*FWOOSH*
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Polyacrylate as alternative dessicant?
Just curious if anyone had ever tried this, as recycling polyacrylate balls sounds a lot less messy than MgSO4 and the price is just about as
negligible. Haven't seen anyone trying or asking about it when I looked around.
Not sure if I'd want to use it to dry a solution out, more like desiccant chamber usage, be pretty easy to see how saturated it was too, since the
most common types expand as they become saturated.
Any thoughts?
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Mailinmypocket
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I don't believe it would work very well, or quickly if it does work. The material absorbs water at an insane rate with ridiculous capacity but as far
as removing water vapor from the air it is hard to say. I could always put a small beaker of sodium polyacrylate crystals next to a beaker of water in
a desiccator overnight and see if there is a change in mass or something, if you like?
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*FWOOSH*
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That would be much appreciated 
I wasn't too sure how well it would work myself, but it doesn't seem like anyone's tried it yet.
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Mailinmypocket
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Well, there we go. 1.73g of sodium polyacrylate next to a small dish of water. Both were placed in a small vacuum food container and the air was
pumped out (these things work wonders as small desiccators with NaOH by the way)
Ill wait 24h and weigh to see if we have an increase. I really can't see much happening though, otherwise wouldn't packages of baby diapers and the
like eventually go bad from absorbing moisture from the air?
*edit* Actually since you mentioned using it in a drying chamber... A much more powerful and common desiccant for that application is NaOH. The cost
is much less than polyacrylate as well. We will see what happens for curiosity's sake, but in a drying chamber you are much better off with NaOH
 
[Edited on 16-9-2013 by Mailinmypocket]
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bfesser
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You're such a tease (rocks in frame).
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unionised
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I'm pretty sure this is the same polymer, and it dries out when exposed to air.
Not much of a desiccant.
http://www.sno-wonder.com/faq.asp
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Mailinmypocket
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You know- you are completely right! I forgot completely about how the gel reverts back to dry granules when left in the open, duh. Well that was a
waste of time for fart sakes!
Fwoosh, I think you have your answer 
Sorry bfesser, I didnt mean to tease with that rock(museum bought specimen a roommate left behind, it's amethyst in granite or something like it).
It's not all that nice really lol
Oh, and I went to check the polyacrylate in order to put it back into its jar. It is no longer free flowing and is clumpy, apparently it has a very
mild ability to absorb moisture from the air. Nothing like the usual desiccants though. Ill let it go and we what happens.
[Edited on 16-9-2013 by Mailinmypocket]
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*FWOOSH*
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@unionised
I guess I should have been a bit more specific  .
Polyacrylate has enormous water absorption capacity, but I'm aware that it dries out in air when saturated.
I was curious about its performance as the *dry* polymer, as dry as your other desiccants would normally be, and used in similar quantity.
That wouldn't require it to become anywhere close to fully saturated, wasn't looking to have it suck 200X its weight out of the atmosphere or anything
haha
@Mailinmypocket
Thanks for the tips! I just recently started putting my collection together so I don't have a whole lot of experience outside my lab classes.
Should be interesting to see what it looks like in the morning 
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Mailinmypocket
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Conclusion: it's a poor desiccant!
After 24 hours the weight of the material was 2.13g, meaning it absorbed 0.4g of water. The polyacrylate is no longer a free flowing powder but a
flimsy crumbly mass that can be picked up:
Having nothing left to do I tossed it into my glass of water and watched it gel up- very entertaining
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phlogiston
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Anecdotal evidence: the fact that baby diapers don't seem to bind significant amounts of moisture from the air even in the relatively wet climate I
live in supports that conclusion too.
-----
"If a rocket goes up, who cares where it comes down, that's not my concern said Wernher von Braun" - Tom Lehrer |
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*FWOOSH*
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Hooray Science!!!
Thanks Mailin, one less mystery in the universe
And still no practical lab use for sodium polyacrylate
[Edited on 18-9-2013 by *FWOOSH*]
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phlogiston
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clean up spills?
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"If a rocket goes up, who cares where it comes down, that's not my concern said Wernher von Braun" - Tom Lehrer |
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PHILOU Zrealone
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You all should have guessed from Raoult's laws (ebulioscopy) and from tonometry
laws ...
1°)The polyacrylate is a polymer and it displays a high molecular mass and thus its molality into a solvent like water should be very low... so
versus pure water the vapor tension will be a little more higher into the water gel (polyacrylate) than in pure water.
Although this might be dependant on the counter cation used on the carboxylic groups, their atomic weight and their dissociation level into water ...
H>Li>Na>K,...
2°)PA polymer may absorb some water from the air especially into a closed vessel with a beacker of water...but if you added some salt into the water
the molality of the water would be much higher and so the two beackers will compete for dehydration and the beacker holding the higher molality will
be more hygroscopic and dillute while the beacker with the lower molality will concentrate (loss of water).
At a certain point the vapour tensions of the two beackers will be equal and equilibrium is reached.
3°) If you put pure water into the closed vessel asside a gel (or a saturated salt solution); due to the non zero molality, the gel (or the salty
solution) will evaporate very much slower than the pure water beacker what will display full vapour tension; as a consequence after enough time the
water beacker will be dry and all the water evaporated by natural evaporation into the clossed vessel will be caught by the gel/salty solution.
4°) In an open container the level of humidity of the air is the competiting factor...sometimes it dehydrates the target sometimes it hydrates
it...If air is dry enough anything should be dehydratable at term because the system would be the universe and the target could never reach
equilibrium with its own vapour pressure.
PH Z (PHILOU Zrealone)
"Physic is all what never works; Chemistry is all what stinks and explodes!"-"Life that deadly disease, sexually transmitted."(W.Allen)
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Harristotle
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It is quite good for concentrating proteins with.
Fill a dialysis bag with your desired protein and then place on a bed of polyacrylate. Works wonders - I used to use it to concentrate ferritin.
If you want to go totally DIY, get a threaded 25mm pvc connector and some threaded pipe. Place a moistened cellophane sheet between the connector and
the pipe, and fill the lower part of the pipe with polyacrylate (or dry polyacrylamide, both will do). Cover the bottom of the pipe with a balloon (to
retain the polyacrylate, and allow expansion when it swells), then place your protein of interest in the top chamber.
Cellophane has pores of approximately 10 000 mw - so other polymers should also be concentratable like this (though precipitation and redissolution is
probably better for those as they don't have sensitive tertiary and quaternary structure that can be lost by rough treatment).
Cheers,
H.
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