How much pure acid should be mixed with 2 gallons of a 50% acid solution in order to get an 80% acid solution?
You should add 3 gal of pure acid to 2 gal of 50 % acid.
You can use the dilution formulas
Let the volume of pure acid be
∴ You add 3 gal of 100 % acid to 2 gal of 50 % acid.