Calomel

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Mahogany medicine chest, England, 1801-1900 Wellcome L0057102

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Packet of mercurous chloride tablets, Kassel, Germany, 1914- Wellcome L0058828

Calomel-bem-10c

Calomel is a chemical compound with the formula Hg2Cl2. Known also by its IUPAC name mercury(I) chloride, calomel is a white or colorless crystalline solid at room temperature. It has historically been used for various medical and scientific purposes, although its use has declined due to concerns over toxicity and environmental impact.

Properties and Structure

Calomel is a compound of mercury and chlorine, where mercury is in the +1 oxidation state. It is poorly soluble in water, which limits its bioavailability but has been an attribute exploited in certain medical applications. The structure of calomel consists of a linear arrangement of atoms, with mercury atoms bonded to each other and each mercury atom also bonded to a chlorine atom.

Historical Uses

Historically, calomel was used in medicine, primarily as a purgative or diuretic. It was believed to cleanse the body of impurities and was used in the treatment of syphilis, yellow fever, and other conditions. However, its use has been largely discontinued due to the recognition of mercury's toxicity and the development of safer and more effective treatments.

In addition to its medical applications, calomel has been used in the production of chlorine gas and as a standard in electrochemistry due to its stable electrochemical properties.

Health and Environmental Concerns

The use of calomel has raised significant health and environmental concerns. Mercury compounds, including calomel, are highly toxic and can cause mercury poisoning if ingested, inhaled, or absorbed through the skin. Symptoms of mercury poisoning include neurological damage, kidney failure, and death in severe cases.

Environmental concerns also arise from the use of calomel and other mercury compounds. Mercury can accumulate in water bodies, leading to contamination of fish and other aquatic life. This bioaccumulation poses a risk to wildlife and humans who consume contaminated fish.

Current Status

Today, the use of calomel in medicine has been largely phased out in favor of safer alternatives. However, it may still be found in some laboratories and industrial processes. The handling of calomel requires strict safety precautions to prevent exposure to mercury.

See Also

• Mercury poisoning
• Chlorine
• Electrochemistry