Mercury (II) iodide

Structural formula
General
Surname	Mercury (II) iodide
other names	Mercury iodide Hydrargyrum bijodatum
Molecular formula	HgI 2
Brief description	odorless, red solid
External identifiers / databases
CAS number 7774-29-0 EC number 231-873-8 ECHA InfoCard 100,028,976 PubChem 24485 ChemSpider 22893 DrugBank DB04445 Wikidata Q414632
properties
Molar mass	454.45 g mol −1
Physical state	firmly
density	6.271 g cm −3
Melting point	259 ° C
boiling point	354 ° C
Vapor pressure	0.006 h Pa (80 ° C)
solubility	almost insoluble in water (0.06 g l −1 at 25 ° C) very soluble in DMSO (1000 g l −1 at 25 ° C) soluble in hot ethanol sparingly soluble in cold ethanol and diethyl ether
safety instructions
GHS hazard labeling from  Regulation (EC) No. 1272/2008 (CLP) , expanded if necessary danger H and P phrases H: 330-310-300-373-410 P: 273-280-302 + 352-304 + 340-308 + 310
MAK	0.1 mg m −3
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Mercury (II) iodide is a chemical compound and one of the halides of the heavy metal mercury . Direct contact should be avoided because of its high toxicity. Mercury (II) iodide is a semiconductor and sensitive to light. With potassium iodide and mercury (II) chloride it forms crystallizable double compounds .

Occurrence

Mercury (II) iodide occurs only rarely in nature in the form of the mineral coccinite .

Extraction and presentation

Mercury (II) iodide can be represented directly from the elements mercury and iodine :

${\displaystyle \mathrm {Hg+\ I_{2}\longrightarrow \ HgI_{2}} }$

Even with the addition of mercury (II) chloride to an aqueous solution of potassium iodide it arises as a red precipitate:

${\displaystyle \mathrm {HgCl_{2}+\ 2\ KI\longrightarrow \ HgI_{2}+2\ KCl} }$

properties

Mercury (II) iodide in the yellow β- (left) and the red α-phase (right).

Mercury (II) iodide is a scarlet, heavy, microcrystalline powder that turns yellow when heated to its melting point at 259 ° C. It is toxic to most living organisms and behaves similarly to mercury (II) chloride . For salt-like compounds, mercury (II) iodide has a very low boiling point of 354 ° C.

use

If mercury (II) iodide, which is sparingly soluble in water, is dissolved in an excess of potassium iodide solution , the complex compound potassium tetraiodomercurate (II) , which is used in the Nessler reaction, is obtained. It is also used in veterinary medicine as a tincture for injuries.

Individual evidence

1. ↑ ^{a b c d e f g h} Entry on mercury (II) iodide in the GESTIS substance database of the IFA , accessed on February 1, 2016(JavaScript required) .
2. ↑ Data sheet Mercury (II) iodide (PDF) from Merck , accessed on June 15, 2017.
3. ↑ Dimethyl Sulfoxide (DMSO) Solubility Data. Gaylord Chemical Company, LLC; Bulletin 102, June 2014, p. 14. (PDF)
4. ^ ^{A b} Dale Perry: Handbook of Inorganic Compounds, Second Edition . CRC Press, 2016, ISBN 978-1-4398-1462-8 , pp. 482 ( books.google.de ).
5. ↑ Not explicitly listed in Regulation (EC) No. 1272/2008 (CLP) , but with the specified labeling falls under the group entry inorganic compounds of mercury with the exception of mercuric sulphide and those specified elsewhere in this Annex in the Classification and Labeling Inventory of European Chemicals Agency (ECHA), accessed on February 1, 2016. Manufacturers or distributors can expand the harmonized classification and labeling .
6. ↑ H. Hager, F. v. Bruchhausen, P. Surmann, E. Nürnberg: Hagers Handbook of Pharmaceutical Practice , Springer Verlag, 1999, ISBN 3-540-52641-2 , p. 473.
7. ↑ The Yellow polymorph of Mercuric Iodide (HgI2) . In: Helvetica Chimica Acta . tape 86 , no. 5 , May 1, 2003, p. 1410-1422 , doi : 10.1002 / hlca.200390126 .
8. ^ AF Holleman , E. Wiberg : Textbook of Inorganic Chemistry . 57-70 Edition. Walter de Gruyter, Berlin 1964, p. 493.