A high-school teacher in New York set two of her students on fire on Thursday. One of them is in critical condition after “a snakelike flame tore through the air … searing and melting the skin on his face and body.”
It was an experiment gone, horribly, tragically wrong, and this particular experiment—a methanol flame test—goes horribly, tragically wrong with unsettling regularity. A New York Times story on Thursday’s accident includes a paragraph that starts with the never reassuring phrase “Other cases when the demonstration caused an explosion and fire …” Three weeks ago, a government safety panel, the Chemical Safety Board, released a video and warning message about the same experiment. The CSB’s video features yet another student who was severely burned when a methanol flame test set her on fire.
A school official in New York said of Thursday’s accident, “We’re determined to get to the bottom of this so that it never happens again.” But the mechanism of injury in all of these cases is not hard to understand. A flame test analyzes an unknown substance by determining what color flame it produces when it burns. Flame tests make for vivid demonstrations because of the different colors different substances produce, and because of the human (and adolescent) fascination with fire. There are many kinds of flame tests; a common demonstration setup—and the one that exploded on Thursday—uses methanol as an accelerant. Methanol is highly flammable, making for bigger flames; it also burns invisibly, allowing the different colors emitted by the minerals being burnt to stand out.
Unsurprisingly, the properties that make methanol attractive for flame tests also make it dangerous. Large and invisible flames are not to be trifled with. Methanol also has other propensities that make it especially hazardous in a classroom setting. Although it is a liquid at room temperature, it has a high enough vapor pressure that it spreads easily into the air—and a low enough flash point that it ignites easily once it is there.
The dangers of methanol flame tests are well-enough understood that there are extensive safety instructions for anyone trying to carry one out. Flinn Scientific’s demonstration videos on YouTube are hair-raising, and so is the page-long “Safety Precautions” section of its instructions for the flame test. And yet, the injuries keep on happening: an investigator with the CSB said, “What we need to look at is why is this accident keeps happening across the country. … I can’t imagine a teacher would do this demonstration if they knew the potential risk they were putting students in.”
One reason may be that methanol flame test—sometimes called the “rainbow”—has a long history in classroom demonstrations. It seems to be part of the folklore of high school chemistry teachers. Even one of the Flinn Scientific videos leads off with a wistful note about the demonstration’s historical significance—a little like the Onion’s Fun Toy Banned Because Of Three Stupid Dead Kids. That history, and with it the assumption that something so familiar could not also be so perilous, may be one reason the CSB’s message is not getting through.
Consider what the CSB is up against. High school chemistry teachers don’t just wake up one day and say, “Hey! Why don’t I spritz some methanol on burning metallic salts to demonstrate emission spectra?” They get the idea—and and the laboratory procedures—from somewhere. And not all of these sources are careful about the safety side. Here are a few of the horrifying things I found on the Internet yesterday:
- YouTube videos of flame tests brazenly violating multiple basic safety precautions. (The dishes aren’t well separated, there are no lids by the dishes, and the teacher is wearing neither gloves nor an apron.)
- A lab report template for students to carry out methanol flame tests, and lab reports from students who had done so. Again, the directions violate crucial safety directives. (The first instruction in Flinn’s guide says not to use watch glasses, as “the methyl alcohol can easily spill out and spread the fire.”)
- Demonstration instructions that omit almost all of the safety precautions.
These are not random blog posts by home chemists (although there are plenty of those, too). These are science educators reporting on their own unsafe practices, and encouraging others to do as they do. These are professional chemists. They know what methanol is and does: that’s why they’re using it. But none of them seem to have any sense of how easily methanol flame tests can go wrong, or how badly someone could be hurt.
Where might this cavalier classroom culture come from? Here are two of several alarming articles from the Journal of Chemical Education I also found yesterday. Both were published as “Tested Demonstrations” in “the world’s premier chemical education journal,” the flagship journal of the education section of the country’s professional society for chemists.
Maynard, J.H., J. Chem. Educ., 2008, 85 (4), p 519 (“Using Hydrogen Balloons To Display Metal Ion Spectra”)
Abstract: We have optimized a procedure for igniting hydrogen-filled balloons containing metal salts to obtain the brightest possible flash while minimizing the quantity of airborne combustion products. …
Johnson, K.A.; Schreiner, R., J. Chem. Educ., 2001, 78 (5), p 640 (“A Dramatic Flame Test Demonstration”)
Abstract: A dramatic ball of colored fire appears when a salt/methanol mixture is sprayed into the flame of a Meker burner. The colored fireball is highly visible, even in large lecture halls. Although the fireball has a short duration, it can easily be recreated by repeated spraying of the salt/methanol mixture into the burner. The equipment for these striking flame tests is easy to prepare and store.
There is more in this vein, much more. I would like to think that these articles are reaching an audience capable of recognizing the remarkable danger of such demonstrations, and taking appropriate precautions. The frequency with which students and teachers are burnt in methanol flame tests suggests otherwise.
When I started researching the methanol flame test, I expected to find a story of changing safety standards, or of an influential but outdated book still in the teachers’ section of school libraries, or of a few teachers deliberately cultivating a devil-may-care attitude. I found none of these things. Instead, a few hours after asking, “Why would a teacher give such a dangerous demonstration?” I had an answer that left me even more worried than before. No one told her not to.
I will give the last word to lab safety consultant David J. Leggett, as quoted by the New York Times:
I would frankly question the use of methanol in an experiment that is simply going to say look kids, look at the colors.