70% Isopropyl Alcohol: Scale Down the WHO Hand Sanitizer Formula

The WHO formula calls for a 75% alcohol content in the final hand sanitizer. In the previous video, we saw that this is not possible using 70% alcohol as an ingredient. (91% Isopropyl Alcohol: Scale Down the...)

The best you can do is to add only hydrogen peroxide and glycerin, and no more water. To get the correct amounts of these ingredients to add, start with the amount of 70% alcohol to use, for example, 300 ml.

Calculate the amount of pure alcohol present. 70% of 300 is 210 ml pure alcohol.

The scaling factor is the amount of pure alcohol you are starting with, divided by the amount of pure alcohol in the original WHO formula. In the original WHO formula, multiply the amounts of the other ingredients by the scaling factor. Add the resulting amounts to your alcohol solution.

Scaling factor:        210 ml   /  7515 ml  =  .0279  

Hydrogen peroxide 3%: 417 ml x  .0279  =  12 ml
Glycerol 98%: 145 ml x  .0279  =    4 ml

The final volume of hand sanitizer is the sum of the three ingredients.

Total solution:   300 + 12 + 4 =   316 ml

The final alcohol strength is the amount of pure alcohol divided by the final volume, or 66% in this example.

Strength: 210/316 = 66%

The final strength must be at least 60% to be effective.

The next video shows how to use ethanol instead of isopropyl alcohol.
Ethanol 180 & 140 Proof: Scale Down t...