories, I encourage you to browse Michael Swanwick's Periodic Table of Science Fiction.  What really happened to the Hindenburg?

	Author	Work
As	Asimov, Isaac	Whiff of Death, The Endochronic Properties of Resublimated Thiotimoline, Thiotimoline to the Stars, Pate de Fois Gras
Pb	Ball, Philip	The Sun and Moon Corrupted
Ba	Barr, Topi	“Antithiotimoline”
B	Bujold, Lois McMaster	Vorkosigan series
Ac	Christie, Agatha	"The Blue Geranium” in The Thirteen Problems
Cl	Clements, Hal	Phases in Chaos
Co	Conan Doyle, Arthur	Holmes
Md	Dewar, Michael	“Temporal Chirality:  The Burgenstock Communication”
F	Foster Wallace, David	Infinite Jest
Ag	Goodman, Allegra	Intuition
He	Heinlein, Robert	Glory Road, Have Spacesuit will Travel
Hf	Hoffman, Roald	Oxygen
Li	King, Laurie	Russell & Holmes series
U	Le Guin, Ursula	“Schrödinger’s Cat”
Sn	Lem, Stanislaw	“Uranium Earpieces” in Mortal Engines
P	Levi, Primo	The Monkey’s Wrench
Am	McCaffrey, Anne	Pern series
H	Piper, H Beam	Omnilingual
Kr	Robinson, Kim Stanley	Mars series
O	Sachs, Oliver	Uncle Tungsten
Dy	Sayer, Dorothy	The Documents in the Case
Sm	Smith, Edward Elmer “Doc”	“Tedric,” “Lord Tedric" in The Best of E. E. “Doc” Smith
Ne	Stephenson, Neal	Anathem
Br	Stoker, Bram	Dracula
Fr	Vance, Jack	“Potters of Firsk”
K	Vonnegut, Kurt	Cat’s Cradle
V	Vourvoulias, Sabrina	INK
Hg	Well, H.G.	“The Diamond Maker” in The Stolen Bacillus and Other Incidents
C	Willis, Connie	The Sidon in the Mirror

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.

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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.

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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.