Ben Tasker Eagle

Seperating Isopropyl Alcohol and Water

Published: 2020-03-15 10:08:55 +0000
Categories: Misc,

Not really a recipe in the sense of what I normally post here, but it seemed like the best place to file it all the same.

With COVID-19 raging worldwide, vulnerable people in our family, and limited availability (due to others hoarding/panic buying), I wanted to make my own hand sanitiser. Unfortunately, I only had Isopropyl 70% on the shelf, which isn't sufficiently strong once watered down with the other sanitiser ingredients.

This is a technique to seperate the Isopropyl and water from a < 99.9 Isopropyl solution, in order to extract more concentrated alcohol - it's not technically purification as we're not doing anything to the alcohol itself.

Water and alcohols like Isopropyl are miscible - they can be mixed together in all proportions, so there isn't a way to "filter" the alcohol out.

This process is known as "salting out" or dehydrating Isopropyl. Essentially what it's doing is taking a mix of Isopropyl and water (such as you might have in Isopropyl 50% or 70%), and dissolving salt into the water to make brine - the heavier brine will sink to the bottom forming a seperate layer.

Care must be taken with this, Isopropyl is extremely flammable. It can also be absorbed through the skin and poison you.

Preparation Time

Prep: 30 mins
Cooking: mins
Total: 30 mins




  • Wide bottomed Jar and Lid
  • Table Salt
  • Isopropyl Alcohol 70% (or even 50%, you'll just get less)
  • Syringe or turkey baster


  1. Pour a lot of table salt into the bottom of the jar - the aim is to saturate the solution, so you want "too much"
  2. Pour in the Isopropyl
  3. Put the lid on the jar
  4. Shake vigourously until the salt and the isopropyl are well mixed (not all of the salt will dissolve)
  5. Place on a flat surface and leave to stand for 15-30 mins
  6. The mixture should now have seperated into a layer of brine (at the bottom) and a layer of alcohol at the top (the clear layer)
  7. Carefully unscrew the lid (you don't want to knock and cause remixing)
  8. Use the baster/syringe to extract the alcohol
  9. Carefully put into a new container and seal
  10. Handle very *carefully*, it can be inhaled as well as absorbed through the skin, and is extremely flammable


isopropyl, alcohol, dehydrate, salting out,
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