Most types of desiccation packages use silica gel, but are there any that use calcium oxide instead? Here's my reasoning:

  1. Calcium oxide absorbs water, forming calcium hydroxide.
  2. Adding a (used) package to water produces a slight amount of heat (I may be imagining this).
  3. The solution stays cloudy even after sitting for a while.
  4. The solution almost immediately turns clear upon addition of vinegar.

At this point, I'm pretty sure it is calcium oxide and hydroxide in this package, but I just wanted to make sure first. For point 2, I should note that it is very humid in the place that I live, so it would make sense that most of the calcium oxide is converted into calcium hydroxide, and therefore not much heat is produced.


1 Answer 1


Yes, calcium oxide can be used as an desiccant.

The following quote is an excerpt from this site:-

Calcium oxide is calcinated or recalcinated lime having a moisture adsorptive capacity of not less than 28.5% by weight. The distinguishing feature of calcium oxide is that it will adsorb a much greater amount of water vapor at a very low relative humidity than other materials. It is most effective where a low critical relative humidity is necessary, and were there is a high concentration of water vapor present.

Calcium oxide removes water from a package very slowly, often taking days to reach its maximum capacity. As calcium oxide adsorbs moisture, it swells. Proper desiccant packaging is required for effective use. For these reasons, its use has been limited to primarily the packaging of dehydrated foods.

This following is a table which compares the properties of various dessicants taken from this site:-

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And the following graph depicts the adsorption capacity of various dessicants:-

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For more information click on the following sites:-

  1. http://www.ohe-chem.co.jp/e_qa.html
  2. http://www.agmcontainer.com/support/selecting-desiccant
  3. https://www.usaemergencysupply.com/information-center/self-reliance/food-storage-frequently-asked-questions/types-of-desiccants

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