Dangerous Work Environment

mercury.gifThe other day, I posted about the dangers from mercury in broken low-energy light bulbs (CFLs). Today, I found that maybe I’m much closer to another source of mercury.

I work as a geologist in geotechnical engineering. My office is in the front of the building – white collar alert ! In the back is the lab – blue collar alert ! Whenever I feel like a break from mind numbing white-collar challenges, I venture into the world of rock/soil testing going on behind the closed doors of our lab.

When I got out of school, I had learned a great detail about days gone by – from Cambrian to Pliocene, but I knew very little about engineering applications of geology. Although I’m still not actively involved in much of the testing at our lab, I have learned a few things about how the tests are run, both by watching and reading. Today, I saw something I hadn’t seen before…

Our lab manager hands me a plastic bottle – probably about 12 oz and says: “Here, take this.” – I am confused, suspicious of some ploy to exploit my white collar ignorance of blue collar tricks. “Take it.” – I reach out and grab the bottle, and – WOW – it’s super heavy. “What the heck is it ? Lead beads ?” – “Mercury.” – “Holy crap! Isn’t that dangerous?” – “No !?”

Mercury has a specific gravity of 13.5, i.e. 12 oz of mercury weigh 13.5 times as much as 12 oz of water, which – if my algebra isn’t too rusty – is about 10 lbs ! Anyway, that much just on the side. I was very surprized, if not to say shocked to find that we keep mercury around, and was completely flabbergasted when our lab manager, wearing rubber gloves, unscrewed the bottle cap and poured mercury into a small ceramic bowl. – “What are you doing?” I stammered, gasping for air, sure that we would be poisoned in a matter of seconds.

Mercury has a volatility of  0.056 milligrams per hour per square inch. I read the other day that there is less than 5mg of Hg (mercury) in CFLs. So for that to evaporate, it would take approximately 100 hours, which makes mercury a really-not-that-volatile substance. The dangers really stem more from ingesting the element than breathing it in. Anyway, I watched for a few minute while he continued his experiment, till I turned blue from holding my breath.

Turns out that a common use for mercury in the lab is for accurate volume measurements of something like a small rock or soil sample. You fill a bowl with mercury till the surface of the liquid metal is flush with the rim of the bowl, then you submerge your sample in the mercury, and collect that portion of the mercury the spills from the bowl (it is recommended that spillage occurs into another container !). By weighing what’s spilled and knowing the density (specific gravity) of mercury, you can determine the volume of mercury that was displaced by your sample. Pretty smart, huh ? You use mercury because it doesn;t evaporate easily and because – being a metal rather than some other fluid, it doesn’t stick to anything and does not fill any pore space of a porous sample.

It was an interesting lesson in lab testing. But I did feel better once I headed back to the office – away from the poison. Lesson learned: don’t drink mercury, but don’t fret it tooooo much either.


One Response to “Dangerous Work Environment”

  1. When I was a kid I played with mercury on the kitchen table. But knowing what I know now I wouldn’t want to handle it…

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s

%d bloggers like this: