Difference between revisions of "Desiccant"
From Sciencemadness Wiki
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*Concentrated [[sulfuric acid]] | *Concentrated [[sulfuric acid]] | ||
*[[Copper(II) sulfate|Copper sulfate]] (anhydrous) | *[[Copper(II) sulfate|Copper sulfate]] (anhydrous) | ||
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*[[Magnesium sulfate]] | *[[Magnesium sulfate]] | ||
*[[Phosphorus pentoxide]] | *[[Phosphorus pentoxide]] | ||
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| Activated alumina | | Activated alumina | ||
− | | style="text-align: center;"| | + | | style="text-align: center;"| Basic or acidic |
| style="text-align: center;"| Medium | | style="text-align: center;"| Medium | ||
| style="text-align: center;"| High | | style="text-align: center;"| High | ||
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| [[Aluminium nitrate]] | | [[Aluminium nitrate]] | ||
− | | style="text-align: center;"| | + | | style="text-align: center;"| Slightly acidic |
− | | style="text-align: center;"|Medium | + | | style="text-align: center;"| Medium |
− | | style="text-align: center;"|Medium | + | | style="text-align: center;"| Medium |
− | | style="text-align: center;"|No | + | | style="text-align: center;"| No |
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| Bentonite clay | | Bentonite clay | ||
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| [[Calcium]] | | [[Calcium]] | ||
− | | style="text-align: center;"| | + | | style="text-align: center;"| Alkaline |
| style="text-align: center;"| High | | style="text-align: center;"| High | ||
| style="text-align: center;"| Very high | | style="text-align: center;"| Very high | ||
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| [[Calcium hydride]] | | [[Calcium hydride]] | ||
− | | style="text-align: center;"| | + | | style="text-align: center;"| Alkaline |
− | | style="text-align: center;"|High | + | | style="text-align: center;"| High |
− | | style="text-align: center;"|Very high | + | | style="text-align: center;"| Very high |
− | | style="text-align: center;"|No | + | | style="text-align: center;"| No |
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| [[Calcium nitrate]] | | [[Calcium nitrate]] | ||
− | | style="text-align: center;"|Neutral | + | | style="text-align: center;"| Neutral |
− | | style="text-align: center;"|Medium | + | | style="text-align: center;"| Medium |
− | | style="text-align: center;"|Medium | + | | style="text-align: center;"| Medium |
− | | style="text-align: center;"|Yes | + | | style="text-align: center;"| Yes |
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| [[Calcium oxide]] | | [[Calcium oxide]] | ||
− | | style="text-align: center;"| | + | | style="text-align: center;"| Alkaline |
− | | style="text-align: center;"|High | + | | style="text-align: center;"| High |
− | | style="text-align: center;"|High | + | | style="text-align: center;"| High |
− | | style="text-align: center;"|No | + | | style="text-align: center;"| No |
− | | | + | | style="text-align: center;"| Calcium oxide will only remove water from ethanol until 5000 ppm.<ref>Ford, S. G.; Marvel, C. S., Organic Syntheses; Wiley: New York, 1943; Collect. Vol. 11, p 373.</ref> |
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| [[Calcium sulfate]] | | [[Calcium sulfate]] | ||
− | | style="text-align: center;"|Neutral | + | | style="text-align: center;"| Neutral |
− | | style="text-align: center;"|Low | + | | style="text-align: center;"| Low |
− | | style="text-align: center;"|High | + | | style="text-align: center;"| High |
− | | style="text-align: center;"|Yes | + | | style="text-align: center;"| Yes |
| Very fast and efficient drying agent, but a lot of drying agent might be necessary | | Very fast and efficient drying agent, but a lot of drying agent might be necessary | ||
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− | | Cement (Portland) | + | | [[Portland cement|Cement (Portland)]] |
− | | style="text-align: center;"|Alkaline | + | | style="text-align: center;"| Alkaline |
− | | style="text-align: center;"|Medium | + | | style="text-align: center;"| Medium |
− | | style="text-align: center;"|Medium | + | | style="text-align: center;"| Medium |
− | | style="text-align: center;"|No | + | | style="text-align: center;"| No |
| Used in desiccators, cannot be used directly | | Used in desiccators, cannot be used directly | ||
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| [[Cobalt(II) chloride]] | | [[Cobalt(II) chloride]] | ||
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| style="text-align: center;"| | | style="text-align: center;"| | ||
| style="text-align: center;"| | | style="text-align: center;"| | ||
− | | style="text-align: center;"|Yes | + | | style="text-align: center;"| Yes |
| Mostly used as water indicator | | Mostly used as water indicator | ||
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| [[Copper(II) sulfate]] | | [[Copper(II) sulfate]] | ||
− | | style="text-align: center;"|Neutral | + | | style="text-align: center;"| Neutral |
− | | style="text-align: center;"|Low | + | | style="text-align: center;"| Low |
− | | style="text-align: center;"|Medium | + | | style="text-align: center;"| Medium |
− | | style="text-align: center;"|Yes | + | | style="text-align: center;"| Yes |
| Mostly used as water indicator | | Mostly used as water indicator | ||
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| [[Magnesium]] | | [[Magnesium]] | ||
| style="text-align: center;"| | | style="text-align: center;"| | ||
| style="text-align: center;"| | | style="text-align: center;"| | ||
− | | style="text-align: center;"| | + | | style="text-align: center;"| High |
− | | style="text-align: center;"|No | + | | style="text-align: center;"| No |
− | | Reaction is very slow, rarely used | + | | Reaction is very slow, rarely used; Mostly used for removing traces of water |
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| [[Magnesium sulfate]] | | [[Magnesium sulfate]] | ||
− | | style="text-align: center;"|Neutral | + | | style="text-align: center;"| Neutral |
− | | style="text-align: center;"|High | + | | style="text-align: center;"| High |
− | | style="text-align: center;"|Medium | + | | style="text-align: center;"| Medium |
− | | style="text-align: center;"|Yes | + | | style="text-align: center;"| Yes |
| Good multipurpose drying agent; exists in powder and granular form; has the ability to absorb a lot of water | | Good multipurpose drying agent; exists in powder and granular form; has the ability to absorb a lot of water | ||
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| [[Magnesium chloride]] | | [[Magnesium chloride]] | ||
− | | style="text-align: center;"|Neutral | + | | style="text-align: center;"| Neutral |
− | | style="text-align: center;"|High | + | | style="text-align: center;"| High |
− | | style="text-align: center;"|Medium | + | | style="text-align: center;"| Medium |
− | | style="text-align: center;"|Yes | + | | style="text-align: center;"| Yes |
| Deliquescent | | Deliquescent | ||
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| [[Molecular sieve|Molecular sieves]] | | [[Molecular sieve|Molecular sieves]] | ||
− | | style="text-align: center;"| | + | | style="text-align: center;"| Weakly basic |
− | | style="text-align: center;"|High | + | | style="text-align: center;"| High |
− | | style="text-align: center;"|High | + | | style="text-align: center;"| High |
− | | style="text-align: center;"|Yes | + | | style="text-align: center;"| Yes |
− | | | + | | Drying takes hours to days; Unsuitable for drying ketones |
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− | + | | [[Potassium carbonate]] | |
− | + | | style="text-align: center;"| Acidic | |
− | + | | style="text-align: center;"| Medium | |
− | + | | style="text-align: center;"| High | |
− | + | | style="text-align: center;"| No | |
− | + | | Good for thoroughly drying predried compounds | |
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− | | [[Potassium]] | + | |
− | | style="text-align: center;"| | + | |
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− | | style="text-align: center;"|No | + | |
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| [[Potassium carbonate]] | | [[Potassium carbonate]] | ||
− | | style="text-align: center;"|Alkaline | + | | style="text-align: center;"| Alkaline |
− | | style="text-align: center;"|Low | + | | style="text-align: center;"| Low |
− | | style="text-align: center;"|Medium | + | | style="text-align: center;"| Medium |
− | | style="text-align: center;"|Yes | + | | style="text-align: center;"| Yes |
| Only for alkaline compounds | | Only for alkaline compounds | ||
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| [[Potassium hydroxide]] | | [[Potassium hydroxide]] | ||
− | | style="text-align: center;"|Alkaline | + | | style="text-align: center;"| Alkaline |
− | | style="text-align: center;"|High | + | | style="text-align: center;"| High |
− | | style="text-align: center;"|High | + | | style="text-align: center;"| High |
− | | style="text-align: center;"|Yes | + | | style="text-align: center;"| Yes |
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| [[Silica gel]] | | [[Silica gel]] | ||
− | | style="text-align: center;"| | + | | style="text-align: center;"| Weakly acidic |
− | | style="text-align: center;"| | + | | style="text-align: center;"| High |
− | | style="text-align: center;"| | + | | style="text-align: center;"| Medium |
− | | style="text-align: center;"|Yes | + | | style="text-align: center;"| Yes |
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| [[Sodium]] | | [[Sodium]] | ||
− | | style="text-align: center;"| | + | | style="text-align: center;"| Alkaline |
− | | style="text-align: center;"| | + | | style="text-align: center;"| High |
− | | style="text-align: center;"| | + | | style="text-align: center;"| Very High |
− | | style="text-align: center;"|No | + | | style="text-align: center;"| No |
| More often used to remove traces of water from aprotic solvents | | More often used to remove traces of water from aprotic solvents | ||
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| [[Sodium hydroxide]] | | [[Sodium hydroxide]] | ||
− | | style="text-align: center;"|Alkaline | + | | style="text-align: center;"| Alkaline |
− | | style="text-align: center;"|High | + | | style="text-align: center;"| High |
− | | style="text-align: center;"|High | + | | style="text-align: center;"| High |
− | | style="text-align: center;"|Yes | + | | style="text-align: center;"| Yes |
| Very effective for basic compounds, such as amines; caustic | | Very effective for basic compounds, such as amines; caustic | ||
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| [[Sodium oxide]] | | [[Sodium oxide]] | ||
− | | style="text-align: center;"| | + | | style="text-align: center;"| Alkaline |
− | | style="text-align: center;"| | + | | style="text-align: center;"| High |
− | | style="text-align: center;"| | + | | style="text-align: center;"| Very High |
− | | style="text-align: center;"|No | + | | style="text-align: center;"| No |
− | | | + | | More effective when used to dry compounds predried with another desiccant |
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| [[Sodium sulfate]] | | [[Sodium sulfate]] | ||
− | | style="text-align: center;"|Neutral | + | | style="text-align: center;"| Neutral |
− | | style="text-align: center;"|High | + | | style="text-align: center;"| High |
− | | style="text-align: center;"|Low | + | | style="text-align: center;"| Low |
− | | style="text-align: center;"|Yes | + | | style="text-align: center;"| Yes |
| Used to dry solvents; Requires lots of it; only good for predrying; | | Used to dry solvents; Requires lots of it; only good for predrying; | ||
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| [[Sulfur trioxide]] | | [[Sulfur trioxide]] | ||
− | | style="text-align: center;"| | + | | style="text-align: center;"| Acidic |
− | | style="text-align: center;"|High | + | | style="text-align: center;"| High |
− | | style="text-align: center;"|Very high | + | | style="text-align: center;"| Very high |
− | | style="text-align: center;"|No | + | | style="text-align: center;"| No |
| Tends to form a mist of sulfuric acid in contact with moist air | | Tends to form a mist of sulfuric acid in contact with moist air | ||
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| [[Sulfuric acid]] (concentrated) | | [[Sulfuric acid]] (concentrated) | ||
− | | style="text-align: center;"|Acidic | + | | style="text-align: center;"| Acidic |
− | | style="text-align: center;"|High | + | | style="text-align: center;"| High |
− | | style="text-align: center;"|High | + | | style="text-align: center;"| High |
− | | style="text-align: center;"| | + | | style="text-align: center;"| Yes, difficult |
− | | Used in desiccators, cannot be used to dry solutions directly | + | | Used in desiccators, cannot be used to dry solutions directly |
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| [[Zinc chloride]] | | [[Zinc chloride]] | ||
− | | style="text-align: center;"| | + | | style="text-align: center;"| Acidic |
− | | style="text-align: center;"| | + | | style="text-align: center;"| Low |
− | | style="text-align: center;"| | + | | style="text-align: center;"| Low |
− | | style="text-align: center;"|Yes | + | | style="text-align: center;"| Yes |
− | | | + | | Regenerating must be done in a stream of hydrogen chloride |
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<sup>1</sup>All compounds are considered anhydrous. | <sup>1</sup>All compounds are considered anhydrous. | ||
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[[Category:Desiccants]] | [[Category:Desiccants]] | ||
[[Category:Data tables]] | [[Category:Data tables]] | ||
+ | [[Category:Irritants]] |
Latest revision as of 21:08, 3 July 2017
A desiccant is a chemical which is hygroscopic enough to absorb water from hydrated compounds in the same sealed environment.
Common desiccants
- Calcium
- Calcium chloride
- Calcium oxide
- Concentrated sulfuric acid
- Copper sulfate (anhydrous)
- Magnesium sulfate
- Phosphorus pentoxide
- Silica gel
- Sodium and other alkali metals
- Sodium hydroxide
- Sodium oxide
Comparison
Substance1 | pH | Water capacity | Effectiveness | Reversible | Notes |
---|---|---|---|---|---|
Acetonitrile | High | High | Yes | Rarely used | |
Activated alumina | Basic or acidic | Medium | High | Yes | Can also be used to adsorb fluorides |
Activated charcoal | Medium | Medium | Yes | Will also adsorb other gasses | |
Aerogel | High | High | Yes | Expensive | |
Aluminium nitrate | Slightly acidic | Medium | Medium | No | |
Bentonite clay | |||||
Calcium | Alkaline | High | Very high | No | Reaction with water releases large amounts of hydrogen |
Calcium chloride | Neutral | High | Medium | Yes | Deliquescent; often used in drying tubes |
Calcium hydride | Alkaline | High | Very high | No | |
Calcium nitrate | Neutral | Medium | Medium | Yes | |
Calcium oxide | Alkaline | High | High | No | Calcium oxide will only remove water from ethanol until 5000 ppm.[1] |
Calcium sulfate | Neutral | Low | High | Yes | Very fast and efficient drying agent, but a lot of drying agent might be necessary |
Cement (Portland) | Alkaline | Medium | Medium | No | Used in desiccators, cannot be used directly |
Cobalt(II) chloride | Yes | Mostly used as water indicator | |||
Copper(II) sulfate | Neutral | Low | Medium | Yes | Mostly used as water indicator |
Magnesium | High | No | Reaction is very slow, rarely used; Mostly used for removing traces of water | ||
Magnesium sulfate | Neutral | High | Medium | Yes | Good multipurpose drying agent; exists in powder and granular form; has the ability to absorb a lot of water |
Magnesium chloride | Neutral | High | Medium | Yes | Deliquescent |
Molecular sieves | Weakly basic | High | High | Yes | Drying takes hours to days; Unsuitable for drying ketones |
Potassium carbonate | Acidic | Medium | High | No | Good for thoroughly drying predried compounds |
Potassium carbonate | Alkaline | Low | Medium | Yes | Only for alkaline compounds |
Potassium hydroxide | Alkaline | High | High | Yes | |
Silica gel | Weakly acidic | High | Medium | Yes | |
Sodium | Alkaline | High | Very High | No | More often used to remove traces of water from aprotic solvents |
Sodium hydroxide | Alkaline | High | High | Yes | Very effective for basic compounds, such as amines; caustic |
Sodium oxide | Alkaline | High | Very High | No | More effective when used to dry compounds predried with another desiccant |
Sodium sulfate | Neutral | High | Low | Yes | Used to dry solvents; Requires lots of it; only good for predrying; |
Sulfur trioxide | Acidic | High | Very high | No | Tends to form a mist of sulfuric acid in contact with moist air |
Sulfuric acid (concentrated) | Acidic | High | High | Yes, difficult | Used in desiccators, cannot be used to dry solutions directly |
Zinc chloride | Acidic | Low | Low | Yes | Regenerating must be done in a stream of hydrogen chloride |
1All compounds are considered anhydrous.
Gallery
- ↑ Ford, S. G.; Marvel, C. S., Organic Syntheses; Wiley: New York, 1943; Collect. Vol. 11, p 373.