Transfer the solution to be diluted to the volumetric flask, then fill the volumetric flask to approximately 3/4 of its total volume.
DO NOT add a stirring bar to the flask (the volume of the stirring bar has not been included in calibration of the flask), but mix the solution well with a gentle swirling motion.
Allow the solution to reach room temperature. The calibration mark on the volumetric flask is made for solutions prepared near room temperature (The temperature that the flask is calibrated for may be printed on the flask).
Once the solution reaches room temperature, slowly add the solvent dropwise with a medicine dropper. Allow enough time between drops for the solvent to flow down the neck of the flask into the bulk of the solution. When the solution nears the calibration mark, the meniscus should be viewed at eye level to eliminate parallax (See the "Reading a Scale" module to learn more about eliminating parallax.) Continue the dropwise addition until the bottom of the meniscus is touching the calibration mark. If too much solvent is added, the solution must be discarded and a new solution should be prepared from the first step of the procedure.