Mabus
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Desiccator question - height or surface?
Which have the best performance: A tall desiccator with a smaller surface or a wide-surface desiccator with short height?
By best performance I mean which will absorb water the fastest and if the position of the drying agent and the wet material inside the desiccator in
relation to the form of the desiccator influences the drying time (effect of vertical stacking vs horizontal stacking on drying time).
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LearnedAmateur
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All the dessicators I’ve seen are small form, like a crock pot kinda thing, and I’d say that leads to the fastest adsorption time. As with
anything to do with adsorbency, higher surface area is more effective. You’ll still want some depth to the desiccant though, as the moisture will
slowly move down towards the bottom until it equalises out. That’s all I really have to say on the matter though, never used a dessicator myself so
I’m just going off principle.
In chemistry, sometimes the solution is the problem.
It’s been a while, but I’m not dead! Updated 7/1/2020. Shout out to Aga, we got along well.
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Mabus
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I see. I have recently used a small wide cookie plastic box (900 ml) as a makeshift desiccator to dry 50 g of some pretty hygroscopic salt in 1.5
months using anh. CaCl2, without having to make the box air-tight. However, when I used a large (diameter equal to height) plastic bucket (10 l) to
dry 100 g of wet salt (double), I couldn't get any visible drying even after 3 months, even though I used 5 times more anhydrous CaCl2 than in the
small box. I've then moved the content to a smaller box (5 l), only this time the box is wide & short like the first one, and now after a couple
of weeks I'm finally getting some dry salt appearing on the surface. I'm positive the bucket isn't broken since I've tested for leaks and it sealed
properly as the CaCl2 was still dry after 3 months. Not sure why it failed to dry at least a bit in the large bucket.
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XeonTheMGPony
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Surface area, volume, temp gradients, vapor pressure all play a roll.
You want the smallest volume to keep the vapor close to the desiccant while providing a good temp gradient between the two with the largest surface
area possible.
IE: Round and flat like the vast majority of store bought desiccators/fruit dryers
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LearnedAmateur
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You could probably get away with using a bucket to dry if you periodically mix around your product to make sure the wet stuff comes to the top, if you
just leave it then it’ll hold onto the moisture more effectively. It’ll be something to play around with, but if it doesn’t work out then go for
the option(s) that do the job.
In chemistry, sometimes the solution is the problem.
It’s been a while, but I’m not dead! Updated 7/1/2020. Shout out to Aga, we got along well.
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KalleMP
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I wonder if fitting a fan blade from an old PC fan with a magnetic stirbar left at the bottom (elevate the desiccant a bit) might make for fast
drying.
I recently purchased a used lab type desiccator and have had some sodium acetate solution (about 10g in 100ml) with almost 200g of calcium chloride
desiccant. It has been about 2 weeks and the level of the solution has come down to about half but seems to have stopped dropping (maybe) so the
process is slow or I may have skimped on the CaCl.
The key is to have the air move past the product and the desiccant so that the vapour pressure of the water keeps attempting to equilibrate.
Another simple alternative would be a 40W light shining on one side (light and temperature sensitive products excluded) to get good convection flow.
I placed my desiccant in an opaque dish so am unable to see if it is already all deliquescent so next time I will dig out the large evaporating dish
to put in the bottom and think about fan or convection circulation.
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LearnedAmateur
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If you’re trying to dry sodium acetate then I’d recommend boiling the solution down until you get a wet solid - just make sure you keep it moving
whilst it precipitates out otherwise it will all come flying out once the solid mush gets too thick for the bubbles to escape easily. Obviously the
less water you start with in your product, the faster it will dry and you’ll need less dessicant overall.
In chemistry, sometimes the solution is the problem.
It’s been a while, but I’m not dead! Updated 7/1/2020. Shout out to Aga, we got along well.
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