Mercury characteristics

PHYSICAL PROPERTIES | CHEMICAL PROPERTIES | APPLICATION OF MERCURY | MERCURY IN ENVIRONMENT | TOXICITY

General information

chemical symbol: Hg
metal, silver-colored
liquid in room temperature
high density
high surface tension
breaks up easily into many small droplets
dissolves some metals giving amalgams
slightly solubie in water
naturally occurring
expands and contract evenly with temperature changes
flammability class: non-combustible liquid

Physical properties

atomic mass average: 200.59
boiling point: 357oC / 675oF / 630K
electrical conductivity: 0.0104 X 106 / cm Ohm
thermal conductivity: 0.0834 W / cmK
density: 13.546 g / cm3 @ 300K
melting point: -38.72oC / -37.7oF / 234.28K
molar volume: 14.81 cm3 / mole
vapor pressure: 0.0002Pa @ -38.72oC
heat of vaporization: 59.229 kJ / mol

Chemical properties

valence states: elementar Hg0, mercurous Hg+1, mercuric Hg+2
most stable form: elementar mercury
thermally unstable both forms Hg+1, Hg+2, decompose to elemental mercury
ionic forms: Hg22+, Hg2+
inorganic mercury mainly in a form of salts, mostly week soluble in water
Application of mercury and its compounds

thermometers
manometers
barometers
mercury porosimeters
jewellery making
contact switches
alkaline batteries
fluorescent light bulbs
coating the back planes of mirrors
catalyst in the production of polymer products
dental amalgams
paints
extraction of gold and silver
calomel reference electrodes
polarography
disinfectants, fungicides and pesticides

Mercury in environment

naturally occurring element, mainly in the form of cinnabar ore (HgS)
fossil fuels and with trace amount in minerals and rocks
soil contaminated through the natural breakdown of mercury containing rock
more than 2/3 of total amount in atmosphere is a result of  human activity
human-made products and energy production sources
mercury compounds used as disinfectants, fungicides and pesticides
organic mercury compounds can be chemically synthesized
free-mercury can convert into methyl mercury in the presence of micro-organism
methyl mercury, which is fat-soluble, bio-accumulates in the tissue of fish
in soil from atmospheric depositions
in atmosphere by vaporization from water and land media
coal-fired boiler utilities and waste (medical & municipal) combustors' emission

Toxicity of mercury and its compounds

absorpsion through the lungs, skin and stomach
most toxic of all organic forms are methyl or di-methyl mercury
inorganic compounds can be irritating or corrosive to the skin, eyes, mucus membranes
swallowed compounds can cause nausea, vomiting, diarrhea and kidney damage
ACUTE HEALTH EFFECT
very high exposures to mercury vapor in air can cause acute poisoning
symptoms usually begin with cough, chest tightness and breathing difficulty
direct exposure to mercury vapor can cause discoloration of lens in the eye
CHRONIC HEALTH EFFECT
uncontrollable tremor (shaking) of the hands, tongue or eyelids
trouble balancing and walking
wide swings of mood, easily irritated, fright, depressed, excited for no apparent reason
hallucinations
memory loss
inability to concentrate
gums become soft and spongy, loosen teeth
cause birth defects in children born of exposed mothers