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sparkgap
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I have yet to hear of chlorates being used to dry things, but I can assure you that it is a waste of good hydrides to use them for drying stuff. The
hydrides have much more utility than that!!!!
sparky (~_~)
"What's UTFSE? I keep hearing about it, but I can't be arsed to search for the answer..."
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neutrino
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Actually, Mg(ClO<sub>4</sub> <sub>2</sub> is very
hydroscopic. IIRC, it is/was used industrially to dehydrate nitric acid.
We need a little background here: what is your budget, how much drying do you have to do, etc.
edit: Oops, the nitrate is used for nitric acid. The perchlorate is still very hydroscopic.
[Edited on 26-7-2005 by neutrino]
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Quibbler
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If you mix blue copper sulphate with dry alcohol you will find that the reaction goes the ther way - the alcohol acts as a drying agent and white
anhydrous CuSO4 comes out as a ppt. Oh and in a desicator you can't beat phosphous pentoxide.
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bio2
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.........Which will be the best drying agent in a desiccator, MgSO4, Mg(ClO4)2, CaH2 or LiAlH4?..................
Depends on how dry you need it and how often you do it.
For general use most commonly used is sulfuric acid or calcium sulfate (dryrite indicating). Dryrites capacity is low but dries more completely than
most other powders for general use such as sodium sulfate, MgSO4 etc.
You need to look at the residual moisture and capacity spec to determine what suits the purpose.
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praseodym
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I also believe it should be MgSO4 because the other 3 are simply more dangerous than MgSO4. The 2 hydrides produce hydrogen gas when being used as a
drying agent and H2 is flammable. perchlorates, on the other hand, is a strong oxidiser, hence, could be explosive. Am i right?
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neutrino
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| Quote: | Originally posted by praseodym
perchlorates, on the other hand, is a strong oxidiser, hence, could be explosive. Am i right? |
Yes, if they are mixed with combustibles.
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MadHatter
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Rock salt
I find that plain old rock salt is more than adequate for drying out ethanol. Besides, drying
the NaCl out in an oven is very fast at 300 F. This is a popular method for those making
their own gasohol.
From opening of NCIS New Orleans - It goes a BOOM ! BOOM ! BOOM ! MUHAHAHAHAHAHAHA !
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12AX7
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Howso? NaCl can only adsorb and occlude moisture (or ethanol for that matter), it doesn't hydrate except under pressure.
Tim
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neutrino
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It sounds like salting out to me. Add salt to an alcohol/water mixture and you get one layer of alcohol and one of salt water.
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Rosco Bodine
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Immerse some chunks of scrap aluminum in a moderately strong solution of
NaOH or spray with oven cleaner and then rinse , and immerse in dilute HCl .
Then amalgamate the aluminum fairly heavily by adding some mercuric chloride to the dilute HCl . When the surfaces are
very well plated with a mirror of liquid mercury , and evolving hydrogen freely ,
the chunks of amalgamated aluminum are removed and shaken free of excess liquid . The amalgamated Al chunks will
make a very active dessicant and deoxygenation reagent . The amalgam
should pull a partial vacuum within a closed dessicator as the Al binds with any moisture and oxygen in the confined space , therefore some sort of
valve for
a vacuum release will facilitate opening the dessicator later . The Al will be consumed and converted to a powder emerging from the film of mercury
as the
reaction proceeds .
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garage chemist
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That would be very useful indeed, were it not for the nastiness of mercury.
There once was a concept for a hydrogen generator for a fuel cell car which relied on the reaction of amalgamated aluminium with water.
The idea had to be abandoned because the exhaust gasses from the fuel cell drastically exceeded every safe level for mercury vapors! 
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Rosco Bodine
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You can recover most of the mercury by simply dissolving the residue in HCl , leaving a small globule of mercury at the
bottom of the AlCl3 solution . The AlCl3 solution can be kept for other uses , such as being the precursor for Aluminum Chlorophosphate refractory
binder , after treatment with phosphoric acid .
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praseodym
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If it is for drying the atmosphere, would magnesium sulphate or magnesium perchlorate be a better drying agent?? Is magnesium sulphate only used to
dry organic substances??
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UnintentionalChaos
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Holy crap. I wish somebody would have warned me about MgSO4 fusing together like that. I dried about 500g of it in the oven in a small casserole dish
and it took several minutes of chiseling to get underneath an edge and pry the block up. I wish I could get anhydrous isopropanol here but it only comes with 30% water. Still, it is much easier to get than ethanol (underage
still, or id go buy vodka). So that leads me to drying out isopropyl with MgSO4. The epsom salts are dirt cheap from the pharmacy so I like the idea
of using it as a dehydrating agent.
Also, Saerynide mentioned before about how you can get CaCl2 from room dehumidifiers. If you look around in hardware stores or even supermarkets, you
may be able to find pure CaCl2 for use as road de-icer. It looks exactly like the stuff in the room dehumidifiers (the way its pelletized) so I assume
they may have bought it from exactly the same chemical company, but I can get 4 1/2 kg of it for $8 (US) instead of maybe 300g maximum from a
dehumidifier for $2.80.
Another idea for cheap solvents is n-heptane. I don't know if its properties differ drastically from benzene, but it makes a nifty nonpolar solvent.
Look in art supply stores. It is used as rubber cement thinner. Not terribly easy to find because many other products are marketed that contain some
n-heptane or petroleum distillates that do the same thing. The art supply store near my college campus carries it at a liter for $6 (US). They also
have turpentine, but I'm not particularly sure how useful that might be.
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cnidocyte
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Can you dry polar solvents with MgSO4 and other common drying agents? I was under the impression that drying agents absorb all polar liquids making
them suitable only for drying non polar liquids. Is this how it is or do these drying agents selectively absorb water?
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Rogeryermaw
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how well would MgSO4 work in a tube for drying gasses such as NH3 and Cl2? i was looking to generate chlorine from TCCA + HCl and NH3 from NH4NO3 +
NaOh. if not, what would be ideal for this purpose?
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Arthur Dent
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I've tried the "gradual heating" method with sodium bi to turn it into carbonate and it worked. Starting with a 500g pack of Cow Brand in a pyrex
plate, I started with the plate in the regular oven for one hour at 150F, then stirred its content, then 1h at 200F, and again 1h at 250F and so on,
and 7 hours later, I had substancially less material but it did not congeal into one solid mass, it remained fluffy powdery (probably because of the
constant stiirring).
So I was wondering if that smooth, gradual heating method with constant stirring would work with plain old epsom salt to make it somehow anhydrous
without turning it into a solid rock? For now, my official "dessicator" apparatus is a large ziploc bag with a dollar store CaCl2 damp trap, but I do
intend to upgrade to a real vacuum dessication apparatus soon (maybe tomorrow)... so I'll need a selection of efficient drying agents.
Robert
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ScienceSquirrel
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Sodium bicarbonate loses water and carbon dioxide and the carbon dioxide keeps it fluffy, the soda ash formed is very fine indeed.
Epsom salts is a hydrate and tends to melt in its own water of crystallisation.
I think if you warmed it slowly it would start to effloresce to form the monohydrate which would then form a fluffy powder.
Here are the melting points;
http://en.wikipedia.org/wiki/Epsom_salt
I would try 120 to 130 until I was sure that quite a lot of water had been lost and then 175 - 190 and then heat it up to 250 -300 C to finish the
job.
You can use a set of lab scales to follow the dehydration, I have checked on the complete decomposition of sodium bicarbonate using scales. Do not
forget to let the sample cool before weighing.
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mr.crow
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Quote: Originally posted by Arthur Dent  |
So I was wondering if that smooth, gradual heating method with constant stirring would work with plain old epsom salt to make it somehow anhydrous
without turning it into a solid rock? For now, my official "dessicator" apparatus is a large ziploc bag with a dollar store CaCl2 damp trap, but I do
intend to upgrade to a real vacuum dessication apparatus soon (maybe tomorrow)... so I'll need a selection of efficient drying agents.
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CaCl2 and NaOH are great for desiccators, very hygroscopic. NaOH also absorbs acid fumes. I'm not sure how well MgSO4 works in this application so I
don't think its necessary. Just for drying organic solvents.
Don't worry about turning into a solid rock, its breaks apart easily. Put it in a ziplock bag and use a hammer or blocks of wood.
Double, double toil and trouble; Fire burn, and caldron bubble
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