One of my least favorite chemicals is ammonia. Described by most as that pungent smelling gas, it is one that I would always prefer to avoid if I could. Not as downright unpleasant in aroma as numerous sulfides or mercaptans, it has instead a kind of olfactory kick in the sinuses that makes you instinctively jerk away.
What is a shame is that it is quite a useful little molecule – as the long list of producers and uses on its Wikipedia page testifies. The main use in synthesis is for dissolving metal (usually sodium) reactions, which have a characteristic (and quite beautiful) blue color. A more every day use is as an addition to chromatography solvents as ammonium hydroxide, to help the march of the amines through the silica. So my distaste for its pungency has taken a back seat to my appreciation of its utility.
My time at graduate school (at the picturesque University of St. Andrews in Scotland, by the way) was book-ended by ammonia releases that prompted evacuation of the building. I should add that I wasn’t involved in either, other than as bystander, but my understanding was that the cylinder of ammonia was only infrequently used (as would be obvious if you consider they had the same one at the end of my time there as they had at the beginning!) and had a tendency to get a bit stuck, only to open all at once and release a whole lot of ammonia in one go. Why they didn’t just get rid of the thing after the first time, I have no idea.
A more serious incident also occurred in my group while there, a grad student using ammonia got a face full after a septum popped out. It was pretty scary for a moment or two, but a colleague in the lab at the time grabbed him and got him to the sink, giving him a thorough drenching. Within a few minutes, he was all right again. It was quite shocking how suddenly something can happen in a laboratory like that. One moment as quiet as can be (given the noise of the hoods, pumps, etc), next moment bedlam breaks out.
I have done the sodium-ammonia reaction myself several times. I can’t deny it is pretty, but it is a real pain to carry out. In fact, one assignment I was given was to eliminate the sodium-ammonia step from a reaction sequence. This particular reaction was a worse pain than most, as not only was it procedurally tedious, it also didn’t give that great a yield either. But the constraints on the available space and glassware meant it could not be scaled up to any great extent either, so it became a bottle neck in the synthesis, one I was more than happy to circumvent.
Plus, it smells. Did I mention that?