Inorganic Salts: Mercury Compounds

Study Notes

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.

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.

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.

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.

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.