Red Iodide of Mercury

Hydraryri Biniodidum (rubrum) [red iodide of mercury] from one-sixteenth to one-eighth of a grain. 

Dissolve the perchloride of mercury in three pints, and the iodide of potassium in the remainder, of the water, and mix the solutions. When the temperature has fallen to that of the atmosphere, decant the supernatant liquor from the precipitate (red iodide of mercury), and, having collected the latter on a filter, wash it twice with cold distilled water, and dry it at a temperature not exceeding 212 F. 

Red precipitate of mercury (I) chromate Green precipitate of mercury (I) iodide White precipitate of mercury (I) sulfate Amalgamation occurs... 

Potassium iodide when added slowly to the solution red precipitate of mercury(II) iodide ... 

A single chemical substance, simple or compound, exists at once in two different solid forms, such as the yellow iodide of mercury with the red iodide. 

Hydrargyri Chloridum Corrosivum (corrosive sublimate) Like all the mercurials, mercuric chloride (HgCl2) was regarded as an alterative. A biliary stimulant and cathartic used in a wide range of ailments (see Chapter 7). It was also supplied as yellow iodide of mercury, red oxide of mercury, and in pill and ointment. Not quite the same as calomel (Hydrargyi Chloridum Mite or mercurous chloride [HgCI]). Because it was much harsher than calomel, corrosive sublimate was used far more judiciously by medical staff. 

CHEMICAL PROPERTIES mercury salts yield metallic mercury when heated with sodium earbonate mereury salts may be redueed to metal by hydrogen peroxide in presenee of alkali hydroxide soluble ionized mereurie salts give a yellow precipitate or mereuric oxide with sodium hydroxide and a red precipitate of mercury diiodide with alkali iodide mercurous salts give a black precipitate with alkali hydroxides and a white precipitate of mercurous chloride (calomel) with hydrogen ehloride or soluble chlorides decomposes slowly on exposure to sunlight. 

Borgford, and J. B. Ealy, "Name That Precipitate," Chemical Demonstrations, A Sourcebook for Teachers, Vol. 2 (American Chemical Society, Washington, DC, 1988), pp. 121-123. Blue, brown, red, white, and yellow precipitates are formed when solutions containing +2 cations of mercury, nickel, lead, and barium are mixed with solutions containing carbonate, chloride, iodide, and sulfate anions. Students are asked to name and determine the formula of each precipitate and to write an ionic equation for each reaction. 

SAFETY PROFILE Similar in toxicity to bromides. Prolonged absorption of iodides may produce iodism, which is manifested by skin rash, mnning nose, headache, and irritation of mucous membranes. In severe cases, the skin may show pimples, boils, redness, black-and-blue spots, hives, and blisters. Weakness, anemia, loss of weight, and general depression may occur. Generally very soluble in water and easily absorbed into the body. The iodides of copper(I), lead(II), silver(I), and mercury(II) are poorly soluble in water. When heated to decomposition they can emit highly toxic fumes of r and iodine compounds. See also IODINE. 

It is known that when the temperature is lowered to about 126 , yellow mercury iodide changes over to the red iodide similarly, by a lowering of temperature, the mixed crystals of merciuy iodide and of mercury bromide, which are isomorphous with the yellow iodide and which play here the rdle of the a crystals, are transformed into mixed isomorphous crystals of red iodide, playing the rdle of the P crystals. 

Reinders has drawn for these crystals the curves F and t which are indicated in Fig. 87. These two curves unite for in a point whose ordinate is equal to the temperature of transformation of yellow mercury iodide into the red iodide, that is, at 126 . These two curves do not extend to the line OT where X=0 indeed, beyond a certain content in mercury bromide, one observes only the mixed a crystals. 

Actim of Mercury upm Iodide of Me l in preseme of Light. When iodide of methyl is exposed to sunlight in contact with metallic mercury, it soon bc mes coloured red from the separation of firce iodine ... 

For a red use chloride of mercury and develop with iodide of potassium. 

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