Why you absolutely should NOT mess with Di-Methyl-Mercury.

We have hear about dangerous chemicals all the time, and our chemistry lab instructors of high- school and college have warned us about potentially dangerous compounds and using lab reagents carefully. Most of the chemicals chemistry graduates deal with are not considered drastically dangerous, sure, concentrated mineral acids will punch a hole through your flesh, but that’s all they will do. That’s why we use gloves and lab coats.

Bromine gas will burn the insides of your lungs and chlorine gas will make you suffocate and cough. That’s why we use fume hoods, masks and eye protection.

Some compounds are carcinogens, and can be absorbed through skin if touched. We avoid contact by using gloves again.

These risks are known to a common chemistry student and he/she is appropriately instructed to avoid such toxic, carcinogenic, conspicuously dangerous compounds.

But there is a compound that takes the word ‘dangerous’ to a whole new level. This could just be one of those toxins CIA or KGB might use to assassinate somebody in a spy movie. (Or real life, who knows?)

This compound is Di-Methyl-Mercury.

Spacefill model of dimethylmercurySkeletal formula of dimethylmercury with all hydrogens added

Sure, the ‘Mercury’ in it should have alarmed you that this is dangerous by default. But conventional mercuric salts …are…salts. They aren’t going to penetrate your skin and cause sever mercuric poisoning. This compound is a liquid, not the silver heavy pure elemental Mercury that you liked to touch when you saw a barometer for the first time, but a colourless volatile non-polar liquid that can kill at absorption dosage as low as 0.1ml. That’s just one drop. One, tiny drop.

This is also a volatile liquid, whose fumes are enough to kill you.

Just to demonstrate how toxic this compound is, read this story on Dr. Karen Wetterhahn, a professor at Dartmouth College working on toxicity of Dimethylmercury, whose death is considered a textbook case in the toxicology community.


” On August 14, 1996, Karen Wetterhahn, a specialist in toxic metals, was studying the way mercury ions interact with DNA repair proteins, and was using dimethylmercury as a standard reference material for 199Hg NMR measurements. Dimethylmercury is a synthetic compound used almost exclusively as a reference standard in a particular type of specialized chemical analysis. Wetterhahn was investigating the toxic properties of another highly toxic heavy metal, cadmium.

Wetterhahn would recall that she had spilled one or two drops of dimethylmercury from the tip of a pipette onto her latex gloved hand. Not believing herself in any immediate danger, as she was taking all recommended precautions, she proceeded to clean up the area prior to removing her protective clothing. However, tests later revealed that dimethylmercury can, in fact, rapidly permeate different kinds of latex gloves and enter the skin within about 15 seconds.The exposure was later confirmed by hair testing, which showed a dramatic jump in mercury levels 17 days after the initial accident, peaking at 39 days, followed by a gradual decline.

Approximately three months after the initial accident Wetterhahn began suffering brief episodes of abdominal discomfort and noted a significant weight loss. The more distinctive neurological symptoms of mercury poisoning, including loss of balance and slurred speech, appeared in January 1997, five months after the accident. At this point tests proved that she was suffering from a debilitating mercury intoxication. She was admitted to the hospital, where it was discovered that the single exposure to dimethylmercury had raised her blood mercury level to 4,000 micrograms per liter, or 80 times the toxic threshold. Her urinary mercury content had risen to 234 µg per liter; its normal range is from 1 to 5 and the toxic level is > 50 μg/L.

Despite aggressive chelation therapy, her condition rapidly deteriorated; three weeks after the first neurological symptoms appeared, Wetterhahn lapsed into what appeared to be a vegetative state punctuated by periods of extreme agitation. One of her former students said that “Her husband saw tears rolling down her face. I asked if she was in pain. The doctors said it didn’t appear that her brain could even register pain.”Wetterhahn was removed from life support and died on June 8, 1997, less than a year after her initial exposure.

There had been previous documented cases of death due to dimethylmercury poisoning. In 1865, two English laboratory assistants died several weeks after helping to synthesize dimethylmercury for the first time. In 1972, a 28-year-old chemist in Czechoslovakia had suffered the same symptoms as Wetterhahn after synthesizing 6 kg of the compound. “



Only a few drops of this compound, being apolar, penetrated her latex gloves in SECONDS and absorbed by the skin. This is why it is so dangerous, because latex, PVC, neoprene gloves do very little to stop it, rendering gloves and lab coats useless.

So where would chemistry graduates might find this compound? NMR spectrometry of course. The students of Analytical Chemistry, and hence, Bio-Analytical Sciences should be aware of this highly toxic compounds used for NMR standards. It is unlikely that usual chemistry graduates will come across this compound, so there is no real danger, but this article high lights that how just a few drops of a compound can be lethal even with the safety standards. Chemistry lab is a place that people should respect, not because for discipline or that it irritates the teachers, but because it could be potentially, and will be, dangerous to lives.

Written by Aditya Karmarkar.


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