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What Are Desiccants?

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  • Written By: Mary McMahon
  • Edited By: O. Wallace
  • Last Modified Date: 07 July 2014
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Desiccants are substances which draw in moisture from their surrounding environment. There are a number of uses for desiccants, ranging from preparing chemicals in a chemical plant to protecting moisture sensitive items during shipping. Some common desiccants include activated carbon, sodium perchlorate, calcium sulfate, and silica gel. Around the house, salt and rice are both desiccants, and have been used for their desiccating properties by many cultures historically. Salt, for instance, was a key component in mummification in Egypt, used to draw water out of bodies to slow or stop the rate of decay.

Dryness is often a desired property. Many objects are allowed to dry through evaporation, but water loss slows as the evaporation reduces the moisture content of the object to that of the surrounding environment. Once an object is as moist as the surrounding environment, it cannot lose any more water, and this is where desiccants can come in. Enclosing the object in a container with a desiccant will allow it to lose more water as the desiccant sucks fluid out.

One common use for desiccants is in shipping, where things may be damaged if they become moist. Desiccants are included in the packaging to draw out water, and can be discarded once the objects arrive at their destination. These products are also used in dehumidifiers, bringing down the moisture in the air by drawing in water. Desiccant cooling systems take advantage of this trait to lower the humidity to make warm temperatures feel less extreme.

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In addition to being drying, desiccants can also have other properties. Some are antifungal, antimicrobial, or antiviral, making them useful for a variety of applications. Many are not safe to eat, and are labeled accordingly so that people do not get confused. Some are treated with materials which will stain as the desiccants attract water, allowing people to see when the maximum amount of water has been absorbed.

In some cases, a desiccant bag or sachet can be refreshed by heating it to force it to release its water, allowing for reuse. Others are single use, and must be discarded once they have fulfilled their function. It is important to select a desiccant which is appropriate to the task, as people want to avoid corrosion, chemical reactions, and other problems which may occur if the wrong substance is used as a desiccant. Salt, for example, causes metal corrosion, which would make it unsuitable in settings where metal is present.

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Discuss this Article

anon326598
Post 4

Many people mistakenly believe silica to be poisonous. Silica actually is a mineral, silicon dioxide, and is a common component of many rocks and soils. It is one of the main components of sand. Silica itself is inert, but ingesting it can be dangerous because it can cause gastric distress and intestinal blockages.

The silica found in the packets of desiccators also might be coated with a potentially carcinogenic chemical called cobalt chloride that is used as a moisture indicator, and ingesting this would be ill-advised at best.

angelBraids
Post 3

Ugh, I once bought some food in a sachet, the type that have desiccant packs taped to the inside. I didn't realise and used scissors to cut across the top.

After I tipped the contents into the skillet I noticed the liquid was foaming and saw the little white pellets, which literally dissolved before my eyes.

Because I was starving I tried to just scoop that section out, but it was impossible to enjoy the rest as I convinced myself it tasted odd!

The next thing that worried me was whether I'd ingested any poison, which seemed unlikely considering it had been inside a food product. Guess I'm just a worry wart.

jennythelib
Post 2

@jholcomb - I'll assume you've tried the obvious things, like running your bathroom exhaust fan, if you have one, after showering, and putting rice in your salt shaker so your salt won't clump.

There are desiccant "dehumidifiers" that do not plug in. I haven't tried them myself, but some people swear by them. They are quite inexpensive; some hardware and general merchandise stores have them, or you can order them online.

Damp Rid is the brand I've heard of most. although I'm not sure if it actually qualifies as a desiccant. They have a bunch of different styles and sizes; there is some sort of chemical that you replace and it pulls water out of the air into a container. Good luck - excess humidity is so gross! Hope you find a way to get rid of some of it.

jholcomb
Post 1

I've seen those desiccant packs that come inside pairs of shoes. (You know, the ones that say "Silica Gel. Do Not Eat.")

I've been looking for a dehumidifier for my house, but they are surprisingly expensive. Are there non-electric options that can get some humidity out of the air without buying a pricy dehumidifier?

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