Dimethylmercury (All gloves are not created equal)
8th May 2006
Mercury is a weird one. It’s quite toxic, and you’ll do well not to handle it casually, but as the metal it’s actually not that bad. If a thermometer breaks, you can probably clean up the area as best you can, then sprinkle zinc dust or sulfur (disputed, see here) on it to keep it from evaporating. If you spill it in, say, an oven, like in the lab, or spill a great deal, it can be a bigger problem - some labs have mercury bubblers with literally pounds of the stuff in them - for most applications, you can use mineral oil, but especially in academic labs, you see a lot of mercury still floating around.
Mercury metal, though, just isn’t what we’ve made it out to be. It’s unique in that it’s a little volatile, and most metals aren’t, but its toxicity isn’t exceptional. Every fluorescent bulb in your house has a few tens of milligrams of mercury in them - this is why you’re supposed to recycle them. That said, eating some mercury or inhaling it certainly isn’t going to improve you, and it’s something to be treated with respect. I only say it’s not-so-bad because where it really gets nasty is compounds of mercury: Mercurous nitrate, or Hg+NO3-, was the compound used by hatters on beaver fur. Mercuric chloride, or Hg2+Cl2, is used in labs for various reasons. One is making guanidines:
These are much worse, since they’re water soluble. Even worse are organomercury compounds - dimethylmercury is the one we most often encounter. This is what killed Karen Wetterhahn - a story just about everyone who works near mercury knows - and also the “mercury” you find in fish. Bacteria convert mercury metal in streams (from improper disposal, yes, but the funny thing is, large amounts of this come from the combustion of coal - it’s trapped in there.) into dimethylmercury, plankton eat them, fish eat them, bigger fish eat them, and so on. This is why the really big fish are the bad ones.
Back to polarity again! Dimethylmercury is so bad because it’s nonpolar and lipophilic. It gets a free ride even across protective gloves - Karen Wetterhahn was wearing latex gloves at the time - not even neoprene is quite enough.
Whatever they’re paying you to work with this stuff, it’s not enough. Ugh.