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Purifying IPA

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Nathanial.Dread

Nathanial.Dread

Esteemed member
All I can find at my local stores is 70% IPA, however, I have an abundance of homemade sodium carbonate, and since it is not (very) soluble in ethanol, would it be possible to add powder SC to the IPA and use it to dehydrate the solution?

I feel like it would work in theory, but I haven't found anything that definitely says "this will work."

If it doesn't work, could I do a normal IPA reaction with 70% IPA and SC, and then clean it up with an acetone wash later, to remove any SC the IPA may grab? I have plenty of IPA, but not much acetone, and would like to save it for when the volume I need to wash is smaller.


Blessings
~ND
 
Are you in the US? Pretty much every CVS I have ever been to has the 91%.

Anyway, here is a little reading:

Purifying Rubbing Alcohol Into 99% Isopropanol

Epsom salt is magnesium sulfate heptahydrate (MgSO4 * 7H20) but can be converted to anhydrous magnesium sulfate (MgSO4) simply by heating the dry crystals at 100 degrees Celsius for two hours. Once in anhydrous form, magnesium sulfate can be added in excess to the rubbing alcohol where it absorbs the water molecules to form various hydrate crystals.

The mixture of isopropanol and hydrate crystals is then poured over a filter; the collected liquid below is roughly 99 percent pure isopronanol.
Click to expand...


The following is from a paper from 1932... not the simplest method in the world but interesting in my opinion and worth mentioning just for fun:

Absolute isopropanol is easily prepared. The 91% grade is shaken with 10% of its weight of commercial flake sodium hydroxide, separated from the aqueous layer which forms, then shaken with a little more sodium hydroxide, decanted and distilled. The product obtained mixes with eight volumes of carbon disulfide, xylene or petroleum ether without the slightest trace of turbidity.

Dilute isopropanol can be concentrated by shaking with dry sodium chloride. Water is removed as a saturated layer of brine. The upper layer contains about 87% isopropanol and 2-3% of sodium chloride. While distilling, an additional quantity of brine separates. The distillate has so nearly the composition of the 91% azeotropic mixture that it can be used as such without further treatment. Or, after shaking the dilute isopropanol with sodium chloride and separating, it can be treated directly with sodium hydroxide and the absolute grade prepared.
Click to expand...
 
Cool.. it looks like the epson salt is the best way to go.
Not sure about the sodium carbonate, maybe, no idea.

If i may ask a semi-related question.... :?:

Is there a way to remove that poison that is added to denatured alcohol ?
Also, does that poison evaporate with the alcohol.. or does it stay behind?
 
expandaneum said:
just add allot of salt and watch the layers separate. The top layer you want to keep
Click to expand...

i suppose you mean just table salt (or NaOH). Sounds awe+sum, i'll experiment.. Many thanks!
 
Uhmm, i got another related question :| :roll: :roll: :roll: :x :want: :?:

How long does it take (should you shake) to absorb the water, and become anhydrous? :)
 
From Wikipedia:

Isopropyl alcohol is miscible in water, alcohol, ether and chloroform. It will dissolve ethyl cellulose, polyvinyl butyral, many oils, alkaloids, gums and natural resins. It is insoluble in salt solutions. Unlike ethanol or methanol, isopropyl alcohol can be separated from aqueous solutions by adding a salt such as sodium chloride, sodium sulfate, or any of several other inorganic salts, since the alcohol is much less soluble in saline solutions than in salt-free water. The process is colloquially called salting out, and causes concentrated isopropyl alcohol to separate into a distinct layer
Click to expand...

I'm surprised I've never seen this discussed it definitely seems like the easiest way to dry IPA.
 
70% IPA. 30% water.

So now I wonder is it 70% by volume or 70% by weight?

Assuming its volume, I'm sure you could freeze 100ml of 70%, and when decanting you should be left with ~70ml of ~99% IPA
Or if the % is weight you could work that out too but volume is easier.

The reason being is my friend did an ISO chali tek, and tried to dry his IPA first by freezing (there was ice precipped) and decanting, followed by anydrous magnesium sulphate to remove any leftover water.

So couldn't just freezing work? Haha
 
No freezing to separate wont work because the iso and water stay miscible even at low temperatures because they have formed a bond. The freezing temperature of the solution changes but they dont separate.
Excess sodium carbonate does work to dry it out however there is a risk that the sodium carbonate will crystalise around the spice trapping it.
 
It wont dry the iso but will separate it a bit more. Then when you got your more pure iso and you want to use it for fasi you should still dry it with an excess of anhydrous magnesium sulfate.

take care
 
alert said:
From Wikipedia:

Isopropyl alcohol is miscible in water, alcohol, ether and chloroform. It will dissolve ethyl cellulose, polyvinyl butyral, many oils, alkaloids, gums and natural resins. It is insoluble in salt solutions. Unlike ethanol or methanol, isopropyl alcohol can be separated from aqueous solutions by adding a salt such as sodium chloride, sodium sulfate, or any of several other inorganic salts, since the alcohol is much less soluble in saline solutions than in salt-free water. The process is colloquially called salting out, and causes concentrated isopropyl alcohol to separate into a distinct layer
Click to expand...

I'm surprised I've never seen this discussed it definitely seems like the easiest way to dry IPA.
Click to expand...
This works as advertised, and is also a good suggestion. The top layer won't be pure isopropanol, but it would be more concentrated than the one you started with. And the bottom layer will be mostly water, salt and IPA traces

In any respect, it is better to keep an eye on volumes; a 70% IPA is assumed to be 70% IPA and ~30% water (all by volume). A 100% successful salting of 100ml of 70% IPA as described above should, in theory give you 70ml of IPA. If more the IPA ml retrieved, the less the purity, in which latter case further drying with MgSO4 would bring it a few degrees purer.

You will need a hydrometer to measure how pure your IPA is.
 
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