When it comes to the potency of the odor of thioacetone, it seems to me there are two issues of interest: detection and dilution.

1. The first question is how detectable is thioacetone to the human nose, that is how many molecules are actually needed before someone can actually detect it? The second is, is thioacetone the most detectable molecule known to us, if not then what is it?

It seems to me these are important questions for various reasons. Determining the absolute sensitivity or limiting resolution of our sense of smell could be tied up with out ability to detect† thioacetone. Then there's the question of how our sense of smell compares with other animals, dogs for instance. Dogs are renown for their acute sense of smell and we know they have many more smell receptors hence the acuity of their sense compared with humans. My question is do dogs' receptors have the same level of resolution (molecules versus detection) as do humans and does that change from molecule to molecule? Experts please let us know.

If these facts are still not well understood then perhaps thioacetone may be a good research tool for the purpose.

† Incidentally, it seems to me we've a similar issue with our ability to taste stuff, for instance, the chemical denatonium (Bitrex) is the most bitter substance known to humans and humans can detect it in extremely small amounts. However, the extreme sensitivity of humans to the chemical doesn't necessarily apply to other animals, rats for instance, which makes it a good denaturant for rat poisons, etc.

2. The matter of dilution. It seems to me that our experience of dilution is a bit like exponentiation in that our human sense of scale doesn't work very well when things change at exponential rates. Exponentiation often catches up with us because its effects/actions are 'outside' our normal daily (human) experience. Well, I reckon dilution is a bit like that (certainly so at the edges).

We often wash stuff away until there's seemingly nothing left of it and we think it's gone but as chemists know this is often far from being the case. I learned this the hard way as a kid when doing photography after I'd failed to leave my prints in running water sufficient time to wash away all the hypo (if I recall the recommended washing time was 5 minutes and I only washed for about a third that time). The prints looked perfectly OK for some hours afterwards but by the next day, they'd gone a horrible brown color. A lesson learned: insufficient removal of unwanted chemical can be problematic even when there's seemingly precious little or no obvious trace of it left. The fact is it's often very difficult to dilute stuff to the point where its effect is truly negligible.

It seems to me that in daily life we've very little idea of (and pay very little attention to) the amount of unwanted stuff that remains after we, say, have washed something clean. In practice we've very little idea of how much of residual chemical remains in a container after it's been washed and cleaned and is eventually transferred to a new and different solution when the container is reused. Getting a feel for cleanliness, purity and impurity of substances, residues etc. is a lot harder than it seems for we fail to consider the fact that there are a great deal more molecules involved in processes than we can actually comprehend (or are cognizant of in the mental sense). That is, if something is diluted well past the point where we can see or smell it then we've a tendency to assume that very little or nothing of consequence remains whether it's in fact true or not.

It seems to me that thioacetone is almost the quintessential chemical to demonstrate dilution, impurity, presence of residual molecules etc. by virtue of the fact that it's so easily detectable in only trace amounts. The fact that it isn't dangerous at levels long past where humans can detect it—and given how bad it actually smells would make it useful (and very memorable) for such training exercises.

No doubt strict protocols would apply to the conducting of such lessons.