Liquid dispensing method and precautions for plastic volumetric flask
Peeled Garlic Cloves,Roasting Peeled Garlic,Pre Peeled Garlic,Storing Peeled Garlic Jining Yuanheng International Trading Co.,Ltd , https://www.china-garlic-exporter.com
The method of preparing a solution using a plastic volumetric flask is:
(1) Check for leaks at the cork before use. The specific operation method is: put half a bottle of water in the plastic volumetric flask, plug the stopper, use the right index finger to hold the stopper, and the other hand holds the bottom of the volume bottle, and put it upside down (the bottle mouth is facing down), observe Is the volume bottle leaking? If there is no water leakage, the bottle is erected and the stopper is rotated 180°, and then inverted again to check whether there is water leakage. If the operation is performed twice, the bottle around the volume bottle is leaking out, indicating that the volume bottle does not leak. A volumetric bottle that has been checked for leaks can be used.
(2) Place the accurately weighed solid solute in a beaker and dissolve it with a small amount of solvent. The solution is then transferred to a plastic volumetric flask. In order to ensure that all the solute can be transferred to the plastic volumetric flask, the beaker is washed several times with the solvent, and the washing solution is completely transferred to the plastic volumetric flask. Use a glass rod to drain when transferring. The method is to place one end of the glass rod against the inner wall of the plastic capacity bottleneck, taking care not to let other parts of the glass rod touch the volume bottle mouth, prevent liquid from flowing to the outer wall of the volumetric bottle (3) liquid level deviation line added to the plastic volumetric bottle When it is about 1 cm, it should be carefully added with a dropper, and finally the meniscus of the liquid is exactly tangent to the marking. If the water is added above the tick, it will need to be reconstituted.
(4) Close the stopper and mix the liquid in the bottle evenly by inverting and shaking. If the liquid level is lower than the tick mark after standing, this is because a very small amount of solution in the volumetric flask is lost at the bottleneck, so it does not affect the concentration of the prepared solution, so do not add water to the bottle, otherwise it will make Reduced concentration of the prepared solution
Pay attention to the following points when using plastic volumetric flasks:
(1) The volume of the plastic volumetric flask is specific and the scale is not continuous, so one type of volumetric flask can only be prepared with the same volume of solution. Before preparing the solution, first make sure the volume of the solution you need to prepare, and then use the same size of the volumetric flask.
(2) The substance which is easy to dissolve and does not generate heat can be directly dissolved in the plastic volumetric flask by using the funnel. Other substances can hardly dissolve the solute in the volumetric flask. The solute should be dissolved in the beaker and transferred to the volumetric flask.
(3) The total amount of solvent used to wash the beaker shall not exceed the marking of the plastic volumetric flask.
(4) Plastic capacity bottles cannot be heated. If the solute releases heat during the dissolution process, the solution should be cooled after the solution is cooled, because the general volumetric flask is calibrated at a temperature of 20 ° C. If a higher or lower temperature solution is injected into the volumetric flask, the volumetric flask is Will expand and contract, the volume will be inaccurate, resulting in inaccurate concentration of the solution.
(5) The plastic volumetric flask can only be used to prepare the solution, and the solution cannot be stored. Because the solution may corrode the bottle, it is not necessary to weaken the acid and weak base. Note that some organic substances may affect the accuracy of the volumetric flask.
(6) The plastic volumetric flask should be washed in time and, if necessary, sterilized.