haydz - 3-5-2005 at 14:59
Hey guys,
I'm going to try and find a cheaper alternative (that works just as well or better) to "damp rid" they are the things you put in
closets, kitchens etc anywhere that you dont want moisture. Can you guys recommend some hygroscopic materials to do my experiment? Im thinking
ammonium nitrate, although the stuff I have is probably coated with some wax to prevent it. I presume you can just dissolve it in water and boil it
off? Potassium Hydroxide is another one I might try, but theres the problem of it heating up when exposed to water...
Any ideas?
chemoleo - 3-5-2005 at 15:41
Calcium oxide? Cheap, hygroscopic and nontoxic.
neutrino - 3-5-2005 at 16:57
I wouldn't recommend potassium hydroxide, as this is a very strong base and would be dangerous to handle, especially in the form of a
concentrated solution. Try calcium chloride (CaCl<sub>2</sub>
. It is a
cheap, strong desiccant that forms a convenient liquid on absorbing water.
runlabrun - 3-5-2005 at 17:13
The question was for an alternative to damp rid which is CaCl2 so suggesting CaCl2 as an alternative for damp rid is a bit silly now isnt it?
I would think Calcium oxide is a great alternative, chemoleo covered the important features, nontoxic... excellent!
-AC
Twospoons - 3-5-2005 at 17:38
No, the question was for a cheaper alternative! Bulk CaCl2 is cheaper than the nicely packaged stuff with the fancy printing and trademarked
name.
[Edited on 4-5-2005 by Twospoons]
12AX7 - 3-5-2005 at 18:49
Plaster of Paris may do it (or dehydrate it even further if you feel like firing a few pounds to 1200°F). Tends to cake up.. Other sulfates,
uh Epsom salts IIRC are hygroscopic and can be dehydrated on the stove.
Lime would certainly work, and keep down acid gasses too! 
Easy to manufacture
if you have a furnace: chuck some limestone in, blast to yellow heat for a few hours, crush and use.
Tim
S.C. Wack - 3-5-2005 at 19:06
If these figures are correct, you will have a hard time finding anything that works just as well or better for less than the cost of CaCl2.
http://chemdat.merck.de/mda/uk/labtool/table_dragent.html
neutrino - 4-5-2005 at 02:17
Plaster wouldn't work well, it only forms the hemihydrate (CaSO<sub>4</sub>.1/2H<sub>2</sub>O) under normal conditions.
It is a very strong desiccant, but doesn't absorb much.
S.C.: That’s an interesting chart, but remember that we only want to lower the humidity to a manageable level; we don’t need
P<sub>2</sub>O<sub>5</sub> here.
hodges - 5-5-2005 at 14:07
Some places sell calcium chloride for use in melting ice and it is a lot cheaper than DampRid this way. Check the labels, if you live in a place that
has snow (might have to wait quite a while in the northern hemisphere since its late spring).
sparkgap - 5-5-2005 at 17:08
He lives in New Zealand (see his profile), so I doubt people would be selling de-icing salt there.
sparky (~_~)
cyclonite4 - 5-5-2005 at 17:17
I'm in Australia. We're less likely to need CaCl2 here! I've found it sold as 'Dampsorb', although it was expensive (IMO,
$6/kg).
Picture
JohnWW - 5-5-2005 at 19:37
Actually, many parts of New Zealand, especially the west coast and mountains, have high rainfalls and humidity. And de-icing is needed in most inland
South Island areas and some central North Island areas in winter.