Zinc hydroxide
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| Zinc hydroxide | |
|---|---|
| Image:Zinc hydroxide.jpg | |
| General | |
| Other names | |
| Molecular formula | Zn(OH)2 |
| Molar mass | 99.39 g/mol |
| Appearance | white powder |
| CAS number | [20427-58-1] |
| Properties | |
| Density and phase | 3.053 g/cm3, solid |
| Solubility in water | slightly soluble |
| Melting point | 125°C (decomposition) |
| Boiling point | ? |
| Hazards | |
| EU classification | not listed |
| NFPA 704 |    |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references |
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Zinc hydroxide (Zn(OH)2) is an inorganic chemical compound.
It is unusual in that, like zinc oxide, it is amphoteric. Thus it will dissolve readily in a dilute solution of a strong acid, such as HCl, and also in a solution of sodium hydroxide.
It can be prepared by adding sodium hydroxide solution, but not in excess, to a solution of any zinc salt. A white precipitate will be seen: Zn2+ + 2OH- → Zn(OH)2.
If excess sodium hydroxide is added, the precipitate of zinc hydroxide will dissolve, forming a colourless solution of sodium zincate: Zn(OH)2 + 2OH- → Zn(OH)42-. This property can be used as a test for zinc ions in solution, but it is not exclusive, since aluminium and lead compounds behave in a very similar manner.
One major use is as an absorbent in surgical dressings.
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