The letters “Hg” stand for mercury, also known as quicksilver or hydrargyrum, a chemical element identified with the symbol “Hg” (a Latin and Greek hybrid: hydrargyrum, from “hydr-” meaning watery or runny and “argyros” meaning silver). The atomic number for mercury is 80.
An extremely toxic chemical, Mercury was historically a medicinal panacea, used for centuries to cure a simple scrape on the knee all the way up to syphilis.
Medicinal uses for Mercury trace back as far as 1500 BC. In ancient China and Tibet, it was believed that mercury could prolong life, heal fractures, and maintain generally good health. The ancient Greeks used mercury in ointments; the ancient Egyptians and the Romans used the compound in cosmetics, although this led to deformations in the face.
Mercury was prescribed in either a pill or liquid form throughout the 19th century to treat various conditions, including constipation, depression, and toothaches, as well as to assist in child-bearing. In the beginning of the 20th century, doctors prescribed mercury to children on an annual basis as both laxative and dewormer. Mercury was also used in teething powders for infants.
The photo at the right shows the side effects when one physician treated his patient’s cold with “calomel,” a Mercury-based potion thought to make patients salivate and flush the body of “bad humors.” The toxic nature of mercury was simply unknown at the time.
Typically, mercury can be inhaled and absorbed through the skin, and exposure overall is very dangerous. Some side effects from Mercury exposure include tremors, chest pain, dyspnea, cough, violent muscular spasms, loss of memory, psychotic reactions, hallucinations, and suicidal tendencies.
Today, Mercury is still used in thermometers, barometers, manometers sphygmomanometers, float valves, some electrical switches, and other scientific apparati, although concerns about the element’s toxicity have led to the phasing out of many such devices. To replace Hg, alcohol-filled, digital, or thermistor-based instruments have found favor in clinical settings.