Calomel, they used to give it to children ...

It may be hard to believe now, but this was considered good science at one time, and was used for teething with babies. It was called Calomel, but it is Mercury.

From LOYOLA UNIVERSITY CHICAGO

Medical uses for calomel were common well into the nineteenth century. It acts as a purgative and kills bacteria (and also does irreversible damage to their human hosts). Some treatments are of historical interest. The three physicians atttending Gen. Washington's final hours administered calomel to the dying President. Lewis and Clark carried it on their expedition and used it to treat their men's STD's. Louisa May Alcott (author of Little Women) suffered from its effects. Even in the present decade several cases of mercury poisoning have been attributed to facial cremes containing calomel. Such cremes are banned in the United States because mercury is readily absorbed through the skin.

http://www.luc.edu/faculty/spavko1/minerals/calomel/calomel-main.htm

Mercurous Chloride MSDS information

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3. Hazards Identification

Emergency Overview
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WARNING! HARMFUL IF SWALLOWED, INHALED OR ABSORBED THROUGH SKIN. CAUSES IRRITATION TO SKIN, EYES AND RESPIRATORY TRACT. MAY CAUSE ALLERGIC SKIN REACTION. MERCURY COMPOUNDS AFFECT THE KIDNEYS AND CENTRAL NERVOUS SYSTEM.

J.T. Baker SAF-T-DATA^(tm) Ratings (Provided here for your convenience)
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Health Rating: 3 - Severe (Poison)
Flammability Rating: 0 - None
Reactivity Rating: 0 - None
Contact Rating: 3 - Severe (Life)
Lab Protective Equip: GOGGLES; LAB COAT; PROPER GLOVES
Storage Color Code: Blue (Health)
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Potential Health Effects
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Inhalation:
Causes irritation to the respiratory tract. Symptoms include sore throat, coughing, pain, tightness in chest, breathing difficulties, shortness of breath and headache. Pneumonitis may develop. Can be absorbed through inhalation with symptoms to parallel ingestion.
Ingestion:
Toxic! Average lethal dose for inorganic mercury salts is about 1 gram. May cause burning of the mouth and pharynx, abdominal pain, vomiting, bloody diarrhea. May be followed by a rapid and weak pulse, shallow breathing, paleness, exhaustion, tremors and collapse. Delayed death may occur from renal failure.
Skin Contact:
Causes irritaton. Symptoms include redness and pain. May cause burns. May cause sensitization. Can be absorbed through the skin with symptoms to parallel ingestion.
Eye Contact:
Causes irritation to eyes, may cause burns and eye damage.
Chronic Exposure:
Chronic exposure through any route can produce central nervous system damage. May cause muscle tremors, personality and behavior changes, memory loss, metallic taste, loosening of the teeth, digestive disorders, skin rashes, brain damage and kidney damage. Can cause skin allergies and accumulate in the body. Repeated skin contact can cause the skin to turn gray in color. Not a known reproductive hazard, but related mercury compounds can damage the developing fetus and decrease fertility in males and females.
Aggravation of Pre-existing Conditions:
Persons with nervous disorders, or impaired kidney or respiratory function, or a history of allergies or a known sensitization to mercury may be more susceptible to the effects of the substance.


Wiki page on this

Some photos and information here

PubMed article

Unregulated potions still cause mercury poisoning
		The toxicity of inorganic mercury, known as the mercuric or mercurous form, has been recognized for centuries. Roman historians noted that men working inSpanish cinnabar mines, rich in red mercuric sulfide, developed tremors, mental deterioration, and ataxia. The idea for Lewis Carroll's mad hatter inAlice in Wonderland came from his knowledge of the neural toxicity of mercuric nitrate, which was used in the fur industry to make felt. Mercurous compounds became the most common form of mercury used in medicinal preparations. They are often regarded as safe and nontoxic, reflected in the innocent names of the preparations, which suggest gentleness and beauty : sweet sublimate, mercurous dulcis, and calomel (fromcalos, meaning “good,” and melas,“black”). Calomel, or mercurous chloride, probably originated inChina and was used by Paracelsian physicians in the 16th century. It was used to treat malaria and yellow fever, and a preparation called “wormchocolate” or “worm candy” was given to patients infested with helminths.1 Toxic effects were soon noticed in individuals given large doses for long periods, in whom excessive salivation, gum inflammation, loosening of the teeth, gastrointestinal upset, and an ashen appearance developed. They had troubling neurologic symptoms, such as arm and facial tremors, hyperfine, ataxia, and erethism—unusual timidity and personality change.In 1825, a poem appeared in a Virginia publication warning physicians of the dangers of calomel : “Since Calomel's become their boast,/How many patients have they lost,/How many thousands they make ill,/Of poison, with their calomel.”2(p253) Some physicians became alarmed by the toxicity of mercury-containing medicines. 1 In1822, Samuel Thomson declared that, the practice of giving poison as medicine, which is so common among the medical faculty at the present day, is of the utmost importance to the public....and [I] enforce in the strongest manner on their minds the pernicious consequences that have happened and are daily taking place by reason of giving mercury, arsenic, and other deadly poisons to cure diseases.3 The toxic potential of calomel was highlighted in 1948. A Cincinnatipediatrician discovered that a common infantile and childhood illness called acrodynia or “pink disease” was caused by the widespread use of calomel in treating childhood teething and constipation.4 As late as 1950,acrodynia accounted for more than 3% of admissions to children's wards inLondon hospitals. Official statistics record that 585 children died of pink disease between 1939 and 1948 in England and Wales. Because of the recognition of mercury's toxicity, compounds containing mercury have been banned from almost all regulated drugs and over-the-counter preparations in the United States and many other countries. But mercury still appears in unregulated potions, as shown by Weldon and colleagues' study. The authors report a series of patients in whom elevated urinary concentrations of mercury developed, and they had symptoms suggestive of inorganic mercury poisoning, such as tremor and paresthesia. The women had used a cream containing calomel for a prolonged period, and enough mercury had become systemically absorbed to produce a marked rise in urine mercury. Women usually bought the cream in Mexico, although one fifth had obtained it in theUnited States at flea markets or health shops. Such beauty creams are available worldwide and have been associated with renal and peripheral nerve damage. Other unregulated potions containing mercury are available in the UnitedStates. Kang-Yum and Oransky report the cases of 3 patients who developed in organic mercury poisoning from Chinese herbal and patent medicines taken orally or as salves.5 Their article includes a table listing 18 different Chinese patent medicines that contain mercurials. Physicians should think of mercury intoxication in all patients with unexplained neurologic or cognitive symptoms. Patients who have had access to unregulated products, from either the United States or elsewhere, are most at risk. If the diagnosis is suspected, the patient's mercury levels should be measured and then the suspected product analyzed.

Hard to imagine.