Mercury(II) oxide

Mercury(II) oxide

Names
IUPAC name Mercury(II) oxide
Other names Mercuric oxide Montroydite Red mercuric oxide Red mercury
Properties
Chemical formula	HgO
Molar mass	216.59 g/mol
Appearance	Yellow or red solid
Odor	Odorless
Density	11.14 g/cm3
Melting point	500 °C (932 °F; 773 K) (decomposes)
Boiling point	Decomposes
Solubility in water	0.0053 g/100 ml (25 °C) 0.0395 g/100 ml (100 °C)
Solubility	Reacts with acids Insoluble in acetone, alcohols, ammonia, ethers,
Vapor pressure	~0 mmHg
Thermochemistry
Std molar entropy (So298)	70 J·mol−1·K−1
Std enthalpy of formation (ΔfHo298)	−90 kJ/mol
Hazards
Safety data sheet	Sigma-Aldrich
Lethal dose or concentration (LD, LC):
LD50 (Median dose)	18 mg/kg (rat, oral)
Related compounds
Related compounds	Zinc oxide Cadmium oxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Mercury(II) oxide, or mercuric oxide is a red or orange solid, with the formula HgO.

Properties

Chemical

Mercury(II) oxide reacts with most acids to give mercury salts, making it the basic precursor for any mercury compound.

Physical

Mercury(II) oxide is a dense red or orange solid, insoluble in water and organic solvents.

Availability

Mercuric oxide can be found in the cathode of old mercury batteries.

Mercury oxide can be bought from chemical suppliers, though it's not easy to get hold of.

Mercury and mercury compounds cannot be freely acquired in EU.

Preparation

Mercuric oxide can be made via pyrolysis of mercury(II) nitrate at temperature above 360 °C, but below 500 °C.

Hg(NO₃)₂ → HgO + 2 NO₂ + ½ O₂

An less hazardous route involves hydrolyzing mercury(II) sulfate in water using sodium hydroxide in a 1:2 molar ratio:

HgSO₄ + 2 NaOH → HgO + Na₂SO₄ + H₂O

However, the HgO obtained through this route is difficult to purify, as it's difficult to dry and contains lots of unreacted mercuric sulfate.

Projects

• Make mercury(II) chloride
• Make elemental mercury

Handling

Safety

Mercury(II) oxide is extremely toxic. Ingestion may be fatal.

Storage

In closed glass or plastic bottles, away from acids.

Disposal

Mercury(II) oxide should be converted to an insoluble mercury compound, such as mercury sulfide, then taken to hazardous waste disposal centers.

References

Relevant Sciencemadness threads

• Mercuric oxide from mercuric sulfate
• Mercury Oxide?
• Mercury Oxides