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thunderfvck
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MgSO4
H2SO4 + Mg(OH)2 ---> MgSO4 + 2H2O
Will this work?
I can obtain Mg(OH)2 as milk of magnesia. And H2SO4 is in my basement.
I need a drying salt.
And CaCl2 just did not work for me...
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darkflame89
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hmmm...is there a need to dry the solution of MgSO4? You can just have to crystallise out of the solution.
You can try CaO as drying agent, or maybe anhydrous CoCl2
Ignis ubique latet, naturam amplectitur omnem.
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JDP
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Epsom salts
MgSO4 can be found as Epsom salts in like 5 pound quantitys for dirt cheap, so I don't see the reson for wasting good H2SO4. Unless you just in
it for the chemistry of it, in that case, yes your method will work.
~JDP
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thunderfvck
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REALLY. Epsom salt, huh?
Care to elaborate a tad?
...And MgSO4 IS a drying salt...that's why I need it.
[Edited on 17-3-2004 by thunderfvck]
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Saerynide
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I dont think he wants Epsom salt.
Epsom salt is the heptahydrate. It doesn't dry stuff very well 
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Esplosivo
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Epsom salts being the heptahydrate can be heated in a stream of dry air, such as in an oven, to remove the water of crystallization. After a while the
crystals should turn into a whitish 'powder'. This is the anhydrous state.
Just a tip but if you are going to use MgSO4 in a dessicator I doubt it would work efficiently. CaCl2 would be the best choice, being highly
hygroscopic and very easy to produce. Na2SO4 is another choice for a drying agent, though CaCl2 remains the best in my opinion.
The MSDS for MgSO4.7H2O:
http://ptcl.chem.ox.ac.uk/MSDS/MA/magnesium_sulfate_heptahyd...
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thunderfvck
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So epsom salt IS MgSO4? That's good. Very good.
It's not for a dessicator. I wish I had one though!
I want it to purify some ethanol, I mean that's one of the more immediate thigns I'd do with it. However, I understand that drying salts are
good friends to have so I'd like to stock up. I recall reading that CaCl2 forms "alcohols of crystallization" or something of that
sort. And so purifying ethanol with CaCl2 would be hopeless.
HCl + CaCO3 --> CaCl2 + CO2 + H2O
This has got to be right.
I stole some chalk from school, reacted with HCl and got this disgusting precipitate. It was greenish and very gross. I did not want to collect and
store this chemical so I threw it away. Was this supposed to be CaCl2?
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Esplosivo
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If the chalk was coloured it would have influenced the resulting mixture. Actually the easiest way to make a somewhat pure CaCl2 is to mix
hydrochloric acid with an excess of marble chips. After the reaction is complete (ie when the effervescence stops) filter the mixture and evaporate
the water. Hydrated CaCl2 will result. Continue heating up the solid and anhydrous CaCl2 will form. CaCl2 is a white solid, which is highly
hygroscopic. I use it as a dessicant myself, and I can assure you it works well.
The equation you posted is correct.
CaCl2 is high soluble in water, and therefore when formed it will surely NOT precipitate. The greenish ppt was probably some colouring agent. To get
the CaCl2 out of you mixture, filter it and evaporate the water from the resulting solution.
Btw, drying of alcohols is usuaally carried out using anhydrous sodium sulphate. This can made by mixing sodium carbonate/hydrogen
carbonate/hydroxide with dilute sulphuric acid until neutralization occurs. Then evaporate the water. Na2SO4 crystals will form, which when heated
in an oven will form the unhydrous powder.
[Edited on 17-3-2004 by Esplosivo]
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Saerynide
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I wouldnt bother waste precious HCl to get CaCl2. You can get CaCl2 for dirt cheap (like a couple bucks for a small bucket) in dehumidifiers like
Damprid.
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Organikum
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Dehydrating of salts for drying purposes is favorably done in a microwave. Spread the salt on the glassplate and nuke it on half power.
For drying alcohols CuSO4 is often used, it has the advantage that you can see if its wet as it turns blue then, anhydrous it is white/greyish.
Dont expect salts working fast in drying, also with strong stirring it will take at least a day until the job is done and often it will be necessary
to replace the salt with freshly dried one at least once. Distilling the dried solvent is advised as the salts are ALMOST insoluble in alcohol but not
completely.
Drying EtOH is tedious, timeconsuming and a pest as a pest can be. I prefer IPA as I can buy this unhydrous and it is also easier to dry when
wettened. Just salt it out.
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Tacho
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I doubt you will dry ethanol above 95%using drying salts. Do a search. You will find that drying ethanol is a pain. I remember that industrialy its
done distilating it with benzene, benzene forms an azeotrope with water that is separated.CaO or magnesium followed by distillation also comes to my
mind. Anhydrous MgSO4 will not work
Vogel's book (dowload it from Polverone's page) explain how it can be done in the lab.
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Organikum
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You get EtOH to over 99% anhydrous with CuSO4 - time and changing the salt are necessary though. This 99%+ alcohol can be made completely anhydrous
with NaOH - also time, weeks are needed here but it works. Also diethylether can be dried with NaOH this way to an extent being more dry than with
sodium wire.
No joke.
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thunderfvck
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Why is it preferable to dry the salt in a microwave?
And is it possible to overheat the salt? Will it break down when overexposed to heat, or am I okay when I leave it in the microwave for 6 minutes...?
[Edited on 24-3-2004 by thunderfvck]
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Esplosivo
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Overheat the salt!?!?! Aren't we talking of an ionic salt with a high, actually very high melting point?! It will not decompose in a microwave if
that is what you mean.
Are you sure you can dehydrate the compound in a microwave. Why not use a normal oven or heating the compound in a can over a hot flame?!
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thunderfvck
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Oh yeah. It's working beautifully. BEAUTIFULLY.
I had two choices of epsom salt. The stuff I got, used for constipation, and there was the big bags, for baths and stuff I guess. Is there any
difference?
Mine came in a nice, professional looking chemical bottle. The other stuff was in a clumsy bag.
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Esplosivo
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I normally get the same stuff used for constipations from a pharmacy. It seems to be of quite a high grade stuff (probably GPR). Nice to know the
water of crystallization is removed in a microwave.
Did decrepitation occur?
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thunderfvck
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Not that I noticed. But I wasn't around while it was in the microwave. There was some violent jumping of the crystals though, which was pretty
neat. There wasn't any booming cracks or anything though.
The stuff also clumped together which you're probably familiar with in the oven...I guess. It was a PAIN in the ass seperating all of it, thank
GOD I have a mortar and pestle though (just came in yesterday). Now I have a fine white powder. My right arm feels pretty beef now as well, thirty
minutes of crumbling up that stuff...oh man...
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Esplosivo
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Good. Are you gonna use the unhydrous magnesium sulphate for drying alcohols now. I like the idea, seems pretty cheap and neat. The grinding lol, that
will count as a little exercise  Yeah the 'clumping' is common even
when it is heated in an oven.
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Polverone
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The microwave is nice because it dehydrates the salt much faster than other means. 2 hours in an oven or <10 minutes in a microwave, take your
pick.
Sodium acetate is almost the perfect example-compound for microwave drying. Take a bit of non-dry sodium acetate, add a little water, and toss it in
the microwave. The water boils off nicely until the whole mass suddenly goes anhydrous almost at once, leaving a light dry compound "fluffed
up" from the steam bubbles. It is now very easy to grind into a fine powder.
I did discover, though, that this doesn't work for NH4NO3: it melted and billowed white fumes after the water was gone.
Other salts, (MgSO4 for example) can also be less-well-behaved as they pop and spatter during drying. If you have a cheap microwave to dedicate to
chemicals, it is the best way to dry a number of salts.
PGP Key and corresponding e-mail address
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chemoleo
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Hmm, I always thought CaCl2 can NOT be made anhydrous by evaporating crystal water - I thought it decomposed similar to Aluminium chloride
hexahydrate, to CaO/OH and HCl?!?
But then, how is anhydrous CaCl2 made?? surely not by reacting the elements?
Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
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Esplosivo
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Calcium Chloride is a very common dessicant. It can be made as named previously. The calcium chloride solution is then made anhydrous by evaporating
off the water and then heating the remaining solid strongly (it usually melts if heated too strongly). It does not decompose during heating, and I can
confirm that from experience
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acx01b
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microwave is the best way to dry drying salts
microwave is the best way to dry drying salts
try with blue CuCl2: hard with heat to obtain completly white stuff, or you need to heat it for 5-10 min.
with microwave: 30sec
same with CaCl2: when you store it, after 1month it is really far to be dry... it is full of non-cristallized water!!
30sec microwave...
and you get it dried back.
work for 1gr-->10gr not more, or you need to dry it 5min under heat before if you dont want to destroy your microwave.
[Edited on 6-5-2004 by acx01b]
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thunderfvck
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I recently tried to dry my CaCl2 in the microwave and I broke the plate.
The stuff also jumped around wildly and made quite a mess.
Never again. CaCl2 is for the oven only.
I could probably use a better plate, but, nah. Being stubborn is fun.
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acx01b
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If when you heat it it jumps around, it will jump around too in your microwave
lol
thats what i learnt yeasterday trying to dry Na2So4....
but if there is no FREE h2o in your salt, it wont jump around.
microwave is the easiest way (20-30sec 800watt) to get dried MgSo4 from MgSo4.6H2O but if there is more than 6 mole of h2o for 1 mole of mgso4, it
will jump around in your microwave and you'll get quite a mess....
to prevent it, you can always cover it with a glass..
I DIDNT GET ANY BROKEN PLATE!!! but i didnt let it more than 5sec when it started to jump around
sorry anyway...... if you broken your plate
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praseodym
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Which will be the best drying agent in a desiccator, MgSO4, Mg(ClO4)2, CaH2 or LiAlH4?
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