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.

Formaldehyde: not just for dead things

Next spring I'm teaching a course on the physical chemistry of food while a colleague is teaching a course on the analytical chemistry of foodstuffs.  Among other science texts we'll be using John Coupland's Introduction to the Physical Chemistry of Food, but I'm also collecting short pieces to put some of the work into a historical and social context.

These aren't actual biological specimens preserved
in formaldehyde, but Halloween decorations.  

Though these days we tend to think of chemists as the untrustworthy creators of toxic, artificial everything, the systematic training of chemists was driven in part by the desire for the public to know what was in their food and water.  In 19th century Britain, hundreds of chemists made their living testing the purity of everything from butter to well water.  So when the Food Babe tells you there is something "yucky" in your food, the reason we know it is there is some chemist developed a careful protocol for its analysis, and other chemists tested the material.

Molecular structure
of formaldehyde

I've been thinking about formaldehyde, one of the simplest organic molecules (to a chemist, organic means made up mostly of carbon and hydrogen atoms, and has nothing to do with whether the molecule is synthetic or natural or...). Last year, formaldehyde, which is a preservative, was in the news because Johnson & Johnson had agreed to remove it from baby shampoo, though as Matt Hartings and Tara Haelle clearly pointed out in a piece at Slate, it was in such low concentrations that it posed no risk to babies (who, they point out, themselves contain substantial amounts of formaldehyde.)

Pepsi is reformulating Diet Pepsi to take out the artificial sweetener aspartame. The Food Babe is crowing that she and her army have forced Kraft to remove the so-called coal tar dyes (e.g. tartrazine/FD&C Yellow 5), to be replaced by natural colorings from spices.  What does all this have do do with formaldehyde?

From the Food Babe's 'campaign' literature.

To start with those natural colorings - at least one of them used in the UK version of mac and cheese, beta-carotene, isn't extracted from natural sources but synthesized from petroleum feedstocks (just like those coal-tar dyes).  One of the starting materials:  formaldehyde. The other natural colorings on the table — annatto, turmeric and paprika — are not quite what you might think either.  While you might imagine shaking in some spices from a quaint bottle, the spices themselves are not used as colorants, the colorants are extracted using organic (not that kind of organic, the chemist's kind of organic) solvents, such as ethyl acetate.  It's unclear to me why these colorants, particularly beta-carotene pass muster with the Food Babe.


Aspartame is sometimes vilified because it is metabolized into methanol and formaldehyde in the body.  Which it is.  You already contain a lot of formaldehyde, about 12 milligrams per liter of fluid in your cells.  One source is metabolism of the amino acids, particularly, serine and glycine (in naturally occurring proteins), from which your body scavenges methyl groups (CH₃) to pop on to various structures.  Aspartame is a very tiny protein, so the same pathways that produce methanol and formaldehyde from natural sources, dismantle aspartame to yield methanol and formaldehyde, though the amounts produced are tens of times lower than what comes from eating apples and fish.

Because formaldehyde occurs naturally in foods (about 5 mg per serving in some fruits, fish is also high, pectin containing fruits such as apples add significantly to the amount of formaldehyde ingested), our bodies have a mechanism for dealing with it, we process about 60 to 100 grams of formaldehyde a day and do so quickly.  Formaldehyde has a half-life of about 1 to 2 minutes in the body.

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Why are those spices colored?  What does it have to do with quantum mechanics, flamingos and canaries?  Read this post, the very first one written for the blog,  to find out.

References
EFSA report on endogenous versus exogenous sources of formaldehyde.
EFSA review of curcurmin, a component of turmeric, which had been suspected of being genotoxic.

Chemophobia: The Boy with a Thorn in His Joints

I'm at ScienceOnline2013 where Carmen Drahl and Dr. Rubidium just finished running a terrific session on chemophobia: how can we bridge the gap between "better living through chemistry" and ads for "chemical-free sleep aids." The thrust of the session was not how to convince people chemistry and chemicals are good, but more about how to inject nuance into the public conversation. Chemicals have risks and benefits — and of course, are unavoidable. But we current view chemical as synonymous with toxic, hazardous, unnatural or just plain bad.

What are the roots of this cultural shift? Can understanding these help scientists and writers communicate more clearly and in the end help people not only understand what is in their "stuff" — chemicals, it's all chemicals — but give them tools to work with and make decisions about the materials that make up the world — chemicals. As @docfreeride (ethicist Janet Stemmwedel) noted at another session yesterday, we can agree on facts, and still make different decisions based on them.

Today's New York Times has a perfect example of the various ways chemophobia presents in the Magazine: The Boy with a Thorn in His Joints. The piece chronicles Susannah Meadow's search for an effective treatment for her son's rheumatoid arthritis. She agonizes about the decision to give him methotrexate (which in high doses is used in anticancer treatment) and turns to alternative treatments, in particular four-marvels powder. There are intense arguments with the pediatricians and with her husband over the issue. I was struck by two things in this piece. First, the language Meadows uses to limn the controversy, and second her ignorance, not so much of the chemistry that is in your face (methotrexate), but of the ways in which chemistry is couched in alternative cultural schemes(four-marvels powder).

It makes me wonder how chemophobia is linked to the language we use to talk about it. It can be nearly impossible for an non-chemist to figure out what methotrexate is (beyond "a chemical"). The very name sounds harsh. Four-marvels powder is easy to parse: a powder with four effects. Its name rings with hope.

I also wonder if we worry more about stuff we are familiar with, we've heard more talk on the street about their risks. So we obsess about vaccines, because we hear and read about the side-effects of vaccines, but how many people know anyone who has died of measles? (One of my sister's friends died of measles when I was a child, before there was a vaccine.) So we get in the Times' piece "I was desperate to find a way...without the drugs." pushed up against "[My husband] has always been more comfortable with pharmaceuticals, more trusting in general."

Of course, four-marvel powder is a pharmaceutical, it's just from a different pharmacopoeia — the traditional Chinese — than the one Meadows or her husband is familiar with. Meadows can read the package insert with information on the side-effects of methotrexate, she may be unaware of the routine advice given in Chinese medicine programs (and yes, there are formal academic programs in Chinese medicine, e.g. at Nanyang Technical University) about four-marvels powder (it should never be given to pregnant women, for example, which might make you hesitate before giving it long term to infants or young children).

The session at SciOnline2013 brainstormed about effective ways to help people develop a better sense of nuance around what is a chemical and what are the risks of this particular chemical? What strategies do you think would be most effective?

Will bromine turn squirrels purple?

Most winters Punxatawney Phil is the furry face of Pennsylvania, but last year, he had competition: meet the purple squirrel of Jersey Shore (which should not be confused with either a television show or a town in New Jersey).

The news report offers a number of theories about the squirrel's unique coloration.  A dye job seems the likely culprit, whether from the squirrel's nesting material or an inadvertent bath in a violet solution.  Computer scientist Krish Pillai had a novel suggestion: "This is not good at all. That color looks very much like Tyrian purple. It is a natural organobromide compound seen in molluscs and rarely found in land animals. The squirrel (possibly) has too much bromide in its system."

Leaving aside that Tyrian purple (produced by a particular class of marine snail and to the best of my knowledge and research abilities by no mammal) is a much redder color, this assertion is roughly equivalent to saying that if I eat too much chloride, say from table salt, my body could start synthesizing Splenda, an organochloride.  No, just, no.

Pillai is apparently extrapolating from reports that bromide (bromine anion - Br^-) has been found contaminating wells near fracking sites.  Calcium bromide is used in drilling fluids to increase density, by some estimates 20% of the bromine used in the US ends up in "clear brine fluids" — mixtures of various bromides.  But it is a long way from bromine ions to 6,6′-dibromoindigo along very specific biochemical pathways.  Which squirrels don't have.  Or humans.  (What can and does happen is that the bromide reacts with various chlorine compounds used in water purification to form organohalides, which aren't healthy to ingest....)

It's worth noting that direct ingestion of dyes can have interesting effects on pigmentation.  Flamingos get their characteristic color from ingesting shrimp pigment, and you can change the color of a canary's feathers by feeding it paprika.  Humans who eat too many carrots can develop carotenemia — they turn orange.  These processes are reversible, stop eating the shrimp or carrots and feather or skin return to their normal coloration.  Unfortunately consuming silver or gold can produce a permanent change in skin coloration, as in argyria.

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An alternate definition of a purple squirrel via Urban Dictionary.

Don't drink the water

"Don't drink the water from the sink!” read a sign taped to the mirror. As I was in rather desperate need of a glass of water before rehearsing the piece I would sing solo at Christmas, I was glad to find someone had left a gallon jug of distilled water and a stack of paper cups. Rehearsing the next day, as I went to grab a cup of water, a colleague pointed out that yesterday someone had mistakenly put out distilled water, which he had swapped for spring water. “Hopefully no one drank it!” he said.

“Why not?” I inquired.

“You’re not supposed to drink distilled water.”

Ah. Yes and no.

Distilled water is water that has been boiled, trapped as steam and condensed, leaving behind the non-volatile impurities (the stuff that doesn’t easily turn into a gas, like metal salts). Other components, like alcohols can still be carried along into the distillate.

Distilled water lacks most of the ions that tap water has, and thus, much of its flavor. Some of the ions (such as fluoride) in regular tap water may have health benefits, so a steady diet of distilled water may deprive you of certain useful trace elements. Conversely, drink water that is too hard (has a lot of ions in it) is correlated with kidney stones. It’s unlikely that the ionic content of your drinking water has a huge impact on your health (despite claims found here and there). All of the trace elements (including fluoride) can be found in other food sources. And distilled water’s osmotic pressure isn’t so different from that of plain water, therefore drinking it will not cause the cells in your body to suck up water until they burst and you begin to bleed internally (yes, this theory is out there, for both distilled water and deionized water). Bottom line, yes, you can drink distilled water.

That said, you probably shouldn’t drink the distilled water in most labs, as it is not tested to be free of bacterial contamination (which it can pick up in storage tanks) or volatile organic compounds. The same goes for bottled distilled water that hasn’t been tested to be certain it’s potable.

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And while we're on urban myths about water, it's impossible to completely remove all the ions from water. Water is always in equilibrium with hydronium ions (H₃O⁺) and hydroxide (OH^-).

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Image Copyright Filipe B. Varela, 2011. Used under license from Shutterstock.com

Urban Myths of Chemistry Redux: The Enantiomers of Thalidomide

A few months ago I mused about the persistence of an urban myth of chemistry - the meaning of the p in pH. The musings grew into an essay which appeared in Nature Chemistry in August. [Urban legends of chemistry, Nature Chemistry 2, 600 (2010) - caveat, you or your institution need to have a subscription]. The in vivo behavior of the enantiomers of thalidomide turns out to be grist for another persistent myth.

"Ryoji Noyori, who shared the 2001 Nobel Prize in Chemistry for his contributions to asymmetric synthesis, uses the tragedy of thalidomide to open his Nobel lecture: 'A compelling example of the relationship between pharmacological activity and molecular chirality was provided by the tragic administration of thalidomide to pregnant women in the 1960s. (R)-Thalidomide has desirable sedative properties, while its S enantiomer is teratogenic and induces fetal malformations. Such problems arising from inappropriate molecular recognition should be avoided at all costs.'

A close reading of these tales raises more than a few flags. Details differ — was thalidomide marketed for depression or insomnia or morning sickness or to prevent miscarriage? (No, yes, yes and no.) Here is another urban legend of chemistry — with multiple authoritative sources, varying in detail, superficially reasonable, persistent — and with an incredibly compelling plot line. Yet it's not true — as even the tellers acknowledge on occasion. Both forms are teratogenic when administered, as they rapidly racemize in vivo.

Why would chemists pass on urban legends (and ones known to be false, at least in part)? Carl Jung suggested that 'no intellectual formulation comes near the richness and expressiveness of mythical imagery'" ....[read the rest at Nature Chemistry]

Prof. Israel Agranat (whose paper about chiral switches I reference in the essay) wrote me to share that it's not only chemistry textbooks in which these myths circulate. He pointed me to examples, including this one, from the law literature:

Citalopram is a racemate... Such molecules are called chiral (from χειρ, a hand) because, like a pair of hands, they are mirror images which cannot be completely superimposed on each other. They are conventionally designated (+) and (-). It has been well known for many years that, despite their similarities, the two enantiomers may bind to different proteins and produce different biological effects. The most notorious example was thalidomide, which consisted of a (+) enantiomer which was effective to prevent morning sickness in pregnant women and, unknown to the consumers, a (-) enantiomer which was teratogenic and caused severe birth defects." — excerpted from Lord Hoffman's decision of the England and Wales Court of Appeal in the Escitalopram oxalate (Cipralex, Lexapro in the US) patent litigation, H. Ludbeck A/s vesus Generics (UK)

So why do we pass on the legends? My short answer is that resistance is futile!

Fiat Lux 1: On Fire for Quantum Mechanics

My sailboat's name is the Fiat Lux — "let there be light" in Latin — drawing from both my theological and scientific personae. I sail a Laser, an Olympic class racing dingy, which is an apt boat for a quantum mechanic. The ability to amplify light by stimulating an existing emission process was first predicted by quantum mechanics, then the apparatus to actually do it was built. Laser is really an acronym: Light Amplification by Stimulated Emission of Radiation. The radiation is electromagnetic radiation, not the radioactive radiation.

There's been a smattering of conversation about light production around my house this weekend between sailing the Laser, setting off fireworks and observing fireflies. One of my teen guests wondered how the fire in fire flies was different from the fire in fireworks. All light is not created in quite the same way....though there are some fundamental similarities.

There are really two fires in fireworks, the thermal explosives that send them skyward, and the "rockets red glare" — the glittering burst of color in the sky. The heat from the thermal explosion (usually blackpowder or a similar substance) is what trigger the colors.

If you ever done a flame test, putting a solid substance or a concentrated solution on a wire loop and placing it in a flame to see what color is produced, you've done the same chemistry. The extreme heat excites electrons in an atom or molecule, and as they fall back down to their lowest energy, or ground state, emitting a photon (a bit of light) that just exactly matches the difference in energy between the excited state and the ground state. An orange flame meant you had sodium on the wire, while a violet flame suggested potassium. More properly this technique is called atomic emission spectroscopy.

For atoms the picture you usually see in a high school text of this process is of a ladder, where electrons are shown moving from rung to rung. The larger the distance between the two rungs (or states) the higher the energy of the photon emitted. If the distance corresponds to photons in the visible region, you see a color, otherwise you have to use something fancier to figure out the energy of the photons being released.

Different atoms have different spacings between states and so the colors they emit when heated to high temperatures are likewise different. There are in fact many states, and so many types of photons can be emitted, but few are in the visible region.

If you click here, you can see a simulation of the photons you'd expect to see when an excited sodium atom returns to the ground state. Are you surprised that sodium can be used for yellow-orange in fireworks? Some urban legends suggest that lead (or radioactive barium) are used in fireworks, but if you look at the line spectrum of lead you can see why it can't be true -- there is no rung to rung jump in lead that corresponds to a visible photon. So a lead firework would be invisible! (Lead used to be used to make the fireworks "crackle"...)

(And it's true that barium salts are used in fireworks, but they are not radioactive. There are no naturally occurring radioactive isotopes of barium.)

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Read more:

An article at C&E News on the chemistry of fireworks

Related posts:

Jello lasers
Romancing the stone (lasers in the plot line of a romance novel)

Image from Wikimedia.

Warning, Dr. Smith! Warning!

An SF fan from the moment I discovered Heinlein's Have Spacesuit -Will Travel in the minuscule public library in the small (population 2500) Midwest town I grew up in, it's probably not a surprise that I would have been an avid watcher of SF on TV. When I get various 'urgent warnings' in my inbox, I often hear the Lost in Space robot's voice in my head, "Warning, Dr. Smith! Warning!"

A few days ago, this warning about the dangers of taking business cards from strangers appeared. Take one of these drug laden cards in your bare hands and soon you will be easy prey for swindlers and worse. Is such a thing possible? Can you be drugged against your will by briefly touching a drug?

In principle, yes. Unbroken skin, though a good way of keeping your insides in, is not an absolute barrier to molecules entering the body. Some molecules — such as DMSO — are better at getting in than others.

When I teach mathematical modeling, one topic we look at is ways to model diffusion. An application that many of my students find interesting are passive drug delivery systems that capitalize on diffusion. In other words - patches. To me this warning sounds like a folkloric riff on drug patches. In fact, delivery through a patch is a pretty complex system, it's not just a matter of soaking the equivalent of a gauze pad in a drug and taping it to your arm.

The drug cocktail purported to be on the business cards is burundanga - a mixture of two plant alkaloids, atropine and scopolamine. Both can be administered through the skin, when I had surgery a couple of years ago, the anesthesiologist use a scopolamine patch to manage my post-op nausea. But he didn't hand me a "don't throw up" card to hang onto for a few minutes in pre-op - that patch he applied behind my ear was a marvel of pharmaceutical engineering!

Burundanga has been used criminally but by slipping into a victim's food or drink. Incidental contact with atropine or scopolamine won't incapacitate you — though the prescribing information for the scopolamine patch points out that you should avoid touching the patch and then your eyes - resulting in dilated pupils and blurry vision.

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Scopolamine was used as an amnesia inducing agent during labor and delivery in the 60's. I suspect Betty Draper's halucinations during labor and delivery on Mad Men (The Fog, Season 3, episode 5).

Image is of belladona, from which atropine and scopolamine can be extracted.

Chemical Urban Legends: pH

What does the p in pH stand for?

The term pH has been in use for more than a century. It is a logarithmic measure of the hydrogen ion concentration ([H+]): pH = -log10[H+]. (Technically, there aren't bare protons (H+) floating around in solutions, but that wasn’t known when pH was introduced!) The original symbol used by Sorensen was p_H⁺.

Theories vary as to the origin of the p - most agree it means power but whether in Latin, French or German, seems in dispute. Thinking it would be either French or Latin as the original paper was published in French, I was surprised to find that it's neither, though the legend is both old and persistent. By 1920, many authors were assuming that it meant “power”, but Jens Norby returned to the original sources and points out that it was the arbitrary choice of the letters p and q for two variables in the work-up of the experimental data. The variable p eventually ends up in the formula arrived at for the concentration of the hydrogen ion.

The modern form pH was introduced in 1920, "as a matter of typographical convenience".

For the full explanation, see Jens G. Norby, The origin and the meaning of the little p in pH, Trends in Biochemical Sciences 25, 36-37 (2000). The illustration is a selection from the original paper: Sorensen, Compt. redn. du Lab. de Carlsberg 8 1-168 (1909).

Cold as Ice

This article in the Atlantic monthly caught my eye, if only because it included an experiment and less because of my refined palate. Wayne Curtis is writing about the unsung hero or villian of mixed drinks: ice.

"I went into the kitchen with another bartender, Stephen Cole, who hunted up a scale and thermometer. He placed the two kinds of ice into separate cups filled with water. We let them sit for 10 minutes. The cheater-ice water proved to be colder (34 degrees compared with 40 degrees), but the ice had lost a full quarter of its weight, compared with just a 14 percent loss in the chunk ice. A cheater-ice cocktail is thus chillier (numbing the taste buds) and more watery (making it flat)."

He describes a bar which stocks eight different types of ice - though the classification system is not quite what a physical chemist might use - or even Kurt Vonnegut. I suspect, however, a serious flaw in the experiment, and therefore in the conclusions drawn about the effect of ice type on a drink.

Take a mixture of ice and water that has been thermally isolated (put in a thermos!) and allow it to come to thermal equilibrium (let it sit until the temperature doesn't change any longer). When the contents of the thermos reach equilibrium, if there are both ice and water present, the temperature is 32 degrees (Fahrenheit). It does not matter how cold the ice was to start, how much water is present, how warm or cold the water was - it will be 32 degrees. Not 40. Not 34.

Also known to those who know how to read a phase diagram, ice at normal pressures will not start to melt until it reaches 32 degrees, and its temperature will not rise above 32 degrees until it has all melted. Curtis' experiment isn't quite as sophisticated as the thermos one I've sketched out, but assuming that the rate of heat loss to the room was small (air - or any gas - isn't a very good thermal conductor, so over the short term this is not a bad assumption), and that the ice and water used were pure, and that a very large amount of water was used relative to the ice - I find it untenable that the "cheater-ice" cocktail is different in temperature than the one made with less porous ice. More watery, yes, colder, no.

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Photography by Sue Stafford. Used under Creative Commons license.

Weird Words of Science: Hypsometer

Every time I write an exam, I think about this story, where a physics professor asks on an exam how to measure the height of a building using a barometer. A student answered that he would tie a string to the barometer, lower it down, then measure the length of the string. Given no credit, he protests, and the professor offers him a second chance to provide an answer that is both correct and demonstrates some knowledge of physics taught in the course. The student goes on to give several answers (in some versions the student is averred to be Niels Bohr - though the origin of the story is apparently in a textbook on the teaching of math and science by Alexander Calandra, and unrelated to Bohr) all demonstrating a knowledge of physics, and none the one he seems to know the professor is fishing for (which has to do with the - probably unmeasurably small - pressure differential between the ground and the top of the building).

Here is a chemistry exam question I sometimes ask - how would you measure the height of a mountain with a thermometer? This is a well-known technique,not a trick question, the apparatus is called a hypsometer, from the Greek for "height-measure". The underlying science is that the boiling point of a liquid changes in a known way with altitude. Hypsometers were used before portable aneroid barometers became widely available, and were used in high altitude balloon measurements of pressure as late as the 1960s.

Bonus question: Is it easier to drink a liquid using a straw at the top of Mt. Everest or on the beach in Florida? (Disregard temperature differences and explain your answer for full credit!)

Breathing Deeply

The tunnels deep beneath New York that bring crystal clear water from the reservoirs upstate to the city are aging. Divers are busy assessing the infrastructure - and it's literally a high pressure job. In order to avoid time consuming daily decompressions, the divers are living in a high pressure environment for weeks at time, almost 20 times normal atmospheric pressure. As AP reports, the pressures require that the men breathe a helium-oxygen mixture. Unfortunately, the reason given in the article for breathing the squeaky voice inducing mix: "the nitrogen in regular air is too heavy at 600 feet and their lungs could not handle the pressure." is utter nonsense.

Nitrogen does not weigh more under pressure, and the total pressure of the gas in the divers lungs is high, regardless of the identity of the gas (oxygen gas weighs more than nitrogen does, in fact). The real reason has to do with Dalton's law of partial pressures, and the fact that at high pressures, neither oxygen nor nitrogen are benign substances.

Dalton's law says that the pressure of each gas in a mixture is a function of the percentage of that gas and the total pressure of all the gases. For example, at 30,000 ft, where the total pressure is 0.3 atm and the fraction of oxygen in the air is 21%, the partial pressure of oxygen is 0.063 (humans need a partial pressure of about 0.1 atm to oxygenate their blood).

At the depth of the NYC tunnels, the total pressure is just over 18 atm, so the partial pressure of oxygen would be 3.8 atm. Above a partial pressure of roughly 1.5 atm oxygen gas is seriously toxic. The partial pressure of nitrogen 600 feet below the surface is about 14 atm. Nitrogen narcosis, rapture of the deep, sets in at pressures above 4 atm. At these depths, nitrogen is essentially an anesthetic!

Introducing an inert gas into the breathing mix, such as helium, reduces the percentage of oxygen and nitrogen in the air, thus reducing their partial pressure and reducing the danger of oxygen toxicity and nitrogen narcosis. The need for the specialized breathing mix has nothing to do with the heaviness of the nitrogen and everything to do with the toxic effects of these gases at high partial pressures.

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Eliminating nitrogen completely from the mix can also reduce the potential for developing the bends (bubbles of gas that form in the tissues when pressure is reduced) - but that has to do with Henry's Law and ladies corsets, and is another blog post!

Tin tears

Tin cries. Not tears, but when tin is bent it elicits a peculiar sound called by metallurgists a "tin cry". Indium also lets out a scream when deformed, as Michael Cassidy pointed out in an earlier comment.

You are hearing the sound made by a phase transition, a change in the structure of the metal at the atomic level. Indium in its crystalline form is tetragonal, when bent, the mechanical stress induces "twinning" in which sections of the crystal become mirror images of adjacent planes. Twinning plays a role in mechanical failure of metals subject to stress, the research literature goes back roughly a century.

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Listen to a recording of indium "screaming" made by Theodore Gray at the WGBH studios. It's an unnerving sound, more like a crackling than a scream.

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The photo is courtesy of David Hammon in the physics department at the University of Vermont.

Dandelion Wine

At a party Saturday night someone mentioned a rumor about extracting illegal drugs from dandelions. This was news to me, I hadn't thought that dandelions had all that much to offer pharmacologically. Google didn't produce any hits, nor did my students know anything (though they did tell me that on MythBusters they'd made nitrous oxide from ingredients you could obtain at home). There is some evidence from rat models that dandelion extracts can interfere with antibiotic absorption (particulary those in the same class as ciprofloxacin), and it has potential for control of blood sugar, but I can't find anything in PubMed more interesting than that.