Cheapest way to make up to 99% pure isopropanol

[tooki]

By the way, this article from HP (copied from one of several recent flux cleaning threads) says on p.11 that the optimal concentration of IPA for flux removal is 80%, because some of the activators in flux are soluble in water, but not alcohol, and so ~100% solvent will not produce optimal cleaning. As such, this entire exercise in raising the concentration is likely completely in vain.

http://hparchive.com/Bench_Briefs/HP-Bench-Briefs-1982-07-10.pdf

[magic]

It could probably be distilled without a trace of salt but why bother when 99% is available off the shelf.

By the way, this article from HP (copied from one of several recent flux cleaning threads) says on p.11 that the optimal concentration of IPA for flux removal is 80%, because some of the activators in flux are soluble in water, but not alcohol, and so ~100% solvent will not produce optimal cleaning. As such, this entire exercise in raising the concentration is likely completely in vain.

http://hparchive.com/Bench_Briefs/HP-Bench-Briefs-1982-07-10.pdf

Good to know. Cleaning rosin flux with pure IPA always leaves a bit of white residue. I'll try with some deionized water added next time.

[Ian.M]

By the way, this article from HP (copied from one of several recent flux cleaning threads) says on p.11 that the optimal concentration of IPA for flux removal is 80%, because some of the activators in flux are soluble in water, but not alcohol, and so ~100% solvent will not produce optimal cleaning. As such, this entire exercise in raising the concentration is likely completely in vain.

http://hparchive.com/Bench_Briefs/HP-Bench-Briefs-1982-07-10.pdf

Good to know. Cleaning rosin flux with pure IPA always leaves a bit of white residue. I'll try with some deionized water added next time.

In the other recent IPA topic: https://www.eevblog.com/forum/projects/drying-ipa-with-silica-gel-will-this-work/msg2522505/#msg2522505
I posted a link to an IPA concentration vs density (specific gravity) table.    80% IPA by volume would be a density of 0.85 g/ml @20 deg C.   Due to IPA's tendency to adsorb atmospheric moisture, if your stock bottle is getting low, or you suspect it has been poorly sealed, I would strongly recommend weighing a known volume to check its density *before* dilution.

[Brumby]

To date, I've been getting the 2 litre IPA from Altronics which costs $26.95 and I have to drive more than half an hour to get it or pay for shipping.  I've never been able to work out what % it is, but it seems to work OK for me.

What I have recently found is a supplier in Sydney who offers 5 litres of 100%, 99% or 70% IPA delivered to my door the next day for $29.50 - or I can go for a 25 minute drive and pick it up (for the same price).  They also have other sizes including a 200 litre drum of 100% (but that's a bit much for me to handle).

I haven't ordered any, so I don't know if there are any hoops to jump through, but I'm not expecting anything too onerous if there are.

[westfw]

I don't know why.

Because 70% is the concentration for optimal effectiveness

I meant "why Isopropyl in the US and Ethanol elsewhere."

[tooki]

Oh, gotcha. Probably because it's legally so much easier to deal with, since it's not drinkable.

That said, here in Switzerland, for example, both seem to get used (medically) about equally often (purely by my own observation, no hard stats).

What I have discovered, for cleaning purposes, is that high-proof ethanol is available at the grocery store, sold as fondue pot fuel, which is very cheap, and whatever it's denatured with is not Bitrex, which can't be allowed anywhere near food for obvious reasons. It does leave some residue when dry, so it's not ideal as a final rinse, but it works eminently well enough for the bulk. (So I just use technical IPA or bona fide flux remover for that.)

[vealmike]

Ah, now I understand the whole Tequila thing. Well, OK 2/3rds of it. What does the lime wedge do?

[fixit7]

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.

As an experienced chemist, I can offer you some tips on IPA.

Your post is not clear about what you are looking for.

I can tell you that 91% IPA is an excellent disinfectant.

The reason is behind the mode of action of 70% IPA. Bacterial cells have proteins in their cell wall and when this protein comes in contact with the 70% IPA during disinfectant application, coagulation of proteins takes places in which denaturation of proteins occurred and after that IPA penetrate in the interior of the cell which cause lysis or death of the cell. Protein coagulation also happens in case of 100% IPA but with very fast rate and because of this very fast protein coagulation process denatured protein forms protective layer out side of the cell. When this happens, 100% can not penetrate inside the cell and not able to kill the microbe. Microorganisms become dormant in that conditions. In case of 70% IPA protein coagulation takes place with a slow rate and due to this 70% IPA get enough time to penetrate in the cell and kill the microorganism. Another factor is contact time, 70% IPA takes longer time to evaporate from any surface hence get enough contact time and in this mean time it show its efficacy but in case of 100% IPA, evaporation will be very fast, contact time will be less and it will not be so effective against microbes. That's why 70% IPA solution is used as disinfectant in pharmaceuticals industries.

Good luck in your quest.

[Beamin]

IPA = India Pale Ale ?

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

I always think that. Harpoon IPA out of new England is the best for cleaning off flux so is their hefeweizen UFO "unfiltered offering" is the best bear ever.

I guess this varies wildly depending on the way your country taxes ethyl alcohol or converts crude oil into alcohol like in the case of IPA. I'm also surprised that so many people here just think of using it for cleaning flux. I always leave the flux for the most part and use alcohol for cleaning and disinfecting. You can also use it to make hash oil as I did as a kid. Funniest use is taking a 5 gal water jug, rising with IPA then touch a match to the top as it makes a huge roaring sound and huge flame and scares the hell out of people then makes a pop sound(either the bottle self extinguishing or the sound from people pants)

Mmmm filtering blue denatured alcohol through a slice of bread so you can drink it. That's what the most classy of wine snobs do, after they go blind and get cirrhosis and/or wet brain.


The denatured ethanol around here smells like they put acetone in it.

[KaneTW]

Denatured alcohol usually includes 2-butanone nowadays. The butanone causes the acetone-y smell.

[macboy]

Here in Canada, I buy 99% IPA at Costco. Last time it was $9.99 for four 500 mL bottles ($10 / 2 liters), but I think the price is up to around $12 now. Still super cheap and super easy. 

[Cliff Matthews]

Here in Canada, I buy 99% IPA at Costco. Last time it was $9.99 for four 500 mL bottles ($10 / 2 liters), but I think the price is up to around $12 now. Still super cheap and super easy.

Thanks, my friend is a member. Walmart wants 6.99 CDN / 500ml and it must be ordered (18+ 'over the counter').

[rcbuck]

I buy 32 oz 91% Isopropyl Alcohol at Wally World for $2.50. I buy it for disinfectant purposes but also use it for cleaning PCBs.

[Beamin]

I buy 32 oz 91% Isopropyl Alcohol at Wally World for $2.50. I buy it for disinfectant purposes but also use it for cleaning PCBs.

91% isn't nearly as good as 70% which kills 99.99% of germs vs about 70% killed, for the 91%. The alcohol has to get into the cells so that's why less is better. The peptoglycan wall of the bacteria is not oil or alcohol soluble so only that 9% alcohol with 5% water gets in. Also remember the bacteria doesn't die until full dryness.

[Smoky]

This stuff works very well. I bought it on Ebay. It's $8 for one gallon, you get four quarts. $12 to ship

It works very well and leaves no residue.



But most of the cleaning I do when soldering is Dupont 105 lacquer thinner. I have a five gallon can in the garage!

[Nusa]

This stuff works very well. I bought it on Ebay. It's $8 for one gallon, you get four quarts. $12 to ship

It works very well and leaves no residue.

(Attachment Link)

But most of the cleaning I do when soldering is Dupont 105 lacquer thinner. I have a five gallon can in the garage!

I agree, it's both easier AND cheaper to buy better qualtiy iso in the first place than to concentrate it yourself.

I looked it up, and Dupont 105 is hazardous stuff. You don't want to be touching or breathing it. So pay attention to protection and ventilation if you use it.

CAS-No. Chemical name Concentration
67-56-1 Methyl alcohol 50%
108-88-3 Toluene 19%
67-64-1 Acetone 15 - 26%
1330-20-7 Xylene 8%
100-41-4 Ethylbenzene 2.0%
8032-32-4 Vm&p naphtha 1 - 4%

[Beamin]

This stuff works very well. I bought it on Ebay. It's $8 for one gallon, you get four quarts. $12 to ship

It works very well and leaves no residue.

(Attachment Link)

But most of the cleaning I do when soldering is Dupont 105 lacquer thinner. I have a five gallon can in the garage!

Is that really dry alcohol? Most is 98% because as soon as you open it the humidity gets into it. Dupont 105: is the 105 for all the different kinds of cancer it gives you?

I just leave the flux on it adds character to my boards.

[Smoky]

I pour a small amount of I-Max in a PPG mixing cup and use a trimmed China bristle brush to clean.

I do the same with the lacquer thinner but I keep that in a squirt bottle.

I've sprayed, Dupont, PPG, Standox, and Sikkens auto refinish products for about 38 years.

While in the Marines, we went through barrels of dry cleaning fluid to clean rifles and machine guns. Why don't you go check that stuff out?

I know what to use in my new electronics hobby.