1
$\begingroup$

I wish to obtain pure sodium chloride crystals from ordinary table salt. But all proprietary table salts seem to contain the anti-caking agent sodium ferrocyanide which I should like to remove.

$\endgroup$
3
  • 3
    $\begingroup$ If you're looking for high purity salt, don't buy table salt. Buy it from a chemical supplier, for example: sigmaaldrich.com/catalog/product/sial/… $\endgroup$
    – Zhe
    Sep 6, 2018 at 0:22
  • $\begingroup$ Dissolve and recrystallise. $\endgroup$
    – Karl
    Sep 8, 2018 at 6:56
  • $\begingroup$ And it's supposedly soluble in acteone. Or so wikipedia says. Just wash it out. $\endgroup$
    – Karl
    Sep 8, 2018 at 7:08

2 Answers 2

2
$\begingroup$

Don't. Ferrocyanide is a good way of tying down cyanide ions so they don't do their usual bad things to you. Trying to purify the salt could release the cyanide ions.

$\endgroup$
1
  • $\begingroup$ How should that happen, except by adding strong acids? $\endgroup$
    – Karl
    Sep 8, 2018 at 7:09
1
$\begingroup$

Pass a salt solution (uniodized table salt) through a column packed with an anion exchange resin in the chloride form (e.g. Dowex 1x8). The ferrocyanide ions will be replaced by chloride via mass action. This mild process will not release cyanide, as the ferrocyanide ion is very stable.

At some point during such use, the resin will start to become saturated with ferrocyanide and would have to be regenerated back to the chloride form. This would require chemically pure salt, if course.

I agree with Zhe that it would probably be easier and cheaper to just buy pure reagent grade sodium chloride. But the principle is worth illustrating in case you have a special reason to purify it yourself.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.