Mercury(II) oxide

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Mercury(II) oxide
Mercury(II) oxide
Mercury(II) oxide
Names
IUPAC name
Mercury(II) oxide
Other names
Mercuric oxide
Montroydite
Red mercury
Identifiers
21908-53-2 YesY
ChemSpider 28626 YesY
Jmol 3D model Interactive image
KEGG C18670 YesY
PubChem 30856
RTECS number OW8750000
UN number 1641
  • InChI=1S/Hg.O YesY
    Key: UKWHYYKOEPRTIC-UHFFFAOYSA-N YesY
  • [Hg]=O
Properties
HgO
Molar mass 216.59 g·mol−1
Appearance Yellow or red solid
Odor odorless
Density 11.14 g/cm3
Melting point 500 °C (932 °F; 773 K) (decomposes)
0.0053 g/100 mL (25 °C)
0.0395 g/100 mL (100 °C)
Solubility insoluble in alcohol, ether, acetone, ammonia
Band gap 2.2 eV[1]
2.5 (550 nm)[1]
Structure
orthorhombic
Thermochemistry
70 J·mol−1·K−1[2]
−90 kJ·mol−1[2]
Vapor pressure {{{value}}}
Related compounds
Other anions
Mercury sulfide
Mercury selenide
Mercury telluride
Other cations
Zinc oxide
Cadmium oxide
Related compounds
Mercury(I) oxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YesYN ?)
Infobox references

Mercury(II) oxide, also called mercuric oxide or simply mercury oxide, has a formula of HgO. It has a red or orange color. Mercury(II) oxide is a solid at room temperature and pressure. The mineral form montroydite is very rarely found.

History

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In 1774, Joseph Priestley discovered that oxygen was released by heating mercuric oxide, although he did not identify the gas as Oxygen (rather, Priestley called it "dephlogisticated air", as that was the paradigm that he was working under at the time.)[3]

Synthesis

Montroydite structure (red atoms are oxygens)
Cinnabar structure

The red form of HgO can be made by heating Hg in oxygen at roughly 350 °C, or by pyrolysis of Hg(NO3)2.[4] The yellow form can be obtained by precipitation of aqueous Hg2+ with alkali.[4] The difference in color is due to particle size, both forms have the same structure consisting of near linear O-Hg-O units linked in zigzag chains with an Hg-O-Hg angle of 108°.[4]

Structure

Under atmospheric pressure mercuric oxide has two crystalline forms: one is called montroydite (orthorhombic, 2/m 2/m 2/m, Pnma), and the second is analogous to the sulfide mineral cinnabar (hexagonal, hP6, P3221); both are characterized by Hg-O chains.[5] At pressures above 10 GPa both of those structures convert to a tetragonal form.[1]

Uses

HgO is sometimes used in the production of mercury as it decomposes quite easily. When it decomposes, oxygen gas is generated.

It is also used as a material for cathodes for mercury batteries.[6]

Health issues

The label on an HgO powder bottle.

Mercury oxide is a toxic substance which can be absorbed into the body by inhalation of its aerosol, through the skin and by ingestion. The substance is irritating to the eyes, the skin and the respiratory tract and may have effects on the kidneys, resulting in kidney impairment. In the food chain important to humans, bioaccumulation takes place, specifically in aquatic organisms. The substance is banned as a pesticide in the EU.[7]

Evaporation at 20 °C is negligible. HgO decomposes on exposure to light or on heating above 500 °C. Heating produces highly toxic mercury fumes and oxygen, which increases the fire hazard. Mercury(II) oxide reacts violently with reducing agents, chlorine, hydrogen peroxide, magnesium (when heated), disulfur dichloride and hydrogen trisulfide. Shock-sensitive compounds are formed with metals and elements such as sulfur and phosphorus.[8]

References

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External links