darkflame89
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Separation of two soluble salts
In a solution where there are 2 soluble salts, is there anyway to separate the two salts? Lets say that i want to separate copper sulphate and
magnesium ethanoate, how can i go about in doing it?
Ignis ubique latet, naturam amplectitur omnem.
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Tacho
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I sugest you check the solubilities. If they are substantially diferent, evaporate part of the solvent, let it cool, the least soluble will
crystalize. Repeat until the second salt starts to crystallize.
The name of procedure similar to what you want is "recrystallization".
[Edited on 22-3-2004 by Tacho]
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thunderfvck
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You can also evaporate the solvent and seperate the solids
by eye.
Microscope may be needed, along with tiny tweezers.
[Edited on 22-3-2004 by thunderfvck]
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Hermes_Trismegistus
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chromatography.
the larger molecular salt will elute from the column sooner.
This will require a bit of trial and error, but remember that it's only the first time you have to do find the fractions.
basically, chromatography consists of packing a glass tube with powdered media (that doesn't dissolve in the solvent) and running a sample of
solvent loaded with the salts through the wet(with the chosen solvent) media.
Collecting many small amounts of the solvent coming off the bottom of the column you'll eventually find the salts you wanted to seperate coming
out in different layers. (you'll have to dry the solvent to find the salts).
the most commonly used media's today are polyacrilimide gels and agarose.(however they are expensive and specialised.
you'll probably want to use cheaper media's like..(in order of decreasing "activity" (holding power)
alumina
charcoal
magnesia
silica gel
lime
magnesium carbonate
calcium carbonate
sodium carbonate
talc
powdered sugar
the solvents that are easiest to procure(old timey) are presented in order of increasing activity (drawing power)
petroleum ether
carbon tetrachloride
carbon disulfide
ether
acetone
benzene
methyl/ethyl alchohol
water
organic acids
aqueous solutions of acids or bases.
the normal ratio of column size is ten times the length to width.
remember to take the collected fractions in small enough quantities to know which salt is which.
Once you gain experience in this technique, you'll love it! It's really easy!
a more cogent explanation of basic chromatography can be pretty easily found on the web.
Arguing on the internet is like running in the special olympics; even if you win: you\'re still retarded.
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BromicAcid
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Separating two salts.... a problem every chemist must face. Usually solubility differences is the way to go. Either evaporate significant amounts of
solvent and see what crystallizes out, evaporate all solvent then try and specifically dissolve one salt out of the cake leaving the other, or adding
another liquid or solid to the mix to depress the solubility of one salt, e.g., acidifying drops out some salts or think of some explosive mixtures
where you dump it in water and it all crystallizes out.
Of course the problem comes in the fact that there are not extensive solubility tables for many solvents other then water. Other separation methods
would fall into making one of the salts, say one you don't want, into a different salt to precipitate it, e.g., for some reason you don't
want silver nitrate, add HCl precipitate the Silver chloride, the HNO3 produced can be evaporated off. Other mechanical separation techniques would
include evaporating the solvent then subliming/distilling off one of the salts, usually the earlier is easiest, especially with some ammonium salts.
There are many other ways, osmosis membranes, ion resin exchange systems, and such but basically your only methods like in solubility differences,
making solubility differences, or mechanical separation. On the topic of your specific example, I would have to know what your solvent is
And or course collum chromatography like Hermes just said above.
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unionised
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This is probably cheating but..
Add excess dilute sulphuric and distill off the ethanoic acid.
Add excess ammonia to the mixed solution of Mg and Cu sulphate.
Filter off the Mg(OH)2 and add it to the ethanoic acid you distilled off earlier.
Add excess sulphuric acid to the solution,dry it down and heat it to sublime off the ammonium sulphate. That will give you a mixture of Cu as its
oxide (by hydrolysis) and sulphate. Add Dilute sulphuric to disolve this residue and then evaporate off the water gently to give copper sulphate.
Chromatography or crystalisation won't always work properly you might well find that what you get is copper ethanoate and magnesium sulphate.
The ions don't remember what salt they were part of before they were disolved in water.
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