Mercury(I) iodide
Encyclopedia
Mercury iodide is a chemical compound
Chemical compound
A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...

 of mercury
Mercury (element)
Mercury is a chemical element with the symbol Hg and atomic number 80. It is also known as quicksilver or hydrargyrum...

 and iodine
Iodine
Iodine is a chemical element with the symbol I and atomic number 53. The name is pronounced , , or . The name is from the , meaning violet or purple, due to the color of elemental iodine vapor....

. The chemical formula is Hg2I2. It is photosensitive and decomposes easily to mercury and HgI2.

Synthesis

Mercury(I) iodide can be prepared by direct combination of mercury
Mercury (element)
Mercury is a chemical element with the symbol Hg and atomic number 80. It is also known as quicksilver or hydrargyrum...

 and iodine
Iodine
Iodine is a chemical element with the symbol I and atomic number 53. The name is pronounced , , or . The name is from the , meaning violet or purple, due to the color of elemental iodine vapor....

:

2 Hg + I2 → Hg2I2

Structure

In common with other Hg(I) (mercurous) compounds which contain linear X-Hg-Hg-X units, Hg2I2 contains linear IHg2I units with an Hg-Hg bond length of 272 pm (Hg-Hg in the metal is 300 pm) and an Hg-I bond length of 268 pm. The overall coordination of each Hg atom is octahedral as it has in addition to the two nearest neighbours there are four other I atoms at 351 pm. The compound is often formulated as Hg22+ 2I.

Uses

Mercury(I) iodide, called Protiodide
Protiodide
Protiodide is an iodide of mercury and was a very commonly used drug in the 19th century, prescribed for everything from acne to kidney disease. It was also the treatment of choice for syphilis...

, was used as a medicine in early years. However, due to the high toxicity of the substance, it is no longer used.
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
x
OK