Many years later i came across this story - which i adapt - recounted by Eduardo Galeano in The Book of Embraces (WW Norton, 1989, p. 158):
Once a professor brought a small bottle of some clear liquid to his class and which he placed on a desk at the front of the room. He explained that he wanted to do an experiment. The bottle was filled with a liquid and he wanted to see how fast the odor dispersed across the room once the bottle was uncorked. Each student was to report when they smelled the odor. He uncorked the bottle and after a few minutes a student in the front row said that he could smell something. A moment later students in the second row reported that they could definitely smell the odor. More and more students reported the odor. One said that it was very strong and not that pleasant. Finally all agreed that they could smell the odor and one student in the back coughed and asked to open a window to relieve the air. Afterwards the professor asked to students to come up one by one. He poured a bit of the liquid on each of their fingers and asked them to taste it. The liquid was water.