Potassium tetraiodomercurate (II)

Structural formula
General
Surname	Potassium tetraiodomercurate (II)
other names	Potassium tetraiodomercurate Mayer's reagent Nessler's reagent Potassium mercury iodide Mercury Potassium Iodide Thoulet's solution
Molecular formula	K 2 [HgI 4 ]
Brief description	light yellow solid
External identifiers / databases
CAS number 7783-33-7 17442-06-7 (Thoulet's solution) EC number 231-990-4 ECHA InfoCard 100,029,082 PubChem 24542 Wikidata Q416649
properties
Molar mass	786.48 g mol −1
Physical state	firmly
density	4.29 g cm −3
solubility	soluble in water
safety instructions
GHS labeling of hazardous substances danger H and P phrases H: 300-310-330-373-410 P: 260-273-280-301 + 310-302 + 350-304 + 340-310-361
MAK	0.02 mg m −3
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Potassium tetraiodomercurate (II) is a chemical compound from the group of potassium compounds , iodine complexes and mercury compounds .

Extraction and presentation

Potassium tetraiodomercurate (II) can be obtained by reacting mercury (II) chloride or mercury (II) iodide with potassium iodide .

${\displaystyle \mathrm {HgCl_{2}+4\ KI\longrightarrow K_{2}[HgI_{4}]+2\ KCl} }$

${\displaystyle \mathrm {HgI_{2}+2\ KI\longrightarrow K_{2}[HgI_{4}]} }$

use

Potassium tetraiodomercurate (also known as Neßler's reagent A, after Julius Neßler , who described the solution in his dissertation in 1856) is used in the form of a solution for nitrogen determination. In this Neßler reaction , potassium tetraiodomercurate and ammonia form a red-brown color complex [Hg ₂ N] I, the iodide of the cation of Millon's base . The detection is very sensitive to ammonium / ammonia and is used in water analysis for its quantitative determination. The disadvantage is the cross-sensitivity to simple amines , which occur in abundance in strongly revitalized water (e.g. fish ponds, waste water).

The aqueous solution of potassium tetraiodomercurate (from 1 part of mercury (II) iodide and 1.24 parts of potassium iodide with a maximum density of 3.196 g / cm³) is also known as Thoulets solution. The solution, named after the French mineralogist Julien Olivier Thoulet (1843–1936), can be used as a heavy liquid to determine the density of minerals and to separate mineral mixtures.

Individual evidence

1. ^ Huey Rong C. Jaw, Margaret M. Mooney, Thomas Novinson, William C. Kaska, Jeffrey I. Zink: Optical properties of the thermochromic compounds disilver tetraiodomercurate ^{(2 -)} and dicopper tetraiodomercurate ^(2–) . In: Inorganic Chemistry . tape 26 , no. 9 , 1987, pp. 1387-1391 , doi : 10.1021 / ic00256a011 .
2. ↑ ^{a b c d e} Entry on potassium tetraiodomercurate (II) in the GESTIS substance database of the IFA , accessed on January 8, 2020(JavaScript required) .
3. ↑ Entry on Mayer's reagent. In: Römpp Online . Georg Thieme Verlag, accessed on August 24, 2017.
4. ^ AF Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 102nd edition. Walter de Gruyter, Berlin 2007, ISBN 978-3-11-017770-1 , p. 1506.
5. ↑ Julius Neßler: About the behavior of iodine mercury and mercury compounds in general to ammonia and about a new reaction to ammonia . Poppen, Freiburg im Breisgau 1856, urn : nbn: de: bvb: 12-bsb10853243-4 (dissertation, University of Freiburg).
6. ↑ Data sheet potassium tetraiodomercurate (II) (PDF) from Merck , accessed on March 2, 2010.
7. ↑ Entry on Neßler's reagent. In: Römpp Online . Georg Thieme Verlag, accessed on August 24, 2017.
8. ↑ entry to Thoulets solution. In: Römpp Online . Georg Thieme Verlag, accessed on July 23, 2015.