Calcium Chloride as Desiccant
George Kimeldorf
nutrients. My plan is to (1) put a small amount of calcium chloride
(CaCl2.2H20) in an "envelope" made from the filter paper used in coffee
makers, (2) put the envelope in an oven to drive out the moisture,
and (3) put the envelope in the jar with the capsules.
Will this work ok? If so, what temperature should the oven be and how
long should I "bake" the envelope? Is there any way to tell when the
desiccant has absorbed all the moisture it can absorb and hence needs
to be baked again? Or is this a half-baked idea?
Any other suggestions for a homemade desiccant?
Charlie Oakes
Kimeldorf) wrote:
CaCl2 is a good dessicant and is sold commercially for that purpose.
at 20-25 C the stable phase of hydrated CaCl2, in the presence of
aqueous soln, is the tetra-hydrate so just using CaCl2.2H2O out of
the can isnt as effective as dehydrating it further as you suggested.
to drive off 'all' of the H2O's you'll need to heat the salt to
greater than 250 C. it may take 24 hrs of heating. if you try to
crank the temp. to high at first you may find that the salt will
pop out of your vessel as it dehydrates. i wouldnt put the 'dry'
salt in a paper envelope if the container will be exposed to enough
moist air so that it rehydrates to the point of actually becoming
a saturated soln. i've left small beakers of 'dry' CaCl2 sitting
open in my lab and on rainy days a pool of soln would accumulate
in the beaker. if it was soggy for long enough all of the salt would
dissolve. so the short story is that it's a very good dessicant and
the way you can tell that it's finished absorbing is that it will
no longer be solid and as a consequence a paper container would be
a bad idea.
good luck, charlie oakes (oa...@lbl.gov)
John Vinson
when to stop: if it gets too much water it deliquesces into a
slimy solution, which would seep out of your filter paper. I
would suggest silica gel - it's cheap and readily avaliable,
insoluble, and renewable. I once bought a paint-bucket size can
of it, I think 10 lb., for drying flowers; and it's often found
in the dessicant packets in your kind of application.
Another good choice is flaked anyhdrous calcium sulfate (sold
commercially as Dri-Rite, among other brand names).
Avner Turniansky
>
> I need a desiccant for jars of capsules containing supplementary
> nutrients. My plan is to (1) put a small amount of calcium chloride
> (CaCl2.2H20)
I'd go for using plain old self-indicating Silica-Gel. Calcium Chloride
turns to wet junk after absorbing a lot of moisture, not something you'd
like in a nutrient-capsule's jar.
Charles Williams
pore size. The problem is that they have to be activated immediately
before use: I used to heat them to 220 deg C for 2 hours under high
vacuum (less than 1 mm Hg). However, they're easily
handled and are guaranteed not to go soggy.
-- Charles Williams