Cheapest way to make up to 99% pure isopropanol

[Beamin]

Normally buying isoprop. there is a rip off because its 50%, too low to be usp and won't disinfect things, and too watery to act as a good solvent. But 50% in a large botles fits their margins. Also the cheapest source even though 50% is water. Buy a bunch of bottles. Next you turn it into 99% by adding a large amount of salt until you see two cm thick layer on the bottom. Shake vigously. settle, an aquous layer will form, decant.
this is making the aqueous fraction super saturated. Once it's super saturated it will pull the water in all the way out of the prop. up to 99%. The fractions will separate like oil and water. You can add more salt to be sure but dont have to.  Add molecular seives or another drying agent like Ca salts, and you have a very easy way to get to complete dryness, with no heat or still. Although compleate dryness is not neccisarry for most things. All for 1/2 the price of buying 91%. You can make the 99% down into 70% for cuts and first aide, or 85% for a good universal solvent/ cleaner/ screen cleaner. Just keep the bottles capped tight as water/humidity will get to them or leave on molecular seives. You could do this with other alcohols too.

[JackJones]

Gasoline de-icers are usually isopropanol. Some of them do have additives in them so you have to check that. The one I use is pure isopropanol with nothing added. 4€/L, can't really beat that.

[Jeroen3]

1 L of 99.85% IPA is €6.15 at the cleaning specialist. And it's not even a product that can be sold freely. (something drugs related)

It must have better availability in countries that don't restrict the substance, right?

[ogden]

Worst thing for cleaning electronics and screens is IPA contaminated with saltwater.

[wasyoungonce]

Thanks Beamin

I find it expensive to get hi quality IPA locally. 


Sent using iPhone

[mariush]

Go to a veterinarian, they'll have 90% and higher alcohol. Another option that's often available is the 70% variety.

See for example https://pipevet.com/alcohol-isopropyl-99-gal
 
In Australia, (random Google search) ... here's 5L 99% for 30$ : https://www.sydneysolvents.com.au/isopropyl-alcohol-ipa-isopropanol-99-5-litre
20 liters for 80$ (and other quantities): https://www.sydneysolvents.com.au/?rf=kw&kw=IsoPropyl+Alcohol+

[Zero999]

You don't want pure isopropanol. Some water is a good thing because it dissolves some salts, which alcohol can't. I don't know what percentage of water is best, but 50% seems reasonable.

[Jeroen3]

You don't want pure isopropanol. Some water is a good thing because it dissolves some salts, which alcohol can't. I don't know what percentage of water is best, but 50% seems reasonable.

This is why flux cleaners are not one solvent.

[MagicSmoker]

You don't want pure isopropanol. Some water is a good thing because it dissolves some salts, which alcohol can't. I don't know what percentage of water is best, but 50% seems reasonable.

Hmm, as individual solvents this is true, but when you add water to IPA all you've really done is make it a worse solvent for both organic substances and salts. If you want to cover all your ionic bases [rimshot!] then it's best to wash first with deionized (not distilled) water then with 99% IPA. The water removes the salts and the 99% IPA removes both the water and any organic residues. Drying over 4a molecular sieves is actually good practice routinely used in clean rooms, fabs or if you live in Florida, where just leaving your bottle of 99% IPA open for a few minutes will suck up enough water to take it to the 91% azeotrope.

[GreyWoolfe]

If you want a little water in you IPA, CVS sells 91% IPA for just a couple of bucks a bottle.  I keep that and the MG Chemicals 99.9%.  I can't be bothered to try to make my own.  However, thanks for posting that. 

[wasyoungonce]

Yeah I use around 10% distilled water added to IPA for PCB wash. It’s just doesn’t dry or wash properly with straight IPA.   But I’d rather be adding to than buying diluted

[lordvader88]

Whats the white residue leftover on PCBs after I use mine which is from a drug store and probably %70 or so ?

[Shock]

Whats the white residue leftover on PCBs after I use mine which is from a drug store and probably %70 or so ?

The salt that Beamin added.

[Ian.M]

Easy enough to check for.  Evaporate a ml or so to dryness on a watch glass, then, if there is significant residue, do a flame test on the residue.    Sodium yellow in a flame test is *SO* obvious - you don't need a fancy platinum wire and high purity hydrochloric acid to clean it - a piece of Nichrome wire cleaned in the flame is plenty good enough.

However the white residue on the board is quite likely to be ionic compounds from the flux, and in that case, you'll have next to nothing on the watch glass to test.

Properly preparing pure dry alcohols is not a good 'kitchen sink' chemistry project - without the correct apparatus with well-fitted joints there's too much risk of fire or explosion and a high probability you'll re-contaminate your product, so if you do have salt (or other sodium compounds) in your IPA change suppliers! 

[Electro Detective]

I sort of gave up on that stuff, due to the sometimes 'mystery residue' milky stain thing, which members here state is salt  and the sometimes longish drying times.

My current fav is non residue electronic contact spray cleaner, either directly sprayed on, or into a container for use with Q-tips, brushes etc. 

I buy any decent stuff that's apparently 'safe to use on -most- plastics' in bulk or on sale.
 
It gets the job done and obliterates gunk, oils and flux etc, dries super fast, and no residue afaict

I use it before and after a large intermittent PCB soldering adventure (prep and post clean) and have had no comebacks or issues ever. 

I use it sparingly/wisely because it ain't cheap   
but won't be going back to salty watered down suss isohol any time soon 

[Beamin]

My point was here in the US we have "dollar stores" that sell big bottles of 50% IPA which is useless but cheap: 50% doesn't disinfect 70% is best for germs, and 91 is better for cleaning but if you need drier you can use the salt method.

If you decant right and throw away a little product because its so cheap the salt residue is almost non existent as nacl isn't really soluble in isoprl.

[ogden]

If you decant right and throw away a little product because its so cheap the salt residue is almost non existent as nacl isn't really soluble in isoprl.

Even if you get unrealistic 99% IPA in result, remaining 1% of impurities is exactly that: nacl solution in water. I would not say it is "almost non existent". Sure you can use such for disinfection, but you better do not use it for cleaning electronics of optics/screens.

[Nerull]

My point was here in the US we have "dollar stores" that sell big bottles of 50% IPA which is useless but cheap: 50% doesn't disinfect 70% is best for germs, and 91 is better for cleaning but if you need drier you can use the salt method.

If you decant right and throw away a little product because its so cheap the salt residue is almost non existent as nacl isn't really soluble in isoprl.

A 50% isopropyl alcohol solution kills Staphylococcus Aureus in less than 10 seconds (pg. 238), yet a 90% solution with a contact time of over two hours is ineffective.

In general if you're depending on effective sterilization you shouldn't be using alcohol. Multiple outbreaks of bloodstream infections have been attributed to use of alcohol as a disinfectant.

[radiolistener]

Buying 99% ethanol also is restricted, because it can be used to produce alcohol which needs license and certificates.
But I found that some medical liquids actually consists clean ethanol (it consists of 95.2% C₂H₆O and the rest is water). These liquids have strange and different names. But actually this is clean ethanol 
So, I'm buy it to clean pcb from flux

[mariush]

Here, a common "sanitary alcohol" is 70% ethanol . The rest is water, Sodium salicylate and methylene blue, to make the alcohol unusable for drinks.

Still some of the very poor people use bread or other techniques to filter the alcohol and drink it.

It's about 1$ for 0.5 liter... regular 90% or better IPA can be bought for less.
 

[TheAmmoniacal]

A cheap source of clean ethanol (96-97%) is bioethanol fuel for lamps.

[ov_darkness]

 I pay about 7.5EUR for 5 liters of 99% IPA. For sth like 12EUR I can buy analytical grade one.

[VE2UM]

IPA = India Pale Ale ?

Sorry, it's hot here today.... Couldn't resist !!!!

[westfw]

The geographical dependencies are ... interesting.

a common "sanitary alcohol" is 70% ethanol.

In the US, the standard seems to be 70% IPA.  I don't know why.

stores that sell big bottles of 50% IPA

I've never seen 50% isopropyl for sale.  The common stuff is 70% ("Rubbing Alcohol"), which sometimes goes on sale for about $1/16oz.

50% doesn't disinfect

Really?  I though whiskey was moderately effective as a disinfectant (at 80 proof or 40%)

Gasoline de-icers are usually isopropanol.

Be careful; in the US, many de-icers are methanol, which is substantially more toxic that IPA.

[99% IPA] is not even a product that can be sold freely. (something drugs related)

I've heard that.   But it's also available at the local grocery store.  I was behind a woman who was buying 4+ bottles once.  She mentioned to the cashier that she worked at a Stanford Bio lab, and it was less of a hassle to get at the grocery than it was to order from their technical suppliers...

[tooki]

The geographical dependencies are ... interesting.

a common "sanitary alcohol" is 70% ethanol.

In the US, the standard seems to be 70% IPA.  I don't know why.

Because 70% is the concentration for optimal effectiveness as a disinfectant. Above this, the alcohol actually coagulates the cell walls of bacteria instead of dissolving them, causing reduced disinfecting action.

Additionally, the water slows down evaporation, which can be useful in disinfecting to make sure there's enough time to dissolve the germs. (Whereas in technical applications, this can be a distinct disadvantage.)