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.