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Noxious Chemicals

December 14, 2014

A couple of days ago, there was a brief article on CBC news about a chemical that was removed from a laboratory by the bomb unit.  The article contained so few details that I could not guess what  chemical this was.  I was a lab technician in my first permanent job.  We did use a number of noxious chemicals there, but none of them could become explosive by themselves.

My first job was in a soil analysis lab.  It was essentially analytical chemistry adapted to the requirements of Soil Science.  Most of the reagents we used were rather benign, although at times we did use strong chemicals.  We were aware of the risks, and did take precautions when necessary.  We didn’t have all of the protective clothing that technicians wear now, but we did have lab coats and rubber gloves.  We were careful to avoid spills.  Whenever we were evaporating something that gave off a corrosive vapour, we did it in a fume hood.

I recall some of the hazardous substances that we used:

  • 30% hydrogen peroxide.  We used this to oxidize organic matter in soils.  It feels just like water on your hands, but in a few minutes, you will notice a tingling sensation there.  When you look at your hands, you will see white patches where it wet your hands.  We quickly learned to wash it off if it got on our hands.
  • Perchloric acid.  We had a special fume hood built out of asbestos-cement board and stainless steel so that we could evaporate perchloric acid safely.  I recall neutralizing it on an automatic titrator attached to a pH meter.  The meter was calibrated from zero to 14, but when the electrodes were first placed in the perchloric acid solution, the pH went below zero.  I’d never seen that before.  We were all aware of the risk of explosion when organic material like wood was allowed to absorb perchloric acid fume.  We were careful with that stuff.
  • Hydroflouric acid.  We used this reagent to dissolve silica, in teflon or platinum crucibles, needless to say.  Hydroflouric acid is quite dangerous.  It’s absorbed by the skin, but it’s painless, leading to severe burns later on.  We were aware of the dangers, and made sure we always wore rubber gloves while handling this chemical.  I had no problems with it, but I did hear of one technician who did receive some burns that required medical attention.
  • Ammonium hydroxide.  This chemical came in cases of six four-litre bottles.  We kept them on shelves in a basement room.  I recall one time I knocked a bottle off the shelf onto the concrete floor while I was reaching for another chemical on the same shelf.  The ammonia fumes filled the room.  I got out of there quickly, and told another technician what I had done.  He went down there to clean up the mess.  I didn’t expect that response.  I suppose all it took was lots of water to flush the chemical into the floor drain.  In any case, I didn’t see it until it was all over.
  • Sodium hydroxide.  This chemical came in white pellets that we dissolved in distilled water to make the correct solution.  It had a soapy feel on your hands.  That’s because it was reacting with your skin to create a soap.  We quickly learned to keep that reagent off our fingers too.

I suppose we were fortunate that all our accidents were minor ones.  Certainly, nothing ever exploded, or presented a risk of explosion.  We were aware of the risks, and that meant that we showed proper respect for the noxious chemicals.  All in all, it was an enjoyable and exciting part of my life.


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