Volumetric flasks are precise instruments for preparing solutions of a certain concentration of substances. It is a slender, pear-shaped flat-bottomed glass flask with a ground-in glass stopper, with one graduation mark on the neck. When the volume of the flask reaches the mark at the specified temperature, its volume is the indicated volume. This kind of flask is usually "metered in". The volumetric flask is marked with temperature, capacity and graduation mark. It is often used in conjunction with pipette. It is mainly used to prepare standard solution, accurate dilution solution and sample solution by direct method. Volumetric flasks are also called measuring flask. Ember volumetric flasks are especially suitable for photosensitive materials. Volumetric flask can be divided into A and B grades according to the allowable tolerance.

Using:

1) Whether the volume of the volumetric flask is consistent with the requirement.

2) In order to check whether the flask stopper is tight and not leaking.Specific operation: Put water in the flask near the marking line, tighten the flask stopper, make it stand upside down for 2 minutes, and check with dry filter paper along the gap of the flask mouth to see if there is water leakage. If there is no leakage, then rotate the stopper 180 degrees, plug tightly, invert, test whether there is leakage in this direction.It is necessary to do two checks because sometimes the stopper and the mouth of the flask are not always close at any position. Close-fitting flask stoppers must be properly protected. It is best to tie them to the flask neck with a rope to prevent them from falling apart or being confused with other volumetric flasks.

Attention:

1. Solutions can not be dissolved in volumetric flasks. Solutions should be dissolved in beakers and transferred to volumetric flasks.

2. The total amount of solvent used for washing beakers should not exceed the label of the volumetric flask. Once exceeded, it must be redeployed.

3. Volumetric flask cannot be heated. If the solute is exothermic in the dissolution process, it will be transferred after the solution is cooled, because the volume of the flask will be inaccurate when the temperature rises.

4. Volumetric flask can only be used to prepare solutions, not to store solutions for a long time, because the solution may corrode the flask body, thus affecting the accuracy of the volumetric flask.

5.The volumetric flask should be cleaned in time, plugged with the stopper, and a scrap between the stopper and the flask mouth should be inserted to prevent the stopper from adhering to the flask mouth.

6.The volumetric flask can only prepare a certain volume of solution, but generally retains four significant digits (e.g. 250.0ml). It can not estimate the number behind decimal point because the solution exceeds or fails to reach the mark line. It can only be reconfigured. Therefore, the volume of writing solution must be XXX.0ml.

Grade: A grade, B grade

Glass: clear glass, ember glass