Sciencemadness Discussion Board - Purifying Sodium Chloride

Purifying Sodium Chloride

DFliyerz - 2-4-2015 at 08:18

I have some uniodized sodium chloride that I want to purify, but do to it's flat solubility curve I can't just recrystallize it like most other salts. How do I do this?

papaya - 2-4-2015 at 08:38

Once I was called ignorant asking this same question on this board...

Amos - 2-4-2015 at 09:03

What is the source of your salt? And what do you intend to use it for?

Granulated table salt is usually astoundingly pure aside from a small amount of anti-caking agent which really isn't going to matter with most things you do.

DFliyerz - 2-4-2015 at 09:09

Quote: Originally posted by Amos

What is the source of your salt? And what do you intend to use it for?

Granulated table salt is usually astoundingly pure aside from a small amount of anti-caking agent which really isn't going to matter with most things you do.

A decent-sized container of Morton Uniodized Table Salt, and my main intention is to use it to make a saturated sodium chloride solution for solvent washing, and then I'll undoubtedly use it for other things as well.

Molecular Manipulations - 2-4-2015 at 09:17

Starting from iodized salt, what I do is add a little water to make a slurry, filter as much water off as possible, and rinse a few times, this gets rid of most of the iodide ion. Then saturate some water with the purified slurry, and filter of insoluble anti-caking agents. Now boil the solution until most of the water's gone and filter the salt crystals.
Since you're starting with uniodized salt, you can skip the first step.

[Edited on 2-4-2015 by Molecular Manipulations]

Amos - 2-4-2015 at 14:52

The only anti-caking agent he's going to find in there is sodium ferrocyanide, which is soluble. Personally I wouldn't bother doing anything to the salt. If you're using saturated sodium chloride to wash organic phases, you're not going to get polar, highly water-soluble compounds like potassium iodide or sodium ferrocyanide migrating into layers of solvents in which they are NOT soluble when they're already at such negligible concentration in the aqueous phase. You two are both overthinking it a bit.

Texium - 2-4-2015 at 15:19

Look for Morton canning and pickling salt. It isn't iodized, and doesn't contain any anti-caking agents either. Simply 100% sodium chloride.

Molecular Manipulations - 2-4-2015 at 15:24

Depends on where he gets it. Calcium silicate and silicon dioxide are also used sometimes.
While searching for this, I found this treasure chest of psudoscience passing for "health information":http://www.onlineholistichealth.com/truth-sea-salt/

Quote:

Table salt, which once came from the ocean, but has been stripped of all nutrition, now contains processed sodium chloride fortified with synthetic iodine, anti-caking food additives, and cyanide. Sea salt, on the other hand, also comes from the ocean, but remains whole and intact with over 50 trace minerals including natural occuring iodine.

Not necessarily any lies in that, but thinking there's a difference in synthetic iodine and iodine from the ocean... And didn't we have a discussion on the toxicity of sodium ferrocyanide in salt recently?

j_sum1 - 2-4-2015 at 18:01

I have an almost passionate dislike for these kinds of claims. There is so much muddled information and disinformation in there. Much of which is a confusion of terminology.

Any case of toxicity of any kind is contingent on (a) the specific form of the supposed chemical, (b) the pathway that it may enter the body, (c) the amount involved, (d) the period of the exposure and (e) the presence of other bioactive chemicals that may either enhance or diminish the effect of the chemical in question.

Anything that is properly studied also has (f) the mechanism by which the chemical in question affects the body.

The exact same list of considerations must be made for any claimed health benefits.

Any discussion of the dangers or benefits of any food item that does not address these six things is scientifically deficient and should be either dismissed as quackery or submitted for further systematic study.

That at least is my assessment of the situation.
J.

Etaoin Shrdlu - 2-4-2015 at 19:02

Damn, synthetic iodine?

Funny how cyanide is bad for you only when complexed with iron so it's not biologically available. Natural organic compounds that can actually poison you are just fan-fucking-tastic.

EDIT: And she actually promotes laetrile...doesn't she know that's synthetic?

[Edited on 4-3-2015 by Etaoin Shrdlu]

Texium - 2-4-2015 at 19:03

Ugh, it's quite frustrating indeed. I saw another site that bemoaned the lack of an organic certification for sea salt, because they didn't seem to understand that sea salt is fundamentally inorganic!

Check out the comment section on there. Her self-delusion and super pseudoscience triples when faced with reasonable people who describe in detail what happens to ferrocyanide in the body and how synthetic and natural are identical.

Quote:

Regarding “synthetic” vs “natural occurring”, though on paper a synthetic version may appear to be identical, there is something fundamentally lacking. Just from a logical stand point, how can we expect humanity, organic beings, to flourish consuming synthetically made drugs, food additives, food (GMOs), and even supplements?

She also has the nerve to say that as a so-called holistic doctor of chriropractic health, she has "far more training in nutrition than medical doctors." She definitely likes using excessive quotes to discredit the actual "experts" and "doctors."
I'd comment on that page too, but clearly others have made the majority of points that I would have. No need to be redundant.

Edit: Dear lord... checked some other articles on that same website... enjoy...
http://www.onlineholistichealth.com/afraid-calcium-supplemen...
http://www.onlineholistichealth.com/fluoride-linked-coronary...
http://www.onlineholistichealth.com/natural-isnt-always-natu...

[Edited on 4-3-2015 by zts16]

Etaoin Shrdlu - 2-4-2015 at 19:26

Quote:

Using calcium carbonate (oxide) as the carrier is like trying to drive a bus into the cell. It just can’t happen because the oxide carrier is too big. Thus, there is little to no calcium absorbed. In fact it is like swallowing chalk.

Using calcium citrate as the carrier is a bit better. This is more like trying to drive a car into the cell.

Yes, that's, umm, that's exactly how it works.

j_sum1 - 2-4-2015 at 19:29

http://www.onlineholistichealth.com/afraid-calcium-supplemen...

Oh dear.
Someone please tell this woman about solubility.

nezza - 3-4-2015 at 00:07

One classic method is to make a saturated solution of salt and then pass HCl into it. This precipitates chloride ion by common ion effect and as sodium is the major metal ion there it is pure sodium chloride which precipitates out. This can then be washed and dried.

j_sum1 - 3-4-2015 at 01:53

Quote: Originally posted by nezza

One classic method is to make a saturated solution of salt and then pass HCl into it. This precipitates chloride ion by common ion effect and as sodium is the major metal ion there it is pure sodium chloride which precipitates out. This can then be washed and dried.

That's clever. However, in this particular case it is likely that the NaCl has greater purity than many available sources of HCl. That might complicate things bit.

gardul - 3-4-2015 at 02:12

Quote: Originally posted by Etaoin Shrdlu

Quote:

Yes, that's, umm, that's exactly how it works.

I want to punch a wall now. You got to this before I did. I almost posted one of my not so corherent rants..blah...

careysub - 3-4-2015 at 06:38

Quote: Originally posted by DFliyerz

I have some uniodized sodium chloride that I want to purify, but do to it's flat solubility curve I can't just recrystallize it like most other salts. How do I do this?

The upper range for salt additives is 0.01% for KI, 0.01% for sodium ferrocyanide, and for silicate anti-caking agents (calcium silicate, magnesium silicate, calcium aluminum silicate) it seems to be 0.75% but usually lower (0.25-0.5%).

So the purity of ordinary table salt, even the iodized version, is 99.25 - 99.75%.

On the other hand, according to Sigma-Aldrich:
Sodium Chloride ACS reagent is ≥99.0%

So ordinary table salt (even iodized table salt) qualifies as ACS reagent grade it would seem.

The silicates are usually listed as "insoluble", but might be soluble at the level of 100 ppm or so (depending on which one it is), so if you make a saturated salt solution (360 g/L) you should be able to drive the silicate content down to 0.1/360 = 0.0003 -> 0.03% or so and get 99.97% pure salt (except possible for traces of potassium or magnesium chlorides from the original mineral source).

You would need good analytical equipment to detect the other ion species.

DFliyerz - 3-4-2015 at 06:53

So, the conclusion is that just dissolving and filtering the salt should make it pure enough for most uses?

blogfast25 - 3-4-2015 at 07:51

Quote: Originally posted by j_sum1

Quote: Originally posted by nezza

That's clever. However, in this particular case it is likely that the NaCl has greater purity than many available sources of HCl. That might complicate things bit.

Ideally, HCl gas is passed through a saturated solution of NaCl, to HCl saturation. Since as most HCl prepared from simple generators is quite pure, the precipitated NaCl will also be quite pure.

But it's quite a cumbersome way of purifying salt!

Other chlorides on which this HCl gassing trick works are AlCl3 (hexahydrate), zirconyl chloride and potassium or ammonium hexachlorostannates.

Molecular Manipulations - 4-4-2015 at 05:11

Quote: Originally posted by j_sum1

http://www.onlineholistichealth.com/afraid-calcium-supplemen...

Oh dear.
Someone please tell this woman about solubility.

Quote:

What we hope to absorb when we take a calcium supplement is the elemental calcium. Calcium, being a mineral, as with all minerals, in order to get the amount needed by the body the mineral must be accompanied by a “carrier” or “mineral transporter”. In other words the mineral, calcium in this case, is “escorted into the cells” by a carrier such as carbonate, citrate, aspartate, or orotate (among others).

careysub - 4-4-2015 at 08:30

Quote: Originally posted by DFliyerz

So, the conclusion is that just dissolving and filtering the salt should make it pure enough for most uses?

Yes, and I wouldn't bother with filtering. Just decant the upper layers - salt is cheap.

careysub - 4-4-2015 at 08:45

Quote: Originally posted by DFliyerz

So, the conclusion is that just dissolving and filtering the salt should make it pure enough for most uses?

Yes, and I wouldn't bother with filtering. Just decant the upper layers - salt is cheap.

Also, it is useful to note that two of the salt processing systems used by Morton Salt, and others, is to do exactly this. They create a saturated brine, and decant off the upper brine layer, in a continuous process (usually).

It doesn't seem that this will remove calcium or magnesium chlorides though, which are more soluble.

How does that work in ocean salt pan making?

TonyZ - 10-6-2015 at 12:25

For the purposes of brining, it can be used as is. However, if the application demands it, you can dissolve the NaCl in water. Place an excess of NaCl in water and bring to a rolling boil. Microwave in PP container or Pyrex measuring cup works. Filter. Store in container.

Further processing or purification is unnecessary. However, if you wanted to learn or experiment with anti-solvent crystallization, this could be an viable opportunity. Since temperature has no considerable effect on its solubility and the solute is not sensitive to higher temperatures, you can try antisolvent crystallization.

Add ethanol to the brine solution. This will cause the NaCl to come out of solution. At first there was a saturated solution of water-NaCl. By gradual addition of ethanol, the solubility of NaCl decrease. The behavior of the antisolvent crystallization will be influenced by operating parameters of the process, such as temperatures, agitation, nucleation, etc... There are plenty of references to the behavior of anti-solvent crystallization from Sodium Chloride aqueous systems. Too many to reference.

As an add-on learning experience, one can also distill the left over system to recover the solvent.

You can also make NaCl via vapor diffusion of HCl. The method was adapted from a similar method published previously(Joy et al., 1973). You can read of the method here -http://www.cell.com/cms/attachment/2021776491/2041651718/mmc1.pdf

Enjoy

[edited for formating issues and added the sentence about an "add-on learning experience"]

[Edited on 10-6-2015 by TonyZ]