[Capacity Bottle]

Volumetric flasks are mainly used to accurately prepare solutions with a certain molar concentration. It is a slender neck, pear shaped flat bottomed glass bottle with a ground stopper. The bottleneck is marked with a line, and when the liquid inside the bottle reaches the marked area at the specified temperature, its volume is the volume indicated on the bottle. A volumetric flask of a certain specification can only take one amount of energy. The commonly used volumetric flasks come in various sizes such as 100, 250, 500 milliliters, etc.

The method of preparing a solution using a volumetric flask is:

(1) Check for water leakage at the bottle stopper before use. The specific operation method is to fill half a bottle of water into the volumetric flask, tighten the bottle stopper, hold the bottle stopper with the index finger of the right hand, and hold the bottom of the volumetric flask with the five fingers of the other hand. Invert it (with the bottle mouth facing down) and observe whether the volumetric flask leaks water. If there is no water leakage, stand the bottle upright and rotate the bottle stopper 180 °, then invert it again to check for water leakage. If there is no water leakage around the stopper of the volumetric flask after two operations, it indicates that the volumetric flask is not leaking. Only volumetric flasks that have been inspected and found to be leak proof can be used.
(2) Place the accurately weighed solid solute in a beaker and dissolve it in a small amount of solvent. Then transfer the solution to a volumetric flask. To ensure that all solutes can be transferred to the volumetric flask, the beaker should be washed multiple times with solvent and all washing solutions should be transferred to the volumetric flask. When transferring, a glass rod should be used for drainage. The method is to place one end of the glass rod against the inner wall of the capacity bottle neck, being careful not to let other parts of the glass rod touch the mouth of the capacity bottle to prevent liquid from flowing onto the outer wall of the capacity bottle
(3) When the liquid level added to the volumetric flask is about 1 centimeter away from the marking line, a dropper should be used to carefully drip the liquid until the meniscus of the liquid is perfectly tangent to the marking line. If the water addition exceeds the scale line, it needs to be reconfigured.
(4) Tighten the bottle stopper and mix the liquid in the bottle evenly by reversing and shaking. If the liquid level is found to be lower than the scale line after standing still, it is because a very small amount of solution in the volumetric flask has been lost due to wetting at the bottleneck, so it does not affect the concentration of the prepared solution. Therefore, do not add water to the flask, otherwise it will reduce the concentration of the prepared solution.

When using a volumetric flask, the following points should be noted:

(1) The volume of a volumetric flask is specific and the scale is not continuous, so only the same volume of solution can be prepared for one type of volumetric flask. Before preparing the solution, it is necessary to first determine the volume of the solution to be prepared, and then select a volumetric flask of the same specification.
(2) Substances that are easily soluble and do not generate heat can be directly dissolved in a volumetric flask using a funnel. Other substances cannot be dissolved as solutes in a volumetric flask and should be transferred to the flask after being dissolved in a beaker.
(3) The total amount of solvent used for washing the beaker cannot exceed the marking on the volumetric flask.
(4) The volumetric flask cannot be heated. If the solute releases heat during the dissolution process, it should be transferred after the solution has cooled down, because a typical volumetric flask is calibrated at a temperature of 20 ℃. If a solution with a higher or lower temperature is injected into the volumetric flask, the flask will expand and contract, and the measured volume will be inaccurate, resulting in inaccurate concentration of the prepared solution.
(5) Volumetric flasks can only be used for preparing solutions and cannot store solutions, as the solution may corrode the bottle body, thereby affecting the accuracy of the volumetric flask.
(6) After using the volumetric flask, it should be washed clean in a timely manner, the cork should be added, and a piece of paper should be sandwiched between the cork and the bottle mouth to prevent the cork from sticking to the bottle mouth.