From sci.chem Tue Nov 12 18:30:40 1996 From: "Stephen L. Gilbert" Newsgroups: sci.chem Subject: Re: Lab Accidents....... Date: Sun, 10 Nov 1996 21:31:16 -0800 Organization: Consulting Services > > In wpenrose@interaccess.com (William R. Penrose) writes: > > >2. Another time, I was making trimethylarsine with methyl magnesium iodide > >and arsenic trichloride, in an n-butyl ether solvent. The TMA boils at 50C > >and is distilled off from the higher boiling nBu ether. Except it didn't > >boil. It just got hotter and hotter. Well, everyone in the lab was nervous, > >and I was the most nervous. I realized that the magnesium iodide precipitate > >in the flask was not going to act as a boiling nucleation, so I cleverly > >dropped a boiling stone in through the condenser. In about three seconds, the > >flask was empty, all over the inside of the hood. There was a stampede out of > >the lab. I stayed for a minute to close the windows so that the discharge > >from the hood wouldn't blow back in, and my coworkers thought I had been > >killed until I came out still holding the breath I had taken when the flask > >blew. > The heavy form of a BOD (biological oxygen demand ) is a chemical oxygen demand, a digestion with mixed chromic and sulfuric acids at the boiling point. You mix a measured amount of chromic and sulfuric acids, a measured amount of the sample, add them to a boiling flask, add a boiling chip, install a reflux condenser, place in a heating mantel, turn on and walk away for a couple of hours. Well, if you don't mix...the chromic and sulfuric acid layer is so viscous and dense, it just doesn't mix...and just doesn't boil until way way above 100 C ! When it bumps, the entire contents of the flask exits via the reflux condenser, travels across the room and eats a hole in whatever it encounters along the way....coming back from lunch one day...BOOM !! and was lucky enough to be a few seconds too late to catch it in the head ! -- Stephen L. Gilbert Consulting Services........"serving the Semiconductor Industry" 3631 N. Hash Knife Circle Tucson, Arizona 85749 browse http://www.goodnet.com/~conser for more infor