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Calomel is a powder that is white when pure, and it has been used as a pigment in painting in 17th century South Americas art and in European medieval manuscripts. [14] When it is exposed to light or contains impurities it takes on a darker tint. [7] Calomel is made up of mercury and chlorine with the chemical formula Hg 2 Cl 2. Depending on ...
The name calomel is thought to come from the Greek καλός "beautiful", and μέλας "black"; or καλός and μέλι "honey" from its sweet taste. [4] The "black" name (somewhat surprising for a white compound) is probably due to its characteristic disproportionation reaction with ammonia, which gives a spectacular black coloration due to the finely dispersed metallic mercury formed.
The saturated calomel electrode (SCE) is a reference electrode based on the reaction between elemental mercury and mercury(I) chloride. It has been widely replaced by the silver chloride electrode , however the calomel electrode has a reputation of being more robust.
On May 4, there was some hope following a high dose of calomel (toxic mercury chloride) administered by his English physician Archibald Arnott and two of his colleagues, but against the advice of Corsican physician François Antommarchi. The effect, however, was extremely violent. [5] During the night of May 4-5, Napoleon was in a comatose state.
Inorganic mercury compounds, such as mercury(I)chloride (), were found to have diuretic properties when they were used to treat syphilis. [2] Proposed use of these compounds date back at least to the 16th century, shortly after the beginning of the syphilis epidemic in 1497 following Columbus' return to Europe.
Potentiometric titrations were first used for redox titrations by Crotogino. He titrated halide ions with potassium permanganate using a shiny platinum electrode and a calomel electrode. He said that if an oxidizing agent is added to a reducing solution then the equilibrium between the reducing substance and reaction product will shift towards ...
It arises from the reaction of mercury(II) chloride and ammonia (Calomel reaction), where the resulting mercuric amidochloride is highly insoluble. It forms white crystals in the shape of small prisms. It tastes earthy and metallic, but is a deadly poison and should not be ingested. [2]
Commercial reference electrodes consist of a glass or plastic tube electrode body. The electrode consists of a metallic silver wire (Ag (s)) coated with a thin layer of silver chloride (AgCl), either physically by dipping the wire in molten silver chloride, chemically by electroplating the wire in concentrated hydrochloric acid (HCl) [3] or electrochemically by oxidising the silver at an anode ...