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 cupboard which is damper than it ought to be.
What I'm left with after some time is a liquid and a solid mass.
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?
Are there like to be any nasty substances released into the air as it dries?
Why am I left with a solid and a liquid, not just some dissolved calcium chloride?
So, the crystals started absorbing moisuture, to the point of being dissolved in the moisture they were absorbing.
As this happens, the stuff heats up (apparently this reaction produces a lot of heat) and the water becomes super-saturated, and continues to dissolve more of the crystals.
Then it starts cooling down, and as it cools down some of the calcium chloride precipitates out of the water.
Anyway. Mere radiator won't cut it. Take it all out, and place in a flat baking tray or something, and place covered in an oven at 150C till dry. Then break up and put the
These things are truly crap. If you redry them in the house all the water vapour absorbed is dumped back into the air again.
If you keep using it, buying bagged lime from B&Q may prove cheaper. But just as poor a performer. Fwiw quicklime would be more effective, though less safe.
Not really - far too complicated! The crystals absorb moisture until they start to dissolve, the liquid thus produced is also hydroscopic and continues to absorb water until the crystals have all dissolved. After that the liquid still absorbs further moisture, but with reducing affectivity as the concentration of calcium chloride reduces.
I was once given one of those 'throwaway' dehumidifier containers once. It had a mark on the side about 1/2 way up, when the level reached the mark it was time for a new one.
No, the solid mass is a mixture of calcium sulphate and calcium carbonate -- basically trash impurities, because the "calcium chloride" sold for these things is far from pure.
If you were to heat the calcium chloride solution and evaporate it, you could recover the calcium chloride and re-use that. OTOH you'd probably have to pay the energy costs of doing so. If you had a big damp problem and a source of waste heat, then it _might_ start to make sense.
Leave it. What may make more difference is to take some packing tape, and go over the door edge insides, so that you have half on the door, half off the door. Then fold over the exposed edge of tape, so you have a draughtproofing seal. This may give some hope of the dehumidifier thing working, though it'd really need a vapour barrier to do any good at all.
from what I've seen of thesse things, they do absorb water vapour, but the amount of absorption is only a small proportion of the damp present, so they have approximately no effect on the situation. Theyre basically junk products.
I bought an electric dehumidifier from ALDI a month or so ago for under =A320. It collects about 150ml of water from our front room in a 7 hour period (over night). It seems to have no effect on condensation levels on our single glazed bay window, which was the purpose of the purchase.
I have several dishes of calcium choride under the floor in my narrowboat. it does keep it dry down there. But that it an environment where new water vapour enters only slowly so only a small amount of dehydration is needed.
As others have pointed out, calcium chloride is deliquessant, not merely hygroscopic; it absorbs so much water that it completely dissolves in it.
I use it (in tubs) in the boiler of my steam roller. (over winter) It keeps the RH close to zero and effectively stops the steel boiler rusting internally. The crystals last almost 6 months because the boiler is just about air tight, give or take some small leakage from gland packings etc.
Peltier? The heat from the hot side conducts back across when the power cycles off and de-frosts it. Woefully inefficient on power, but a neat little minimal design.
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?
See later for the likely chemistry.
Two tenths of bugger all.
No.
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.
If this was true, the calcium has to go out of solution too, as half of the CaCO2. For each molecule of CaCO2 that's produced, you've got to have an atom of Chlorine that's released into the air (after the solution is saturated by chlorine)
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