Another day in the lab

Today I set aside a chunk of time for students to do a lab. I took the
opportunity to use up some excess solutions from previous labs.
Unfortunately, due to a spill in the lab, we ran out of ammonia. I
wasn't sure of the original concentration (the purpose of the lab was
for students to determine that), so I decided to approximate based on
smell. At first, I found it was too choking, so I added more water,
then I found it too tolerable, so I added more ammonia. Finally, I
felt content with the level of noxiousness and let the students
continue with the lab.