Lime, Calcium chloride, Table sugar.

Which one of these substances, when in the powdered form, makes the best dessicant?

According to wikipedia, sucrose has the highest solubility in water but i'm not sure as to how readily it absorbs air moisture. does anyone know about this?

Lime, Calcium chloride, Table sugar.

Which one of these substances, when in the powdered form, makes the best dessicant?

According to wikipedia, sucrose has the highest solubility in water but i'm not sure as to how readily it absorbs air moisture. does anyone know about this?

Absolutely. Calcium chloride is the most hygroscopic of the ones you've listed. Of all the ones readily available, calcium oxide is best but it's also caustic. For drying foods, common salt and sugar are about equal with a slight advantage to the salt (sodium chloride). For any other commercial purpose, silica gel is best.

Thanks. How did you know all this? And for silica gel, how does it compare to calcium oxide?

PS I think I was wrong about the table sugar having the most solubility, since I forgot to convert to molar.

And what's the deal with calcium sulfate? Does anyone know?

Thanks. How did you know all this? And for silica gel, how does it compare to calcium oxide?


You're welcome. :)

Well, I wish I could claim some 'special' knowledge here but i can't. ;)

Once, while doing some lab work, I thought I knew the answer from classes long ago and all it took to verify it was to look it up in an engineering handbook. This time around I just remembered doing that and the results.

Pound for pound, calcium oxide is better because it not only absorbs it physically but chemically as well. Remember a term called "water of hydration?" That's the key.

But on a real pound/pound basis there's something that beats both of them but is a little harder to find, that's all. It's the organic polymer that's used as the absorbent in diapers and women's sanitary napkins. We discussed it here in another thread quite a while back. It will absorb about 2,000 times it weight in water. (Takes up a lot of space, though.)