Formula HgBr2 Density 6.03 g/cm³ Boiling point 322 °C | Molar mass 360.41 g/mol Melting point 236 °C Appearance white solid | |
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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.
Contents
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. Also, Mercury(II) bromide can be created by reacting mercury with bromine.
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 + 3HBrThe 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.