A ruling by the European Union heralds the demise of
those useful clinical instruments, the mercury thermometer
and the mercury sphygmomanometer. The
new laws have been passed because of worries about
mercury poisoning. Yet you can drink metallic mercury
and come to no harm. What does it all mean? There are
three forms of mercury from a toxicological point of
view: inorganic mercury salts; organic mercury compounds;
and metallic mercury. Inorganic mercury salts
are water soluble, irritate the gut, and cause severe kidney
damage. Organic mercury compounds, which are
fat soluble, can cross the blood brain barrier and cause
neurological damage. Mercury metal poses two dangers.
It can be vaporised: the vapour pressure at room
temperature is about 100 times the safe amount