Mercury(II) bromide

Mercury(II) bromide

Names
IUPAC name Mercury(II) bromide
Other names Mercuric bromide
Identifiers
CAS Number	7789-47-1 N
PubChem	24612
RTECS number	OV7415000
Properties
Chemical formula	HgBr2
Molar mass	360.41 g/mol
Appearance	white solid
Density	6.03 g/cm3, solid
Melting point	237 °C (459 °F; 510 K)
Boiling point	322 °C (612 °F; 595 K)
Solubility in water	soluble
Solubility	very slightly soluble in ether
Structure
Coordination geometry	rhombic
Vapor pressure	{{{value}}}
Related compounds
Other anions	Mercury(II) fluoride Mercury(II) chloride Mercury(II) iodide
Other cations	Zinc bromide Cadmium bromide Mercury(I) bromide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Mercury(II) bromide or mercuric bromide is the chemical compound composed of mercury and bromine with the formula HgBr₂. This white crystalline solid is a laboratory reagent. Like mercury(II) chloride, it is extremely toxic.

Preparation

Mercury(II) bromide can be manufactured by: adding potassium bromide to a solution of mercuric salt and crystallizing; by precipitation using a mercury(II) nitrate and sodium bromide solution; by dissolving mercury(II) oxide in hydrobromic acid.

Reactions

Mercury(II) bromide is used as a reagent in the Koenigs–Knorr reaction, which forms glycoside linkages on carbohydrates.

It is also used to test for the presence of arsenic, as recommended by the Pharmacopoeia. The arsenic in the sample is first converted to arsine gas by treatment with hydrogen. Arsine reacts with mercury(II) bromide:

AsH₃ + 3HgBr₂ → As(HgBr)₃ + 3HBr

The white mercury(II) bromide will turn yellow, brown, or black if arsenic is present in the sample.

Mercury(II) bromide reacts violently with elemental indium at high temperatures and, when exposed to potassium, can form shock-sensitive explosive mixtures.