cokezero
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Purifying CaCl2
I have recently bought a mixture of CaCl2 and NaCl, in the hope I can selectively obtain just CaCl2.
I have thought up a plan to do this and I would like your opinions.
Both CaCl2 and NaCl are souble in water. I was think that I could preform the reaction below, as this would leave a precipitate of Ca(OH)2 as it is
rather insouble.
CaCl2 (aq) + 2NaOH (aq) -----> Ca(OH)2 (s) + 2 NaCl (aq)
First question I have is this reaction going to occur spontaneously, without heating etc. ?
As the Ca(OH)2 is insouble I would be able to collect this leaving behind the NaCl. To get the Ca(OH)2 back to CaCl2 I was thinking I could react it
with HCl.
Ca(OH)2 (s) + 2HCl (aq) -----> CaCl2 (aq) + 2H2O (l)
And then boil off all the water, leaving CaCl2.
What do you think?
Thanks in advance
[Edited on 23-12-2010 by cokezero]
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Magpie
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I think your scheme would work. CaCl2 forms a hydrate with water so you would then have to heat it in an oven hot enough to drive off the water.
Unless you just want to do this for fun it seems like a laborious way to get anhydrous CaCl2. I bought about 10lbs dirt cheap as a hardness increaser
for swimming pools.
The single most important condition for a successful synthesis is good mixing - Nicodem
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cokezero
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Ok thanks for the heads up about the water.
The main reason I am doing it this way is I am having trouble finding "pure" substances here in Australia. =/
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User
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I can hardly imagine that it is so hard to get..
This substance is so widely used.
Your method seems rather expensive.
Have you ever looked for moisture absorber ?
In a lot of countries this is near pure CaCl2.
The food industry also uses this this substance.
I guess you haven't looked thoughroughly enough.
If you plan to use HCl , why not react CaCO3 with it.
CaCO3 + 2 HCl --> CaCl2 + CO2 + H2O
This would be cheaper, easier and quicker.
You will be left with only water and the substance you are after.
What a fine day for chemistry this is.
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Bismuth
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It's readily available in its pure form from pool stores here in Victoria. It is sold in quite large quantities to increase the hardness in swimming
pools. You may also find it at a homebrew store, along with many other useful reagents that you could use.
I can assure you, with a bit of research and initiative you can acquire almost every chemical in Australia that other fellow chemists possess in other
countries. Check your U2U.
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cokezero
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I bought mositure absorber but it was only 60% CaCl2 the other 40% was NaCl.
Thanks for the other reaction User.
Thanks for the email Bismuth.
I have been interested in setting up my own home lab for a while and have just started this week =D So I am pretty new to finding all these chemicals
I so desire.
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User
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Welcome to the world of home chemistry 
Obtaining chemicals can be a study of its own.
Honesty or having a good story gets you a long way.
I have this little hobby shop nearby that can supply me with lots of reagents.
First time I walked in I somehow ended up with coffee and a nice conversation with the owner.
I told him about my hobby, study etc. he was enthusiastic about the things I told him.
Ever since he supplies me with a lot of reagents.
I give him a list with the stuff i need, and he even calls me to tell wether or not he can deliver it 
Knowing the application of chemicals can build a decent story for obtaining them without too much suspicion.
Still this is something i personally always watch out for, for example when buying fertilisers.
I always pay cash and try to look casual, maybe I am just paranoia sometimes.
My advice would be to stay of the record as much a possible.
Be selective when it comes to suppliers.
[Edited on 23-12-2010 by User]
What a fine day for chemistry this is.
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cokezero
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| Quote: | | Obtaining chemicals can be a study of its own. |
Yes, I am starting to realise this.
Thanks for the advice.
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dann2
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Ca Chloride also available from ceramics material suppliers
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bbartlog
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You would end up using up a bunch of HCl and NaOH, which seems wasteful.
If you really just have NaCl + CaCl2 and not a bunch of unknown impurities, I would suggest leaching out the CaCl2 with 95% ethanol. CaCl2 is soluble
in alcohol, NaCl is not. Depending on your gear, the ethanol can be condensed and reused when you boil it away to get your CaCl2 back.
If you need something that works on a larger scale (say, to purify a twenty kilo sack of the stuff), and especially if the NaCl is present as a
relatively small percentage of your mixed salt, then I would suggest crystallizing out the NaCl from a saturated solution; it is much less soluble
than CaCl2 and will crystallize out first (alternatively, the CaCl2 will dissolve first, if you start with an excess of the solid). The details would
depend on just how much of your initial mixture was NaCl and how much was CaCl2, as well as the degree of hydration of the CaCl2.
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not_important
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CaCl2 and its hydrates are reasonable soluble in methyl and ethyl alcohols, while NaCl has quite low solubility in the same.
Heat the mixture in a thin layer, or with frequent stirring, in a oven on lowest heat to drive off most of the water. Then crush & powder, put in
a flask, add about twice the weight of alcohol (even 95% EtOH is OK), heat on a waterbath while stirring/swirling so as to have the alcohol simmering.
Put another container into the bath, add a bit of the alcohol, place a funnel + filter paper on top and allow the alcohol fumes to warm the funnel,
then pour the CaCl2-alcohol solution through it. Allow to cool while limiting air access to keep out moisture, and you'll have CaCl2 while the NaCl
is left on the filter.
Reference books on chemical solubilities are available for downloading at the Internet Archive and Google Books, well worth picking up one or two of
them.
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cokezero
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Thanks bbartlog and not_improtant
| Quote: | | Reference books on chemical solubilities are available for downloading at the Internet Archive and Google Books, well worth picking up one or two of
them. |
Just picked one up. Having a handy source of solubilities for a range chemicals will be extremely helpful I feel.
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