Under the chemical hood, place a stirring plate, 2 L glass beaker and a magnetic stir bar.
Use a cylinder to measure 242 ml of dH2O and pour in the beaker.
Start stirring (slow speed).
Use a glass cylinder to measure 758 mL of H2SO4 and SLOWLY pour into the beaker.
Wait at least 1 h to for the solution to cool down.
In a 1 L glass cylinder, adjust the final volume to 1 L with dH2O.
When completely cooled, aliquot in 250 ml bottles.