csua.org/u/9l9 -> www.corante.com/pipeline/archives/2004/10/20/ping_ping_ping.php
I was using hydrogen chloride gas straight out of the cylinder today, fir st time I've done that in many years. That's a very different substance from regular hydrochloric acid, which is technically a solution of HCl g as in water. The straight stuff will really snap your head back if you g et a whiff of it, which you'd better not since it does Bad Stuff to your lungs, as you'd imagine. You need to rig up a trap for the vented gas, since it's rather bad form just to send it up the fume hood. The standard way is to bubble the exce ss through aqueous base to neutralize it, preferably rigged up so that t he water doesn't have a clear path to go siphoning back into your reacti on if the pressure goes haywire. Bubbling the HCl into a solvent like me thanol always looks a little odd. You can send a pretty vigorous stream of the gas in one side and have very little coming out through the trap at all, since the methanol is soaking up so much of it. These gas cylinders are under pressure, and the large ones look just like the helium tanks that non-scientists are familiar with from balloon ven dors. The regulator valves on top of them need to be made of rather more robust material for an HCl tank than for helium - which is, after all, totally inert under all conditions short of the interior of the sun. Bac k in grad school, a corroded regulator (on a whopping big HCl cylinder) gave me a real scare as it threatened to give way and vent all the gas a t the full tank-neck pressure of about 1500 psi. But today's work was with a lecture bottle, a much smaller cylinder that holds only a couple of hundred grams of the gas. That's enough to do som e damage, true, but not on the scale of the free-standing ones. One day I was sitting in the library, looking up some references, when I noticed the occupants of the third floor research labs pouring out onto the lawn from the rarely-use d side stairwells. They were hustling right along, too, which suggested some sort of liveliness upstairs. One of the guys ha d another HCl tank, a medium-sized one, which was also corroded and jamm ed. He went for the cylinder wrench, which he then used for the non-stan dard purpose of vigorously whanging the valve with strong overhand strok es. One of the other guys in the lab summed up the sound of this process as "PING. " The hood wasn't enhanced by having a kilo or two of hydrogen chloride ven ted all over it, that's for sure. It looked as if it had been subjected to some sort of accelerated aging process - if there were a market for a ntiquing lab equipment, this would be a good way to do it. All the expos ed metal was pitted and flecked with green. The stainless steel was haze d with rust, having reached its carrying capacity for corrosion. And eve rything still had a fine mist of concentrated hydrochloric acid all over it where the gas had sucked the water out of the air and condensed on t he nearest surface. Cleaning it up is not the way you want to spend your Friday afternoon. I ran the stuff in uneventfully, with the reaction turning to a clear yellow, which is nothing compared to the colors I'd turn if you sprayed that much on me. I'll find out tomorrow if things have worked according to plan. cgi/50 91) That may have been the most horrifying story I've heard from you yet, Der ek. Does anyone have anyone good stories about out-of-control gas cylind ers? I've heard they're like torpedos, but I've never actually seen one in action.
Permalink to Comment As a non chemist, I wonder how often really bad things actually do happen to chemists. Has anyone ever l ooked at occupational injuries of chemists and compared them to, say, ro ad construction workers? How about looking at long term cancer rates for the profession? I think I would like to know these things if I was a ch emist.
Permalink to Co mment Y'know, it's not a job without hazards, but the last data I recall seeing were pretty reassuring. No increased cancer risk, and pretty long life expectancy - I'll try to dig up the figures. Of course, if you happen to run into the wrong compound, that could change.
Permalink to Comment Derek, I am surprised you saw data showing no increased cancer risk. I ha d always been extrapolating from the old school we-bathe-in-benzeze days , assuming there must be some greater incidence of cancer.
About this author Derek Lowe mugshot Derek Lowe, an Arkansan by birth, got his BA from Hendrix College and his PhD in organic chemistry from Duke before spending time in Germany on a Humboldt Fellowship on his post-doc. He's worked for several major phar maceutical companies since 1989 on drug discovery projects against schiz ophrenia, Alzheimer's, diabetes, osteoporosis and other diseases.
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