A desiccator or desiccant container is a chamber that removes water from chemicals or items. It is extremely easy to make a desiccator yourself using materials you probably have on hand.
Have you ever wondered why so many products come with little packets that say "Do Not Eat"? The packets contain silica gel beads, which absorb water vapor and keep the product dry. Including packets in packaging is an easy way of preventing mold and mildew from taking their toll. Other items would absorb water unevenly (e.g., parts of a wooden musical instrument), causing them to warp. You can use the silica packets or another desiccant to keep special items dry or to keep water from hydrating chemicals. All you need is a hygroscopic (water-absorbing) chemical and a way to seal your container.
Key Takeaways: How to Make a Desiccator
- A desiccator is a container used to maintain a low-humidity environment.
- Dessicators are simple to make. Basically, a dry desiccant chemical is sealed within a closed container. Objects stored within the container will not become damaged from moisture or humidity. To some extent, a desiccator can absorb water already stored within an object.
- Many desiccants are available, but they vary widely in terms of safety and cost. The safest chemicals to use include silica gel beads, calcium chloride, and activated charcoal.
- Desiccant chemicals can be recharged by heating in order to drive off the water.
Common Desiccant Chemicals
Silica gel is the most widely available desiccant, but other compounds work, too. These include:
- Silica gel (the beads in those little packets)
- Sodium hydroxide (sometimes sold as a solid drain cleaner)
- Calcium chloride (sold as a solid laundry bleach or a road salt)
- Activated charcoal
- Calcium sulfate (gypsum or plaster of Paris)
However, some of these chemicals are more effective and safer than others. Rice, for example, is extremely safe. It is often added to salt shakers as a desiccant to prevent water absorption, allowing the seasoning to flow through the shaker. Yet, rice has a limited ability to absorb water. Sodium hydroxide and calcium chloride are extremely effective, but sodium hydroxide is a caustic compound capable of producing chemical burns. Both sodium hydroxide and calcium chloride eventually dissolve in the water they absorb, potentially contaminating objects stored within a desiccator. Sodium hydroxide and calcium sulfate evolve considerable heat as they absorb water. If a lot of water is absorbed within a short amount of time, the temperature within the desiccator may spike dramatically.
In summary, for a basic home or lab desiccator, silica gel and activated charcoal may be the two best choices. Both are inexpensive and non-toxic and don't degrade upon use.
Make a Desiccator
This is extremely simple. Just place a small amount of one of the desiccant chemicals into a shallow dish. Enclose an open container of the item or chemical you wish to dehydrate with the container of desiccant. A large plastic bag works well for this purpose, but you could use a jar or any airtight container.
The desiccant will need to be replaced after it has absorbed all of the water that it can hold. Some chemicals will liquefy when this occurs so that you will know they need to be replaced (e.g., sodium hydroxide). Otherwise, you'll just need to switch out the desiccant when it starts to lose its effectiveness.
How to Recharge a Desiccator
Over time, desiccants become saturated with water from humid air and lose their effectiveness. They can be recharged by heating in a warm oven to drive off the water. The dry desiccant should be stored in a sealed container until use. It's best to expel all of the air out of the container, since it contains some water. Plastic bags are ideal containers because it's easy to squeeze out the excess air.
- Chai, Christina Li Lin; Armarego, W. L. F. (2003). Purification of Laboratory Chemicals. Oxford: Butterworth-Heinemann. ISBN 978-0-7506-7571-0.
- Flörke, Otto W., et al. (2008) "Silica" in Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a23_583.pub3
- Lavan, Z.; Monnier, Jean-Baptiste; Worek, W. M. (1982). "Second Law Analysis of Desiccant Cooling Systems". Journal of Solar Energy Engineering. 104 (3): 229-236. doi:10.1115/1.3266307
- Williams, D. B. G.; Lawton, M. (2010). "Drying of Organic Solvents: Quantitative Evaluation of the Efficiency of Several Desiccants." The Journal of Organic Chemistry 2010, vol. 75, 8351. doi: 10.1021/jo101589h