HIO Peeps": During WW-2, I was a master horizontal bombardier and Nordan Bombsight mech. Since the Nordan bombsight was still considered secret at that time, we had to work in a closed, unventilated (no electricity there) Quonset Hut, temps ran to around 135 F. Shall I say hot and humid?
To establish a true vertical, we used open pools of mercury about 6 " in diameter to calibrate the telescope's vertical, a critical factor.
Now pools of open mercury at 135 F = close to a sat point of releasing mercury vapor.
I might also add that we filled hypodermics with the mercury and shot down flies with it ?? sheesh.
To cap it off, we used Carbontetrachloride to wash the basic parts with, 180 proof alky was used to clean the lens with - it had a horrible evaporation rate that just equalled it's trading value hehehehe
I sort a giggle when I now see that if a Mercury based thermometer is broken, you must redo the entire house. For your dental work, you may end up with a full drop of mercury in your tummy, yet

Need I remind you that a drop of mercury is used is 'all' energy saving light bulbs?
In any event, we worked for over a year under these conditions, the worst possibly imaginable, no-one knew better, yet no-one developed any adverse symptoms ?? I haven't degenerated into a drooling idiot, yet, but don't ask my wife, she is prejudiced.
It appears that form of the mercury is it's basic, danger classification. Pure liquid mercury seem to be the least harmful.
In fact, a tablespoon of mercury orally, was the standard recommendation for constipation in my US Pharm of 1849?
So use the mercury if you wish, be confident that it doesn't equal cyanide, but read and follow all of the safety instructions.
Don Jose de La Mancha el *Tropical Trampo*