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Mercury
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For more information,
contact David Eppstein by email at
deppstein@masco.harvard.edu,
or by calling 617-632-2860.
3.0 FORMS OF MERCURY
The following section provides an explanation and general overview
of the forms of Mercury. Mercury refers to any
of the different chemical forms that it can take including elemental
mercury (Hg 0), methyl mercury (CH3Hg+), dimethyl mercury ((CH3)2Hg)
and divalent mercury (Hg 2+).
Mercury as per the periodic chart takes the symbol "Hg".
which comes from the Latin - hydrargyrum which translated, means,
liquid silver. Mercury, together with gold and silver make up
only approximately 0.00001 percent of the earth's crust. Mercury
is obtained from cinnabar, also known as mercuric sulfide by heating
it in air. The atomic weight of the element is 80 and it's atomic
weight is 200.59.
Elemental mercury is the form of mercury which is nonionized;
familiar to most as the silvery liquid. It can volatilize to
the atmosphere at normal temperatures. Over 90 percent of mercury
in the atmosphere is mercury zero, although other forms may be
considerably higher than 10 percent near sources. Because it
does not adsorb to particulates and is not very water soluble,
it is removed from the atmosphere very slowly with a half life
in the atmosphere of about a year. The liquid or amalgam form
is not adsorbed during digestion, but the vapor is readily absorbed
by the lungs.
Mercury will not bioaccumulate unless it is converted to this
simple organic compound, CH3Hg+. Methyl mercury is water soluble.
Virtually all of the mercury in fish is methyl mercury, and it
is readily absorbed during digestion.
Dimethyl mercury is a volatile substance that boils in normal
circumstances at 96ºC (205ºF), is readily absorbed by
the biomass or skin and may be inhaled as vapor.
Mercury two is the mercuric ion. Because it is water soluble
and associates with particulates, atmospheric deposition of mercury
two is relatively fast, either as dry deposition or precipitation.
Combustion sources can emit both mercury zero and mercury two.
Mercury two can also be produced in the atmosphere by the oxidation
of mercury zero by ozone or other oxidants.
There are many common products that contain mercury such as the
thermometer. In addition, mercury is widely used in or as part
of metal amalgams, lab equipment, lab instrumentation, many forms
of electrical apparatus components, pesticides, chlorine production,
anti-fouling paint, batteries and various catalysts. The most
common salt form of mercury is mercuric chloride (HgCl2).
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