This afternoon I did a demo for one of my classes which involved heating up solid sulphur over a Bunsen burner until it started to burn in air, then immersed it into a pure oxygen environment to generate sulphur dioxide. Then, when you add a little water, the sulphur dioxide reacts with it to form sulphurous acid; if you add a little bromthymol blue it turns yellow, to show it is, in fact, an acid:
1. S(s) ----> S(L)
2. S(L) + O2 (g) ----> SO2 (g)
3. SO2 (g) + H2O(L) ----> H2SO3 (aq)
Have you ever smelled sulphur dioxide? ("Rotten egg" gas is hydrogen sulphide, H2S(g), which is close, but no cigar.) Sulphur dioxide stings and burns, and smells really quite awful. It gets in your nose and throat, and even if you use the fume hood (which I did) to take away as much of it as you can, it seems to linger for a while.
Long story short, it's after 10 p.m. and I can still smell/taste SO2.
I love/hate my job.