Inorganic Salts: Mercury Compounds

Inorganic Salts of Mercury

• Mercuric chloride (corrosive sublimate): colorless, odorless, prismatic crystals or white crystalline powder with a nauseous metallic taste; most toxic salt and common cause of acute poisoning.
• Mercurous chloride (calomel): heavy, amorphous, white, and tasteless powder.
• Mercuric sulphide (cinnabar or vermilion): red crystalline powder, not absorbed through skin and non-poisonous.
• Mercuric cyanide, oxide, and iodide: scarlet red powder.

Organic Salts of Mercury

• Methyl mercury, dimethyl mercury, ethyl mercury, and phenyl mercury.

Uses of Mercury

• Medicine: disinfectant, dental amalgam, purgative, and diuretic.
• Industry: manufacture of thermometer, barometer, calibration instruments, fluorescent and mercury vapor lamp, electrical equipment, explosives, and fireworks.
• Miscellaneous: electroplating, photography, insecticide, germicide, and constituent of fingerprint powder, paints, and embalming fluid.

Action of Mercury

• Binds with sulfhydryl groups, resulting in enzyme inhibition and pathological alteration of cellular membranes.
• Toxic to the CNS; metallic mercury vapor is a pulmonary irritant.
• Inorganic mercury salts are corrosive to the skin, eyes, and GIT, and nephrotoxic.
• Inorganic and organic forms may cause contact dermatitis.

Absorption and Excretion

• Absorbed through the GIT and respiratory tract.
• Deposited in all tissues, particularly in the liver, kidneys, spleen, and bones.
• Excreted mainly through the kidneys, liver (bile), and colonic mucous membrane.
• Passes rapidly to the fetus through placental circulation.

Signs and Symptoms of Acute Poisoning

• Inhalation of mercury vapor: chemical pneumonitis, pulmonary edema, gingivostomatitis, and CNS symptoms.
• Ingestion of inorganic mercuric salts:
  • First phase: GIT symptoms, including metallic taste, feeling of constriction in the throat, and hot burning pain.
  • First phase: kidney symptoms, including oliguria, albuminuria, and hematuria.
  • First phase: CVS symptoms, including hypertension, tachycardia, difficulty in breathing, and circulatory collapse.
  • Second phase: Glossitis, ulcerative gingivitis, renal tubular necrosis, polyuria, albuminuria, cylindruria, uremia, and acidosis.
• Fatal dose: 1-4 g of mercuric chloride, 10-60 mg/kg of methyl mercury, and 10 mg/m³ of mercury vapor.
• Fatal period: 3-5 days.
• Diagnosis: Blood mercury level > 3.6 µg/dl, and 24-h urinary excretion of mercury > 15 µg/l indicates toxicity.
• Urine and blood mercury levels are assessed by atomic absorption spectrophotometer.
• Mercury concentration of hair is best assessed by neutron activation analysis.