Sciencemadness Discussion Board - Sodium chloride - does it have hydrate forms?

Sodium chloride - does it have hydrate forms?

RogueRose - 8-3-2017 at 10:04

In the last couple months I've read in a few places (maybe some other forums) that people were using "anhydrous" NaCl that they had dried. They were using this to remove water from stuff like alcohol or possibly something like ethyl acetate or acetone. I don't remember exactly what was to be dried but the goal was to remove water from a liquid in at least 2 applications. Another application was to use it to dry gases.

I know NaCl attracts water which is why people put rice into salt but I've never seen the salt listed as having water attached to the compound, in any form. I've seen some listings in google when I searched hydrates of NaCl but the sources were always some strange chemical company or an ACS journal entry which the clip was dubious as to whether it was truly referring to hydrated NaCl.

When I did find it it always references a 1:1 monohydrate. It seemed to always state the 1:1 which I've never seen used when referring to other hydrates of other salts or any molecule.

Can anyone shed light on this and possibly give reasons to use this over something else if it can be used for drying? At what temp does it loose it's water molecule if it indeed does have one?

Tsjerk - 8-3-2017 at 11:44

I read it as well, but NaCl doesn't form hydrates. It also doesn't attract water, rice in salt is there to capture water, but that doesn't mean it attracts it. It is not hygroscopic. It doesn't work to dry liquids.

Magnesium sulfate forms a monohydrate, as many compounds.

Elemental Phosphorus - 8-3-2017 at 12:20

I am guilty of this as a matter of fact. I said 'anhydrous NaCl' meaning I heated it in an oven in hopes of driving any water off. However, Nile Red uses a saturated sodium chloride solution to try and remove water from a solution in some videos, so maybe it does work.

DraconicAcid - 8-3-2017 at 12:28

Quote: Originally posted by Elemental Phosphorus

I am guilty of this as a matter of fact. I said 'anhydrous NaCl' meaning I heated it in an oven in hopes of driving any water off. However, Nile Red uses a saturated sodium chloride solution to try and remove water from a solution in some videos, so maybe it does work.

Any saturated solution will absorb water- that's how osmosis works.

Dmishin - 9-3-2017 at 04:06

There is dihydrate NaCl*2H2O, but it only exists near 0C.

cryst3.jpg - 17kB

RogueRose - 9-3-2017 at 10:32

Thanks - all this is interesting. I know the examples I read (not on this forum though, I think on Chemicalforums and some other postings) that they used it as if it would form the monohydrate by passing gas/air over it. I see where the dihydrate listed

I had looked for hydrates on the Wiki page and it wasn't there when I looked so I checked the revisions. It looks like it was added almost a month ago exactly, about the time I started reading that in some places and searching for it, but not dihydrate, just hydrated (I only knew of a suspected monohydrate at the time)
Here is the revision page - look at Feb 9 2017

Here is a monohydrate listed on chem spider as a "1:1:2"
http://www.chemspider.com/Chemical-Structure.11248334.html

So this looks like it might be useful in de watering liquids that are still liquid at 30F. I'm not seeing exactly how it would work buy my mind thinks it might. Add the salt to say IPA/water and freeze. at 30F the salt will crash out more than it would above that temp, is that correct? Filter off crystals and repeat? Does that make sense? Is that how it would work?

On a side note, looking at the revisions of these Wiki pages is eyeopening. it shows how many people actually edit these pages and how much control a few people have. One poster has thousands and thousands of edits on mostly chemical entries. I wonder if people like that get paid for their work?

NEMO-Chemistry - 10-3-2017 at 20:33

http://chemicals.etacude.com/s/sodium_chloride.php