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Oxidation States of Mercury

Mercury occurs in three oxidation states:

• Elemental Mercury or Hg⁰
• Monovalent Mercury or Hg+ or Hg¹
• Mercurous
• Divalent Mercury or Hg⁺⁺ or Hg²⁺
• Mercuric

Mercury binds in two states Hg⁺ (mercurous) and Hg⁺⁺ (mercuric) to form mercury compounds that can be either organic or inorganic mercury compounds.

The distinction between Elemental Mercury, Inorganic Mercury and Organic Mercury is much more important than the oxidation states in determining toxicity. Organic mercury compounds are most toxic.

Examples:

• Elemental Mercury
• A form of inorganic mercury
• Volatile at room temperature
• Inorganic Mercury (Mercury Salts)
• Formed when mercury combines with elements other than carbon, such as chlorine, sulfur, or oxygen
• Mercuric chloride, mercuric sulfide, mercurous chloride
• Organic Mercury
• Formed when mercury combines with carbon
• Volatile at room temperature
• Methylmercury, mercuric acetate, methylmercuric chloride, dimethyl mercury, and phenylmercuric acetate

The routes of entry into the body associated with mercury are:

• Inhalation (breathing)
• Absorption (touching with bare skin)
• Ingestion

Elemental Mercury emits vapor readily at room temperature.

Elemental Mercury vapor is colorless, odorless & tasteless.

Elemental Mercury is highly toxic, especially to children, a developing fetus, and the elderly.

When mercury is spilled, microscopic "beads" may be left behind after cleaning and each "bead" will continue to emit vapor.

There are suitable alternatives to mercury and mercury containing devices for virtually everything that contains mercury.
Spilled Mercury on Floor

When mercury spills onto floors and other surfaces, it fractures into hundreds, even thousands of tiny beads; many are invisible to the naked eye, yet still emitting vapor.