Difference between revisions of "Desiccant"
(reactivating) |
(→DIY Desiccants: a bit) |
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** Old silica gel uses pink/blue indicator colours | ** Old silica gel uses pink/blue indicator colours | ||
** New silica gel uses brown/yellow-brown indicator colours | ** New silica gel uses brown/yellow-brown indicator colours | ||
| + | * Non-indicator silica gel is occasionally seen. | ||
| + | * Easy to dry for re-use | ||
| Line 18: | Line 20: | ||
'''Hydrated lime''' | '''Hydrated lime''' | ||
* aka bagged lime | * aka bagged lime | ||
| + | * Quicklime can absorb more water, but is much more reactive, and can be a fire risk if it gets wet. | ||
| + | * Reactivation not an option. | ||
| Line 24: | Line 28: | ||
'''Magnesium sulphate''' | '''Magnesium sulphate''' | ||
| + | * Epsom salts | ||
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'''Caustic soda''' | '''Caustic soda''' | ||
| − | |||
==Reactivating== | ==Reactivating== | ||
Revision as of 01:05, 16 March 2008
Desiccants are useful for keeping small closed spaces dry, such as tool storage containers. Desiccants absorb water vapour, and then need drying out to work again, usually with heat. Some desiccants change colour when saturated.
DIY Desiccants
Silica Gel
- Normally contains a wet/dry indicator
- Old silica gel uses pink/blue indicator colours
- New silica gel uses brown/yellow-brown indicator colours
- Non-indicator silica gel is occasionally seen.
- Easy to dry for re-use
Anhydrous Calcium Sulphate
- Also known as Plaster of Paris, Gypsum & 'Drierite'
Magnesium Perchlorate
Hydrated lime
- aka bagged lime
- Quicklime can absorb more water, but is much more reactive, and can be a fire risk if it gets wet.
- Reactivation not an option.
Calcium chloride
Magnesium sulphate
- Epsom salts
Bentonite
- aka Montmorillonite clay
Molecular sieves
Caustic soda
Reactivating
Desiccants must be dried when saturated so they can absorb water again. There is considerable variation in what this entails.
Sillica Gel
Silica gel is dried in an oven at 120-150C. Non-indicating silica may be dried at higher temps, though there seems little reason to do so.
Sticking to 120C is wisest to minimise risk of package damage.
Lime
Lime requires over 1000C to dry it, so reactivation is not a realistic proposal.
More Desiccants
- Sulphuric Acid
- Activated alumina
- Benzophenone
- Calcium hydride
- Copper(II) sulfate
- Lithium hydride
- Magnesium
- NaK, a sodium-potassium alloy
- Phosphorus pentoxide
- Potassium
- Potassium carbonate
- Sodium
- Sodium chlorate
- Sodium hydroxide
- Sodium sulfate
- sodium-benzophenone