NavList:

Bill you wrote: 2) If spilled, the mercury would corrode metal components of the aircraft, quite speedily in the case of aluminium.

Too true.  My only (thank goodness) experience of a formal RAF Board of Enquiry was over Christmas 1969-70 as Junior Member of an enquiry into serious damage to a Bristol Britannia transport aircraft.  Mercury from a damaged Fortin’s barometer had burned a hole through the aircraft.  The barometer had been wrapped in polythene sheet and formed part of a package of test equipment being flown from the UK to the USA.  When visiting the site where the package was taken from storage using a fork lift truck, I noticed a small globule of mercury in a crack between the concrete showing that the barometer had been damaged before ever reaching the aircraft.  We were able to follow the trail to the pan where the aircraft was loaded.  By the time the aircraft was routinely inspected after landing in the USA next day, further seepage of mercury though the imperfect polythene wrapping had burned a hole though the aircraft floor and into the fuselage below.  DaveP