What should we pay attention to when using volumetric flasks?
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(1) Check for water leakage before use. The procedure is: add water → stand upside down, observe → rotate the stopper 180° → stand upside down, observe.
(2) Volumetric flasks cannot be used to dissolve solutes, let alone stir with glass rods. Therefore, the solute must first be dissolved in the beaker and then transferred to the volumetric flask.
(3) It is not possible to transfer the hot solution to the volumetric flask, let alone to heat the volumetric flask. If the solute is exothermic when it dissolves, you must wait for the solution to cool before pipetting.
(4) To prepare a certain volume of solution, a volumetric flask with the same specification as the volume of the solution must be used. Commonly used are 50mL, 100mL, 250mL, 500mL, 1000mL and other specifications.
(5) Observe whether the added liquid reaches the scale line of the volumetric flask, be sure to look up and make the lowest point of the liquid level just level with the scale line.
(6) If the scale line is exceeded when adding water to a constant volume, the excess part cannot be sucked away, and it must be reconstituted. Although the volume of the solution has reached the requirement, the part of the liquid that is sucked away takes away a part of the solute, which makes the concentration of the prepared solution low.
(7) Volumetric flasks are usually not used to store reagents. Therefore, the prepared solution should be poured into the reagent bottle and labeled.
Post time: Oct-15-2021
