Purifying isopropanol

Is anyone using an ethanol proof floating type meter to measure isopropyl? How do you calibrate it? How do get the water out of your isopropyl? Reflux with lime? There’s a Reddit post saying add nacl and decant, does that do it? Or mol seives? 3A, 4A?

Also, is the 91% isopropyl they sell for$10/gallon at Walmart typically contaminated? Wondering if we can purify and use that for extraction, but haven’t taken the time to track down the purity certificates.

They don’t have 55 gallons at Walmart.
I’d just buy 99% gallons online till you need a drum.

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I got from BVV last time like $25 delivered per gal.

Only buying 10 gal at a time now. We’re small time

Do you know how to measure it? Does the float just work on density?

I buy 5 gallons of 99% iso for about 80 shipped. To my door the very next day.


I dont think they can be recalibrated for use with another solvent, even if the solvent you choose is an alcohol they have different densities so using an ethanol meter will give you slightly fucked readings in isopropyl.

Would be easier just buying ethanol proofing mol sieve and using that to remove water whenever you think it’s necesssry.



Found this one, in case anyone else was looking for the same


if you could get some separation, instead of decanting maybe freeze and just pour off the isoproanol from the water layer

I suspect your ethanol proof hydrometer will provide a decent estimate of the isopropanol content. Those two substances have specific gravity whose differences with that of water vary by only 1.5% (0.7893 and 0.786 g/cm^3, respectively, vs about 1.000 for water, at 20 C).

Isopropanol is slightly less dense, so in its pure form it will allow an ethanol proof hydrometer to sink deeper, until it reads about 102%.

The ethanol proof hydrometer I looked at conveniently had two extra graduations above 100%…


Thanks for that, I saw how close the densities were too, and thought it had to be close, but didn’t think to do the math like you did.

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yeah, I was going to argue with @ScoobyDoobie on that basis :wink:

the gauge isn’t lying, it’s just confused by the lack of liquor

prove you’re smatter than the gauge :rofl: :joy: :rofl: