In article
, D.M.
Procida wrote:
I have a little plastic thing from Woolworths into which I pour calcium
chloride crystals, to act as a moisture absorber in an under-stairs
Calcium chloride is a pretty dodgy chemical to have around the
house. I'd expect it to find buckets of it in my father's house
(ex-industrial chemist, with a wife who's learned over 50 years to put
containers of chemicals back in the cupboard without opening them.
Are you really really certain that this device recommends use of
granular calcium chloride?

cupboard which is damper than it ought to be.

What I'm left with after some time is a liquid and a solid mass.

See later for the likely chemistry.

If I pour off the liquid, and leave the solid mass in a warm dry place,
say on top of a radiator, will it be any good at absorbing moisture from
the air once again?

Two tenths of bugger all.

Are there like to be any nasty substances released into the air as it
dries?

No.

Why am I left with a solid and a liquid, not just some dissolved calcium
chloride?

Calcium chloride will absorb copious water from the atmosphere. The
resulting nearly neutral solution of CaCl2 will pick up small amounts of
CO2 from the atmosphere, which will produce a precipitate of calcium
carbonate. That'll be your solid residue.
Calcium carbonate itself is not harmful, but with the chloride
you'll have a mix that'll dehydrate your skin pretty damned quick. And if
you get it into a cut, you'll really know about it. Get it in your eye (or
the inquisitive brat's eye) and you'll have fun trying to get your eye
under the shower while screaming in pain. It'd not be easy to blind
yourself, but by no means impossible.
Refer to previous description of the ex-industrial chemist : Dad
and I wouldn't be bothered about such stuff round the house, but we'd keep
it under lock and key.

Your mileage may vary, but I wouldn't use CaCl2 as a domestic
dehydrating material. I doubt Dad would either.

--
Aidan
Aberdeen, Scotland
Written at Fri, 08 Dec 2006 00:22 GMT, but posted later.