3.0 FORMS OF MERCURY


3.1 Purpose

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+).

3.2 Types of Mercury

3.2.1 Mercury the Element

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.

3.2.2 Elemental Mercury (Hg 0)

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.

3.2.3 Methyl Mercury (CH3Hg+)

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.

3.2.4 Dimethyl Mercury (CH3)2Hg

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.

3.2.5 Divalent Mercury (Hg 2+)

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.

3.3 Uses of Mercury

3.3.1 Mercury Products

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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