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How to Specify a Desiccant

Desiccants are drying agents that come in either liquid or solid form. Solid desiccants are adsorbing compounds whereas liquids are absorbing compounds. Adsorption works by binding atoms from water molecules in the air to the surface of the desiccant solid. Absorbent desiccants undergo a physical or chemical change upon taking in water. Sodium metasilicate, calcium sulfate and calcium chloride are examples of absorbent compounds. A molecular sieve is a type of solid, adsorbent desiccant that can tolerate extreme temperatures before losing effect. Table salt is even considered to be a mild liquid desiccant that can be used for preserving food.

Instructions

- 1
  Assess the reactivity of your desiccant using literature on its chemical nature. Ideal desiccant compounds are inert, meaning they are stable and their reactivity is low. Solid desiccants, like aluminosilicate clay, will bind to water molecules, adsorb them and retain their structural properties. Liquid silica gel desiccants will undergo physical change, such as expanding, as a result of absorbing the water.
- 2
  Fill a small container with a few ounces of water then fill it entirely with the desiccant compound. Let the container sit for an hour or so. Desiccants have a high affinity for water molecules. They sustain dryness by effectively pulling moisture out of the air.
- 3
  Empty the container of all the compound onto a paper towel. Check the remaining water at the bottom of the container. If the water has been absorbed or adsorbed by your compound, then it is an effective desiccant.

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