Sciencemadness Discussion Board

Drying IPA

NEMO-Chemistry - 4-1-2018 at 12:56

I am near the end of my 20ltr drum of IPA, its lasted ages!! When i got it ages ago it was 99.9% pure.

I am sure over the last 18 months it must have some water in it by now, I have about 2.5 ltr left, i want to use this for chloroform making and some other stuff.

I decided I am going to dry it, normally i just salt it out and distill. But i thought i might have a go at salting it then boiling with magnesium chips to dry it. Then distill.

I have used magnesium chips with other Alcs before, is it pretty much the same with IPA?

Sorry for all the questions, i am adding loads of experiments and stuff to my site. I will post all the experiments up here as well

MrHomeScientist - 4-1-2018 at 13:13

I used the method quoted in the 5th post in this thread to prepare absolute IPA from the 91% store-bought grade with good results. I'll copy the relevant part here:
Quote: Originally posted by leu  
JACS 54 1445 (1932)

Note on the Preparation of Absolute Isopropanol
BY LEWIS E. GILSON
During several years of biochemical research the writer has found many instances where isopropanol could be substituted for ethanol in laboratory work. It is cheap and there are no restrictions governing its use; nor is it likely to be an object of theft. The commercial 91% azeotropic mixture was used instead of 95% ethanol and found to be fully equal or superior to the latter as a solvent or extracting medium. Absolute isopropanol was used in place of absolute ethanol.

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.

:cool:


I also discovered that the distillation step isn't optional! I tried using it straight from the sep funnel and got strange results, so I distilled it as directed and there was a surprisingly large amount of NaOH still dissolved in the alcohol.

ninhydric1 - 4-1-2018 at 13:59

Couldn't you wash it with sulfuric acid after the sodium hydroxide phase separation? It seems like sodium sulfate is relatively insoluble in IPA. Or maybe isopropyl sulfate would be formed in large quantities, which would result in another separation problem, huh.

DraconicAcid - 4-1-2018 at 14:08

I suspect you'd have significant quantities of sulphuric acid remaining dissolved in the alcohol.

PirateDocBrown - 4-1-2018 at 14:31

My go-to back in the day would have been CaH2. Since that's much harder to find for the home lab, I'd go with a sulfate.

Na2SO4, CaSO4, or MgSO4.

But the NaOH method sounds very viable!

NEMO-Chemistry - 4-1-2018 at 14:52

Thx for that. I make soap so buy sodium Hydroxide prills in 25kG bags, its alot cheaper like that. I always have plenty of it about.

The above also explains why when i make chloroform, i always get a layer of IPA at the top! But i much prefer chloroform making with IPA to acetone. I will stick some on a test tube and add chloride, this should give me an idea how much water is in it. Then i can decide to go Hydroxide straight away or salt it out first.

I am also going to dry my Methanol, it says 99% but i have never come across that before. Since they over sent me 20ltr methanol (i got it free!), i will use that as my general solvent for a while :D.

aga - 4-1-2018 at 15:00

Still with the Soap ?
Sheeh !
Move on to the Applied Saponifications already.

NEMO-Chemistry - 4-1-2018 at 15:15

Quote: Originally posted by aga  
Still with the Soap ?
Sheeh !
Move on to the Applied Saponifications already.


Soap is relaxing to make.....I made a massive amount the other week! OK i was making Bio Diesel but somehow it all went wrong and I got a emulsion of soap! I shouldnt be so fucking cheap and use potassium hydroxide instead of Sodium hydroxide. But the price of it has shot up lately.

Bio Diesel is being priced out the market at the moment, waste oils and the methanol, let alone the Hydroxides are getting so expensive that bio Diesel is getting as pricey as normal fuel!

I want to have a go at Bio fuel and see how good a solvent it is, its not as flammable as petrol which always makes me twitch when i distill it!

I cheat now, i leave the petrol cap off for a bit before I distill, that way I dont get the really low boiling point stuff.

ninhydric1 - 4-1-2018 at 17:38

You get sent 20 L of methanol for free?! What company does that?

NEMO-Chemistry - 4-1-2018 at 18:52

Quote: Originally posted by ninhydric1  
You get sent 20 L of methanol for free?! What company does that?

A stupid one.

I normally order dolvents in bulk from them, this time I ordered and paid for 2 ltr. But 20 ltr turned up, so i call them and explain i ordered 2 ltr and asked what they wanted me to do about sending it back.

Turns out it costs them more, and is more hassle to ship back at there expense than let me keep it. What was really funny was a week later 2 ltr turns up :D. So i actually paid for 2 ltrs and got 22.

But I am a good customer and now I am even happier, although most people seem to be having problems with them, i think they wont be around much longer.

Which means the bastard of all companies is going to end up dominating!

zed - 9-1-2018 at 14:39

Depends on what you consider dry. If that isopropylalcohol needs to be really really dry, treatment with MgMethoxide would probably do the trick.

Isopropylalcohol itself may react sluggishly with Mg, requiring a reflux to get the reaction started. Though, I suppose the reaction, once started, should eat up any water present.

Swan Brand, 99% Isopropylalcohol, is available at my local Fred Meyer store, for about $3.00-$4.00 U.S. / liter. Not bad!

NEMO-Chemistry - 9-1-2018 at 14:58

Quote: Originally posted by zed  
Depends on what you consider dry. If that isopropylalcohol needs to be really really dry, treatment with MgMethoxide would probably do the trick.

Isopropylalcohol itself may react sluggishly with Mg, requiring a reflux to get the reaction started. Though, I suppose the reaction, once started, should eat up any water present.

Swan Brand, 99% Isopropylalcohol, is available at my local Fred Meyer store, for about $3.00-$4.00 U.S. / liter. Not bad!


Thats alot cheaper than here now!

NEMO-Chemistry - 9-1-2018 at 17:35

Quote: Originally posted by zed  
Depends on what you consider dry. If that isopropylalcohol needs to be really really dry, treatment with MgMethoxide would probably do the trick.

Isopropylalcohol itself may react sluggishly with Mg, requiring a reflux to get the reaction started. Though, I suppose the reaction, once started, should eat up any water present.

Swan Brand, 99% Isopropylalcohol, is available at my local Fred Meyer store, for about $3.00-$4.00 U.S. / liter. Not bad!

ninhydric1 - 9-1-2018 at 18:47

My local pharmacy sells 99% isopropanol as rubbing alcohol for $2 in a standard rubbing alcohol container, but the pharmacies near you probably won't offer it. Do you have access to iso-HEET (or a similar variant of it)? IIRC iso-HEET is also 99% isopropanol.

NEMO-Chemistry - 10-1-2018 at 03:34

Quote: Originally posted by ninhydric1  
My local pharmacy sells 99% isopropanol as rubbing alcohol for $2 in a standard rubbing alcohol container, but the pharmacies near you probably won't offer it. Do you have access to iso-HEET (or a similar variant of it)? IIRC iso-HEET is also 99% isopropanol.


No, i can get 20ltr for around £45 at the moment, delivery is the main problem here as I am not near a major center!