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| Names | |
|---|---|
| IUPAC name Mercury(II) oxide | |
| Other names | |
| Identifiers | |
3D model (JSmol) | |
| ChemSpider |
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| ECHA InfoCard | 100.040.580 |
| KEGG |
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| RTECS number |
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| UNII | |
| UN number | 1641 |
| |
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| Properties | |
| HgO | |
| Molar mass | 216.591 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 inalcohol,ether,acetone,ammonia |
| Band gap | 2.2 eV[1] |
| −44.0·10−6 cm3/mol | |
Refractive index (nD) | 2.5 (550 nm)[1] |
| Thermochemistry | |
Std molar entropy(S⦵298) | 70 J·mol−1·K−1[2] |
Std enthalpy of formation(ΔfH⦵298) | −90 kJ·mol−1[2] |
| Hazards | |
| Occupational safety and health (OHS/OSH): | |
Main hazards | Extremely toxic, environmental pollutant |
| GHS labelling:[4] | |
   | |
| Danger | |
| H300+H310+H330,H372,H410 | |
| P260,P262,P264,P270,P271,P273,P280,P284,P301+P316,P302+P352,P304+P340,P316,P320,P321,P330,P361+P364,P391,P403+P233,P405,P501 | |
| NFPA 704 (fire diamond) | |
| Flash point | Non-flammable |
| Lethal dose or concentration (LD, LC): | |
LD50 (median dose) | 18 mg/kg (oral, rat)[3] |
| Safety data sheet (SDS) | ICSC 0981 |
| Related compounds | |
Otheranions | Mercury sulfide Mercury selenide Mercury telluride |
Othercations | Zinc oxide Cadmium oxide |
Related compounds | Mercury(I) oxide |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Mercury(II) oxide, also calledmercuric oxide or simplymercury oxide, is theinorganic compound with the formulaHgO. It has a red or orange color. Mercury(II) oxide is a solid at room temperature and pressure. The mineral formmontroydite is very rarely found.
An experiment for the preparation of mercuric oxide was first described by 11th century Arab-Spanish alchemist,Maslama al-Majriti, inRutbat al-hakim.[6] It was historically called red precipitate (as opposed to white precipitate,mercuric amidochloride).
In 1774,Joseph Priestley discovered that oxygen was released by heating mercuric oxide, although he did not identify the gas asoxygen (rather, Priestley called it "dephlogisticated air," as that was theparadigm that he was working under at the time).[7]
The red form of HgO can be made by heating Hg in oxygen at roughly 350 °C, or bypyrolysis ofHg(NO3)2.[8] The yellow form can be obtained by precipitation of aqueous Hg2+ with alkali.[8] 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°.[8]
HgO is soluble in many conventional strong acids through protonation of the anion.[9] The exceptions include acids which form insoluble mercury(II) salts, likemercury(II) iodide in the case ofhydroiodic acid. Dissolution is also possible through complexation of the cation; e.g. cyanide ligands form stable water soluble mercury(II) complexes.
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 mineralcinnabar (hexagonal,hP6, P3221); both are characterized by Hg-O chains.[10] At pressures above 10 GPa both structures convert to atetragonal form.[1]
Mercury oxide is sometimes used in the production of mercury as it decomposes quite easily. When it decomposes, oxygen gas is generated.[citation needed]
It is also used as a material forcathodes inmercury batteries.[11]
Mercury oxide is a highly 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 theEU.[12]
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.[13]
{{cite book}}:ISBN / Date incompatibility (help)Mercury(II) oxide anode mercury battery.
