Determining how much %w/w of 96,25% ethanol is needed for an 80% v/v solution


I am trying to figure out how much %w/w of 96,25 ethanol is needed for a sanitizing gel of 80% v/v pure ethanol content. 

My supplier has told me that the specific gravity of the 96,25% ethanol I purchased is 0,8053. 

Hence, I calculate that 80% v/v of pure ethanol corresponds to 83,12% v/v of 96,25% ethanol.

My sanitizer % v/v is:
water 14,81 % v/v
ethanol (96,25%) 83,12% v/v
glycerin  1,45% v/v
carbomer 0,5% w/w
hydrogen peroxide 0,125% v/v

My question is how do I convert % v/v to % w/w?

And then how can I confirm that my calculations are correct?


  • FekherFekher Member, Professional Chemist
    edited June 23
    @Mariaz ; I guess you should add neutralizer for your LOL for the Carbomer  
  • MariaZMariaZ Member
    Thank you for the link. I had seen this link, and it helped me a lot to understand the whole process. I also need help on understanding how the specific gravities are calculated because I have 96,25% ethanol instead of 95%. As ethanol is a controlled commodity in Greece, we need to be exact with how much we use. Can you send me the formulas based on which you found the amount of ethanol needed for the sanitizer? My supplier has given me the specific gravity of 96,25% ethanol to be 0,8053. How do you find how much of this to use in order to obtain a sanitizer with 80% v/v ethanol content? And how do you convert this to % w/w? Then I have to re-convert this to ethanol volume (anhydrous) as this is needed to be kept in our records for customs control.
  • MariaZMariaZ Member
    Can anyone help with this?
  • Cafe33Cafe33 Member
    You are asking simple density, mass and volume questions. Please do not take this the wrong way but you really need to read a few chapter in a chemistry book before you proceed.  

    Everything in your formula should be by weight. So calculate what volume of alcohol you need and convert it to mass. Also, you are missing a base to neutralize your carbomer. 
  • MapXMapX Member
    @MariaZ You can search Alcoholometric Tablet in US Pharmacopoeia for your calculation.

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