by
lmh » Fri May 06, 2011 12:49 pm
In many cases it's what you do with a chemical, rather than the chemical itself, that determines the hazard. That dihydrogen oxide stuff is a case in point: water has been a major cause of more industrial accidents than any other chemical, but many of its accidents result from the extreme danger of large amounts of steam under pressure. It is also quite reactive stuff, but it takes two to make a reaction (usually).
During my career I've had difficulties with methanol, and more recently I've had a situation where I had to argue for some weeks before it was accepted that I could dispose of up to 1 L of 0.1% formic acid in water down the conventional lab drain. Even less logically (considering the vinegar-consumption of our organisation's cafeteria), 1L of 1% acetic acid in water was considered a hazard that could not go down the drain. The arguments were that it might influence the overall pH of the waste from the entire building (800 employees...), and it would unacceptably increase the total organic content of the waste.
There's a strange psychology about this. Many, many years ago, now, I remember doing a lot of work with 14C. At the time, local regulations were to dispose of aqueous 14C down a specially-designated sink, which led to conventional drains, but records were kept of how much went down there, and someone calculated the dilutions. Meanwhile, we used triton-toluene based scintillation fluid, which is hardly environmentally friendly. We changed to an ecologically more acceptable fluid, that (according to its manufacturers) could be disposed of in normal sink waste. This was banned, flatly, by the local water authority. We could dispose of this scintillant down the sink if it hadn't been mixed with radioactivity, and we could dispose of radioactivity down the sink, but we couldn't dispose of used scintillant down the sink because it had been mixed with radioactivity. Go figure. The critical panic-inducer was, of course, "radioactive material", but whoever took the decision about scintillant was blissfully ignoring the fact that we were already putting 98% of our 14C down their drain anyway. I'm grateful not to work in that field any more.