Member
I have a distributor sending me a couple of barrels of pre-made WHO formula liquid sanitizer. It's 80% ethynol. I normally just add a gelling agent to it at .5%, and fill it into containers. This time around my client is asking me to turn some of it into surface cleaner by bringing the Ethynol down to 30%. I'm struggling with the math on how to calculate that properly and whether or not it's ok to just add more distilled water. I'd really appreciate the help. Thanks
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• Member, PCF student
You can think about it like this:
If the supplied sanitizer is 80% ethanol, then 1 litre contains 800mL.
You want to add water to make a 30% solution.
A 30% solution means 300mL of ethanol and 700mL of water.
(1) calculate the required amount of sanitizer to get 300mL of ethanol. You can see that 1mL of ethanol would be 1000mL (sanitizer) / 800, or 1.25mL.
(2) You need 300mL of alcohol, so that is 300 x 1.25mL of sanitizer or 375mL of sanitizer. The rest is water, or 625mL. (for each litre of 30% alcohol v/v)
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• Member
@Belassi Thank you so much for your reply. This is incredibly helpful. I've read so many confusing things.  I assume the same can be said for the hydrogen peroxide and glycerin etc?
• Member, PCF student
Yes, exactly. This is the way I teach my GMAT students to understand questions involving the calculation of mixtures.
Cosmetic Brand Creation. Concept to name to IMPI search to logo and brand registration. In-house graphic design inc. Pantone specs. Cosmetic label and box design & graphics.

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