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Specialty Chemistry Forums => Citizen Chemist => Topic started by: Viper3k on March 30, 2005, 04:44:41 AM

Title: Separation of Kcl from Nacl
Post by: Viper3k on March 30, 2005, 04:44:41 AM

Hello all, i'm new here and have a question.
Im wondering how i would go about separating potassium chloride (KCl) from sodium chloride (NaCl)
I bought the roughly 50-50 combination at a supermarket as an alternative to normal table salt but i need the potassium chloride for an experiment.
I'm guessing this will be difficult as the two compounds are extremely similar and have had no luck searching the web. I dont have any special lab equipment so i hope i dont need it.

Thankyou all in advance.

Title: Re:Separation of Kcl from Nacl
Post by: AWK on March 30, 2005, 05:05:28 AM

KCl is well soluble in hot water, where us NaCl solubility only slightly depends on temperature.
Treat mixture with a hot water. After cooling the precipitate will contain excess of KCl. After repetition this process for last precipitate a few times you will obtain almost pure KCl even if starting mixture contained a few percent of KCl.

Title: Re:Separation of Kcl from Nacl
Post by: Viper3k on March 30, 2005, 06:16:20 AM

Okay, thanks for the info.

So i presume my method would be getting hot water and disolving as much of the salt mixture as possible then allowing it to cool and a precipitate will form which will be a higher precent of KCl.
Then redisolve this precipitate and repeat and it will be even more pure?

Correct me if im wrong.
Thanks.

Title: Re:Separation of Kcl from Nacl
Post by: AWK on March 30, 2005, 08:05:45 AM

This procedure is called a fractional crystallization

Title: Re:Separation of Kcl from Nacl
Post by: hmx9123 on April 01, 2005, 06:55:10 PM

The other thing to do is to dissolve as much as will dissolve in boiling water, and filter it hot--since the solubility of NaCl is very similar at RT and at 100 deg C, it will precipitate out of solution when boiling (or will not have dissolved to begin with).  That means that your solution has a much higher concentration of KCl than NaCl.  Then you can boil the solution you just filtered some more until more NaCl precipitates out (from water loss due to boiling--you're concentrating the solution).  Reapeat the process until you're happy.

Of course, the easiest way to do this is to go to the supermarket or hardware store and ask for 'non-sodium' water softener tablets.  I bought a 40-lb. bag of pure KCl for about $4 at a supermarket.