I read today that the FAA has extended the timeline in which it will be inspecting all charter operations specifications section A008 for compliance with operational control requirements.
We have three sizes of volumetric flasks to choose from: 100, 250 and 500 milliliters and they feature a single etched line or graduation to denote the fill-to-line at the chosen volume. Each size flask is specifically made for preparing solutions that correspond to its nominal value. For example, a 250 ml volumetric flask is the appropriate choice only when preparing a solution with a total volume of 250 ml.
We don't won't to put the stopper on the flask just yet. There is about 25 mL of air (80% nitrogen & 20% oxygen) in the flask. The bubbles of oxygen that are forming will displace the air by pushing it out of the flask. Oxygen is a little more dense than air, so oxygen will stay closer to the surface of the water and push the air out of the flask. Wait about 2 minutes before placing the stopper onto the flask. That will give the newly created oxygen to push the most of the air out of the flask.