So I have 1 liter of isopropyl alcohol 99.9% and I would like to make it more effective (make it 70% concentration) and at the same time make it last longer as there's a shortage off this stuff. So I came up with 2 ideas:
1) I can add 400ml of water to it so that it will be 71.4% alcohol solution.
2) I can add 1 liter of 40% vodka to it and that would be 50% isopropyl alcohol + 20% ethanol. => 70% alcohol solution.
Which one is better? Can I combine this two alcohols?
Will that make a solution with 70% alcohol or a 50% isopropyl and 20% ethanol?
Will solution 2) be an effective biocide against viruses?
Disclaimer: My brother asked the same question in Chemistry and I'm trying my luck here.