Zinc oxide
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| Names | |
|---|---|
| IUPAC name
Zinc oxide
| |
| Other names
Amalox
Calamine Chinese white Flowers of zinc Oxozinc Permanent white Philosopher's wool Zinc white | |
| Properties | |
| ZnO | |
| Molar mass | 81.38 g/mol |
| Appearance | White solid |
| Odor | Odorless |
| Density | 5.606 g/cm3 |
| Melting point | 1,975 °C (3,587 °F; 2,248 K) (decomposes) |
| Boiling point | Decomposes |
| 0.00042 g/100 ml (18 °C) (slowly hydrolyzes) | |
| Solubility | Reacts with acids and alkalis Insoluble in alcohols, esters, ethers, halocarbons |
| Vapor pressure | ~0 mmHg |
| Thermochemistry | |
| Std molar
entropy (S |
43.9 J·K−1·mol−1 |
| Std enthalpy of
formation (ΔfH |
-348.0 kJ/mol |
| Hazards | |
| Safety data sheet | Sigma-Aldrich |
| Flash point | Non-flammable |
| Lethal dose or concentration (LD, LC): | |
| LD50 (Median dose)
|
240 mg/kg (rat, intraperitoneal) 7,950 mg/kg (rat, oral) |
| LC50 (Median concentration)
|
2,500 mg/kg (mouse) |
| Related compounds | |
| Related compounds
|
Cadmium oxide Mercury(II) oxide |
| Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
| Infobox references | |
Zinc oxide is a white oxide of zinc used an additive in many products. It has the formula ZnO.
Contents
Properties
Physical
Zinc oxide is white, powdery substance. It is insoluble in water. It will decompose before melting when heated to 1975°C, or to 950°C with carbon.
Chemical
Zinc oxide is amphoteric. It reacts with acids to form salts of zinc, and with bases to form zincates. It is used industrially to make zinc sulfide through reaction with hydrogen sulfide.[1]
Crystalline zinc oxide is thermochromic, changing from white to yellow when heated and in air reverting to white on cooling. This color change is caused by a small loss of oxygen to the environment at high temperatures to form the non-stoichiometric Zn1+xO, where at 800 °C, x = 0.00007.
Availability
Like most chemicals, zinc oxide can be purchased from scientific suppliers like Elemental Scientific in pure form.[2] It can also be purchased from art and ceramic suppliers, since it is used as a pigment and in glazes. However, some ZnO pigments are calcinated, which makes them inert to most reagents.
Preparation
Zinc oxide can be made in the lab by heating zinc carbonate or zinc hydroxide at high temperatures.
A more clean method involves electrolyzing a solution of sodium bicarbonate with a zinc anode. Zinc hydroxide and hydrogen gas are produced. The zinc hydroxide is pyrolyzed to zinc oxide.
It is also a side product of zinc melting. If the floating slag becomes yellow at high temperatures, then it contains zinc oxide.
Projects
- Thermochromism demonstration
- Make zinc oxide eugenol
- Make zinc metal
- Grow large crystals via hydrothermal growth[3]
- Ceramic materials
Handling
Safety
Zinc oxide is non-toxic, but it's generally best to avoid breathing it in as it could potentially irritate the airways. Inhalation of hot zinc oxide when melting zinc may lead to metal fume fever. Always wear a protection mask when melting zinc metal.
Impure zinc often contains cadmium, which is extremely toxic to oneself and the environment.
Storage
Zinc oxide does not require special storage, though it should be kept away from any acidic vapors. Plastic bottles are good for storage.
Disposal
Zinc oxide poses little toxicity to the environment, and can be dumped in trash. Technical grade ZnO may contain traces of cadmium and lead oxides, and should be taken to hazardous waste disposal centers.
References
- ↑ http://en.wikipedia.org/wiki/Zinc_oxide
- ↑ http://www.elementalscientific.net/store/scripts/prodView.asp?idproduct=2857
- ↑ http://onlinelibrary.wiley.com/doi/10.1111/j.1151-2916.1964.tb14632.x/abstract
