# Why is mercury now seldom seen in laboratories?

Aug 10, 2015

Are you asking why we don't see mercury in barometers anymore?

#### Explanation:

Safety considerations are the obvious reasons. Mercury is (i) extremely dense (13.55 $g$ $m {L}^{-} 1$ at 300K), (ii) quite toxic, and its vapour pressure is such that it will be inhaled in very low doses, and (iii) that its liquid behaviour is quite fascinating. Given the natural curiosity of students, mercury is not a good thing to store in the lab.

As a student myself, I have floated pound coins in it, used it for electrical switches, and later (legitimately!) dissolved alkali metals in it for use in reductions. Should your container break (inevitable even with grad students), however, you've got droplets of mercury everywhere; and the metal will inhabit every pinhole and penetrate every crack. This is a major cleanup job, which contract cleaners won't touch. There are now also some good alternatives to the use of mercury for reduction.

Instruments that measure pressure by electronic means have also meant the gradual phasing out of the old mercury manometer.

Aug 10, 2015