Lion850
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Best drying agent to use in a desiccator?
I am using sodium hydroxide flakes as the drying agent in my desiccator, because it is readily available in 5kg quantities at reasonable cost. However
I get the impression that once the still solid NaOH is covered by water (which it 'sucked' out of the compound being dried) it becomes a lot less
effective. With the result that I have to open the desiccator and replace the wet, water covered NaOH with fresh flakes after some 12 hours if I am
drying something with a lot of water.
What can I use that will be more effective? I have 97% sulphuric acid (which in my opinion will increase the handling risk), phosphor pentoxide (which
I don't really want to use as it is not so easily obtained) and then calcium chloride, which is easy to get in bulk.
Has anyone experience with using calcium chloride as drying agent, how does it compare to sodium hydroxide?
Also to mention, for sake of completeness, that a vacuum is always maintained during the drying.
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B(a)P
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I have often used calcium chloride, it is cheap and readily available. I have also had good results from anhydrous magnesium sulfate, which I prepare
by drying the hydrate, which is also cheap and readily available. I have not tried sodium hydroxide so I can't give you a comparison.
This is worth a look https://lib.dr.iastate.edu/cgi/viewcontent.cgi?referer=https...
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Lion850
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Very interesting article, thank you. I will try calcium chloride some time.
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rockyit98
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MgSO4 is good. i make Anhydrous Magnesium sulfate is made from heating Kieserite slow up to 200C Kieserite a monohydrate of the salt.you can use
Epsomite aka Epsom salt , formula MgSO4ยท7H2O but they tend to liquefy before drying due to high number of water in the crystal lattice.
a pain in the butt s don't let them hydrate all the way use known amount mass of Anhydrous Magnesium sulfate and check to see how along they are.
CaSO4 is also good ,heat P.O.P up to it 250C and reuse aging and aging.
if you need powerful one use CaO. which can be regenerated heating up to 600C. and i'm not kidding it will suck all the water.
[Edited on 11-3-2020 by rockyit98]
"A mind is a terrible thing to lose"-Meisner
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Tsjerk
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You can dry magnesium sulfate heptahydrate in a microwave in minutes. Just blast the shit out of it until it stops fuming steam. Use a cover against
splashing. Sodium sulfate also works but splashes a lot worse compared to magnesium sulfate.
Calcium chloride is sold anhydrous, I wouldn't botter to dry it, it is cheap.
Calcium chloride is nice as it actually dissolves in its own water. As soon as the powder is covered by the water you have to change it. The Na and Mg
sulfates don't dissolve, but the are nice because the don't absorb ethanol... If that is important.
I would only use NaOH or sulfuric acid when I would have some gaseous acid or base I wanted to get rid of.
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